@article{lavoie_rojas_khan_shim_2024, title={Charge Protection in Electret Air Filtration Nonwoven Materials}, volume={4}, ISSN={["2365-709X"]}, url={https://doi.org/10.1002/admt.202301670}, DOI={10.1002/admt.202301670}, abstractNote={Abstract}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Lavoie, Joseph and Rojas, Orlando J. and Khan, Saad A. and Shim, Eunkyoung}, year={2024}, month={Apr} }
 @article{sarker_su_rojas_khan_2024, title={Colloidal interactions between nanochitin and surfactants: Connecting micro- and macroscopic properties by isothermal titration calorimetry and rheology}, volume={341}, ISSN={["1879-1344"]}, DOI={10.1016/j.carbpol.2024.122341}, abstractNote={This study elucidates the intricate interactions between chitin nanocrystals (ChNC) and surfactants of same hydrophobic tail (C12) but different head groups types (anionic, cationic, nonionic): sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB), and polyoxyethylene(23)lauryl ether (Brij-35). Isothermal Titration Calorimetry (ITC) and rheology are used to study the complex ChNC-surfactant interactions in aqueous media, affected by adsorption, self-assembly and micellization. The ITC results demonstrate that the surfactant head group significantly influences the dynamics and nature of the involved phenomena. Cationic DTAB's reveal minimal interaction with ChNC, non-ionic Brij-25's interact moderately at low concentrations driven by hydrophobic effects while SDS's interacts strongly and show complex interaction patterns that fall across four distinct regimes with SDS addition. We attribute such behavior to initiate through electrostatic attraction and terminate in surfactant micelle formation on ChNC surfaces. ITC also elucidates the impact of ChNC concentration on key parameters including critical aggregation concentration (CAC) and saturation concentration (C2). Dynamic rheological analysis indicates the molecular interactions translate to non-linear variations in the elastic modulus (G') upon SDS addition mirroring that observed in ITC experiments. Such a direct correlation between molecular interactions and macroscopic rheological properties provides insights to aid in the creation of nanocomposites with tailored properties.}, journal={CARBOHYDRATE POLYMERS}, author={Sarker, Prottasha and Su, Xiaoya and Rojas, Orlando J. and Khan, Saad A.}, year={2024}, month={Oct} }
 @article{sarker_jani_hsiao_rojas_khan_2023, title={Interacting collagen and tannic acid Particles: Uncovering pH-dependent rheological and thermodynamic behaviors}, volume={650}, ISSN={0021-9797}, url={http://dx.doi.org/10.1016/j.jcis.2023.06.209}, DOI={10.1016/j.jcis.2023.06.209}, abstractNote={Biomaterials such as collagen and tannic acid (TA) particles are of interest in the development of advanced hybrid biobased systems due to their beneficial therapeutic functionalities and distinctive structural properties. The presence of numerous functional groups makes both TA and collagen pH responsive, enabling them to interact via non-covalent interactions and offer tunable macroscopic properties.The effect of pH on the interactions between collagen and TA particles is explored by adding TA particles at physiological pH to collagen at both acidic and neutral pH. Rheology, isothermal titration calorimetry (ITC), turbidimetric analysis and quartz crystal microbalance with dissipation monitoring (QCM-D) are used to study the effects.Rheology results show significant increase in elastic modulus with an increase in collagen concentration. However, TA particles at physiological pH provide stronger mechanical reinforcement to collagen at pH 4 than collagen at pH 7 due to the formation of a higher extent of electrostatic interaction and hydrogen bonding. ITC results confirm this hypothesis, with larger changes in enthalpy, |ΔH|, observed when collagen is at acidic pH and |ΔH| > |TΔS| indicating enthalpy-driven collagen-TA interactions. Turbidimetric analysis and QCM-D help to identify structural differences of the collagen-TA complexes and their formation at both pH conditions.}, journal={Journal of Colloid and Interface Science}, publisher={Elsevier BV}, author={Sarker, Prottasha and Jani, Pallav K. and Hsiao, Lilian C. and Rojas, Orlando J. and Khan, Saad A.}, year={2023}, month={Nov}, pages={541–552} }
 @article{elsherbiny_abdelgawad_el-naggar_hemdan_ghazanfari_jockenhoevel_rojas_2022, title={Bioactive tri-component nanofibers from cellulose acetate/lignin// N-vanillidene-phenylthiazole copper-(II) complex for potential diaper dermatitis control}, volume={205}, ISSN={["1879-0003"]}, DOI={10.1016/j.ijbiomac.2022.02.192}, abstractNote={Current research targets innovative medical textiles of nanofibrous nature and antibacterial activity to prevent diaper dermatitis. The work is based on electrospun nanofibers from cellulose acetate (CA) and lignin (Lig) polymers. A series of new copper complexes were synthesized and loaded to the CA/Lig solution mix then subjected to electrospinning, giving rise to the tricomponent bioactive mats CA/Lig/Cu-complex. The surface morphology of electrospun nanofiber mats was smooth and homogenous as the concentration of lignin increased in the mixture. The incorporation of lignin improved the electrospinnability of the cellulose acetate; however, it increased the fiber diameter. The water contact angle, absorption underload were significantly improved as lignin content increased. The incorporation of Cu-complex in electrospun CA and CA/Lig fiber mats occurred without any substantial change in the surface morphology, indicating well encapsulation of the complex. The electrospun mats were active against Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus epidermidis, and Streptococcus faecalis. The cytotoxicity, protein leakage, and biological results, together with the above studies, would advocate copper complex loaded CA/Lig nanofibers as a potential candidate for hygienic applications.}, journal={INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES}, author={Elsherbiny, Dalia A. and Abdelgawad, Abdelrahman M. and El-Naggar, Mehrez E. and Hemdan, Bahaa A. and Ghazanfari, Samaneh and Jockenhoevel, Stefan and Rojas, Orlando J.}, year={2022}, month={Apr}, pages={703–718} }
 @article{sarker_nalband_freytes_rojas_khan_2022, title={High-Axial-Aspect Tannic Acid Microparticles Facilitate Gelation and Injectability of Collagen-Based Hydrogels}, volume={10}, ISSN={["1526-4602"]}, url={https://doi.org/10.1021/acs.biomac.2c00916}, DOI={10.1021/acs.biomac.2c00916}, abstractNote={Injectable collagen-based hydrogels offer great promise for tissue engineering and regeneration, but their use is limited by poor mechanical strength. Herein, we incorporate tannic acid (TA) to tailor the rheology of the corresponding hydrogels while simultaneously adding the therapeutic benefits inherent to this polyphenolic component. TA in the solution form and needle-shaped TA microparticles are combined with collagen and the respective systems studied for their time-dependent sol-gel transitions (from storage to body temperatures, 4-37 °C) as a function of TA concentration. Compared to systems incorporating TA microparticles, those with dissolved TA, applied at a similar concentration, generate a less significant enhancement of the elastic modulus. Premature gelation at a low temperature and associated colloidal arrest of the system are proposed as a main factor explaining this limited performance. A higher yield stress (elastic stress method) is determined for systems loaded with TA microparticles compared to the system with dissolved TA. These results are interpreted in terms of the underlying interactions of TA with collagen, as probed by spectroscopy and isothermal titration calorimetry. Importantly, hydrogels containing TA microparticles show high cell viability (human dermal fibroblasts) and comparative cellular activity relative to the collagen-only hydrogel. Overall, composite hydrogels incorporating TA microparticles demonstrate a new, simple, and better-performance alternative to cell culturing and difficult implantation scenarios.}, journal={BIOMACROMOLECULES}, author={Sarker, Prottasha and Nalband, Danielle M. and Freytes, Donald O. and Rojas, Orlando J. and Khan, Saad A.}, year={2022}, month={Oct} }
 @article{jin_kamarainen_rinke_rojas_todorovic_2022, title={Machine learning as a tool to engineer microstructures: Morphological prediction of tannin-based colloids using Bayesian surrogate models}, ISSN={["1938-1425"]}, DOI={10.1557/s43577-021-00183-4}, abstractNote={
                Abstract
                Oxidized tannic acid (OTA) is a useful biomolecule with a strong tendency to form complexes with metals and proteins. In this study we open the possibility to further the application of OTA when assembled as supramolecular systems, which typically exhibit functions that correlate with shape and associated morphological features. We used machine learning (ML) to selectively engineer OTA into particles encompassing one-dimensional to three-dimensional constructs. We employed Bayesian regression to correlate colloidal suspension conditions (pH and pKa) with the size and shape of the assembled colloidal particles. Fewer than 20 experiments were found to be sufficient to build surrogate model landscapes of OTA morphology in the experimental design space, which were chemically interpretable and endowed predictive power on data. We produced multiple property landscapes from the experimental data, helping us to infer solutions that would satisfy, simultaneously, multiple design objectives. The balance between data efficiency and the depth of information delivered by ML approaches testify to their potential to engineer particles, opening new prospects in the emerging field of particle morphogenesis, impacting bioactivity, adhesion, interfacial stabilization, and other functions inherent to OTA.
              }, journal={MRS BULLETIN}, author={Jin, Soo-Ah and Kamarainen, Tero and Rinke, Patrick and Rojas, Orlando J. and Todorovic, Milica}, year={2022}, month={Feb} }
 @article{jin_khan_spontak_rojas_2021, title={Anion-Specific Water Interactions with Nanochitin: Donnan and Osmotic Pressure Effects as Revealed by Quartz Microgravimetry}, volume={37}, ISSN={["0743-7463"]}, url={https://doi.org/10.1021/acs.langmuir.1c01585}, DOI={10.1021/acs.langmuir.1c01585}, abstractNote={The development of new materials emphasizes greater use of sustainable and eco-friendly resources, including those that take advantage of the unique properties of nanopolysaccharides. Advances in this area, however, necessarily require a thorough understanding of interactions with water. Our contribution to this important topic pertains to the swelling behavior of partially deacetylated nanochitin (NCh), which has been studied here by quartz crystal microgravimetry. Ultrathin films of NCh supported on gold-coated resonators have been equilibrated in aqueous electrolyte solutions (containing NaF, NaCl, NaBr, NaNO3, Na2SO4, Na2SO3, or Na3PO4) at different ionic strengths. As anticipated, NCh displays contrasting swelling/deswelling responses, depending on the ionic affinities and valences of the counterions. The extent of water uptake induced by halide anions, for instance, follows a modified Hofmeister series with F– producing the highest swelling. In marked contrast, Cl– induces film dehydration. We conclude that larger anions promote deswelling such that water losses increase with increasing anion valence. Results such as the ones reported here are critical to ongoing efforts designed to dry chitin nanomaterials and develop bio-based and sustainable materials, including particles, films, coatings, and other nanostructured assemblies, for various devices and applications.}, number={38}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Jin, Soo-Ah and Khan, Saad A. and Spontak, Richard J. and Rojas, Orlando J.}, year={2021}, month={Sep}, pages={11242–11250} }
 @article{facchine_bai_rojas_khan_2021, title={Associative structures formed from cellulose nanofibrils and nanochitins are pH-responsive and exhibit tunable rheology}, volume={588}, ISSN={["1095-7103"]}, url={https://doi.org/10.1016/j.jcis.2020.12.041}, DOI={10.1016/j.jcis.2020.12.041}, abstractNote={Nanocellulose and nanochitin are both biobased materials with complementary structures and properties. Both exhibit pH-dependent surface charges which are opposite in sign. Hence, it should be possible to manipulate them to form complexed structures via ionic bond formation at prescribed pH conditions.Nanocellulose and nanochitin were mixed after exposure to acidic or neutral conditions to influence their ionization state. The heat of interaction during the introduction of nanochitin to nanocellulose was monitored via isothermal titration calorimetry. The strength and gel properties of the resulting structures were characterized via rheological measurement.The resultant gel properties in the designed hybrid systems were found to depend directly on the charge state of the starting materials, which was dictated by pH adjustment. Different interparticle interactions including ionic attraction, hydrophobic associations, and physical entanglement were identified in the systems and the influence of each was elucidated for different conditions of pH, concentration, and ratio of nanochitin to nanocellulose. Hydrophobic associations between neutralized nanochitin particles were found to contribute strongly to increased elastic modulus values. Ionic complex formation was found to provide enhanced stability under broader pH conditions, while physical entanglement of cellulose nanofibers was a substantial thickening mechanism in all systems.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Facchine, Emily G. and Bai, Long and Rojas, Orlando J. and Khan, Saad A.}, year={2021}, month={Apr}, pages={232–241} }
 @article{jin_facchine_rojas_khan_spontak_2021, title={Cellulose nanofibers and the film-formation dilemma: Drying temperature and tunable optical, mechanical and wetting properties of nanocomposite films composed of waterborne sulfopolyesters}, volume={598}, ISSN={["1095-7103"]}, url={https://doi.org/10.1016/j.jcis.2021.04.032}, DOI={10.1016/j.jcis.2021.04.032}, abstractNote={Waterborne sulfopolyesters have gained considerable interest as coating materials due to their excellent film-forming and optical properties. Their commercial use has been limited, however, due to their fragile nature. Incorporating cellulose nanofiber (CNF), a sustainable biopolymer, into the polymer matrix is expected to enhance the mechanical integrity of the nanocomposite as these two components synergistically interact. In this study, we have investigated the suspension and film characteristics of three sulfopolyesters varying in charge density, glass transition temperature and molecular weight, as well as their mixtures with CNF. We have performed steady-shear rheology on mixtures with different CNF loading levels, and resulting films have been subjected to quasistatic uniaxial tensile and water contact-angle tests to elucidate the effects of CNF on mechanical and surface properties. Addition of CNF to waterborne polyester promotes shear-thinning behavior that remains unaffected by the CNF content. Solid films cast from these suspensions possess enhanced mechanical properties, as well as tailorable surface hydrophilicity, depending on composition and film-drying temperature. Tensile tests reveal that films containing 10 wt% CNF display the greatest mechanical improvements, suggesting the existence of a previously unidentified Goldilocks composition window.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, publisher={Elsevier BV}, author={Jin, Soo-Ah and Facchine, Emily G. and Rojas, Orlando J. and Khan, Saad A. and Spontak, Richard J.}, year={2021}, month={Sep}, pages={369–378} }
 @article{kaschuk_borghei_solin_tripathi_khakalo_leite_branco_sousa_frollini_rojas_2021, title={Cross-Linked and Surface-Modified Cellulose Acetate as a Cover Layer for Paper-Based Electrochromic Devices}, volume={3}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.0c01252}, abstractNote={We studied the surface and microstructure of cellulose acetate (CA) films to tailor their barrier and mechanical properties for application in electrochromic devices (ECDs). Cross-linking of CA was carried out with pyromellitic dianhydride to enhance the properties relative to unmodified CA: solvent resistance (by 43% in acetone and 37% in DMSO), strength (by 91% for tensile at break), and barrier (by 65% to oxygen and 92% to water vapor). Surface modification via tetraethyl orthosilicate and octyltrichlorosilane endowed the films with hydrophobicity, stiffness, and further enhanced solvent resistance. A detailed comparison of structural, chemical, surface, and thermal properties was performed by using X-ray diffraction, dynamic mechanical analyses, Fourier-transform infrared spectroscopy, and atomic force microscopy. Coplanar ECDs were synthesized by incorporating a hydrogel electrolyte comprising TEMPO-oxidized cellulose nanofibrils and an ionic liquid. When applied as the top layer in the ECDs, cross-linked and hydrophobized CA films extended the functionality of the assembled displays. The results indicate excellent prospects for CA films in achieving environmental-friendly ECDs that can replace poly(ethylene terephthalate)-based counterparts.}, number={5}, journal={ACS APPLIED POLYMER MATERIALS}, author={Kaschuk, Joice Jaqueline and Borghei, Maryam and Solin, Katariina and Tripathi, Anurodh and Khakalo, Alexey and Leite, Fabio A. S. and Branco, Aida and Sousa, Miriam C. Amores and Frollini, Elisabete and Rojas, Orlando J.}, year={2021}, month={May}, pages={2393–2401} }
 @article{tyagi_gutierrez_nathani_lucia_rojas_hubbe_pal_2021, title={Hydrothermal and mechanically generated hemp hurd nanofibers for sustainable barrier coatings/films}, volume={168}, ISSN={["1872-633X"]}, url={https://doi.org/10.1016/j.indcrop.2021.113582}, DOI={10.1016/j.indcrop.2021.113582}, abstractNote={Residual hemp (Cannabis sativa) hurd fibers obtained from hydrothermal, carbonate, and kraft treatments were the resources used to obtain lignocellulosic nanofibers (LCNF) by using an ultra-fine friction grinder. The morphological, crystallinity, and chemical characteristics of the nanocellulose films were carried out using SEM, XRD, EDX and ToF-SIMS. Water barrier properties of the same were measured in terms of water contact angle, water vapor permeability (WVP) and water absorption. The barrier properties were found to be dependent not only on the lignin content and lignin distribution, but also on the film density and porous structure. LCNF films and coatings showed much higher water contact angle (WCA) (80°-102°) than films produced from the bleached CNF. WVP was found to be more dependent on the density of films than lignin content. Overall, LCNF-based films and coatings derived from hemp hurd residual fibers can contribute to a circular economy and sustainability.}, journal={INDUSTRIAL CROPS AND PRODUCTS}, publisher={Elsevier BV}, author={Tyagi, Preeti and Gutierrez, Joseph N. and Nathani, Ved and Lucia, Lucian A. and Rojas, Orlando J. and Hubbe, Martin A. and Pal, Lokendra}, year={2021}, month={Sep} }
 @article{adhikari_jani_hsiao_rojas_khan_2021, title={Interfacial Contributions in Nanodiamond-Reinforced Polymeric Fibers}, volume={125}, ISSN={["1520-5207"]}, url={https://doi.org/10.1021/acs.jpcb.1c03361}, DOI={10.1021/acs.jpcb.1c03361}, abstractNote={We study the interfacial energy parameters that explain the reinforcement of polymers with nanodiamond (ND) and the development of mechanical strength of electrospun ND-reinforced composites. Thermodynamic parameters such as the wettability ratio, work of spreading and dispersion/aggregation transition are used to derive a criterion to predict the dispersibility of carboxylated ND (cND) in polymeric matrices. Such a criterion for dispersion (Dc) is applied to electrospun cND-containing poly(vinyl alcohol) (PVA), polyacrylonitrile (PAN), and polystyrene (PS) fiber composites. The shifts in glass transition temperature (ΔTg), used as a measure of polymer/cND interfacial interactions and hence the reinforcement capability of cNDs, reveal a direct correlation with the thermodynamic parameter Dc in the order of PAN < PS < PVA. Contrary to expectation, however, the tensile strength of the electrospun fibers correlates with the Dc and ΔTg only for semicrystalline polymers (PAN < PVA) while the amorphous PS displays a maximum reinforcement with cND. Such conflicting results reveal a synergy that is not captured by thermodynamic considerations alone but also factor in the contributions of polymer/cND interface stress transfer efficiency. Our findings open the possibility for tailoring the interfacial interactions in polymer-ND fiber composites to achieve maximum mechanical reinforcement.}, number={36}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society (ACS)}, author={Adhikari, Prajesh and Jani, Pallav K. and Hsiao, Lilian C. and Rojas, Orlando J. and Khan, Saad A.}, year={2021}, month={Sep}, pages={10312–10323} }
 @article{jin_facchine_khan_rojas_spontak_2021, title={Mesophase characteristics of cellulose nanocrystal films prepared from electrolyte suspensions}, volume={599}, ISSN={["1095-7103"]}, url={https://doi.org/10.1016/j.jcis.2021.04.071}, DOI={10.1016/j.jcis.2021.04.071}, abstractNote={Cellulose nanocrystals (CNCs) exhibit a cholesteric mesophase above a critical concentration in aqueous suspensions. Above this concentration, CNCs self-organize into left-handed helicoidal structures that can be preserved in dried, stratified films. In this systematic study, we have prepared optically-active CNC films cast from different electrolyte suspensions and investigated, via circular dichroism and other techniques, the effects of counterion type (six mono/divalent salts, including those responsible for promoting "salting-out" and "salting-in" in the Hofmeister series) and ionic strength on mesomorphic behavior and cholesteric arrangement. The presence of electrolytes influences CNC colloidal stability by compressing the electric double layer and altering interactions among neighboring CNCs and water, thereby affecting the extent to which the CNCs form a mesophase. Interestingly, mesomorphic behavior and CNC alignment appear to be sensitive to cationic radius and charge valence, in which case the optical properties of CNC films can be adjusted for targeted sustainable applications. Such heuristic rules can be valuable for predicting the stability and characteristics of CNC microstructure in designer coatings and thin films prepared by introducing suitable cations prior to film formation.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, publisher={Elsevier BV}, author={Jin, Soo-Ah and Facchine, Emily G. and Khan, Saad A. and Rojas, Orlando J. and Spontak, Richard J.}, year={2021}, month={Oct}, pages={207–218} }
 @article{zambrano_wang_zwilling_venditti_jameel_rojas_gonzalez_2021, title={Micro- and nanofibrillated cellulose from virgin and recycled fibers: A comparative study of its effects on the properties of hygiene tissue paper}, volume={254}, ISSN={0144-8617}, url={http://dx.doi.org/10.1016/j.carbpol.2020.117430}, DOI={10.1016/j.carbpol.2020.117430}, abstractNote={This study aims to understand the effect of micro- and nanofibrillated cellulose (MNFC) on the tensile index, softness, and water absorbency of tissue paper. MNFC was produced from four different fiber sources. The results show that MNFC acts as an effective strength enhancer at the expense of a reduced water absorbency and softness. The impact of the fiber source on MNFC manufacturing cost and the trade-off with performance was also investigated. MNFCs produced from southern bleached hardwood kraft, northern bleached softwood kraft, and deinked pulp exhibited similar performance trends with the MNFC from the deinked pulp having a significantly lower cost. This suggests that MNFCs with similar degrees of fibrillation may be used interchangeably regardless of the fiber source, revealing the possibility to minimize MNFC manufacturing costs based on fiber selection. MNFC produced from bleached Eucalyptus kraft showed the lowest degree of fibrillation and the lowest strength improvements among the MNFCs evaluated.}, journal={Carbohydrate Polymers}, publisher={Elsevier BV}, author={Zambrano, Franklin and Wang, Yuhan and Zwilling, Jacob D. and Venditti, Richard and Jameel, Hasan and Rojas, Orlando and Gonzalez, Ronalds}, year={2021}, month={Feb}, pages={117430} }
 @article{ma_lu_wang_hubbe_liu_mu_wang_sun_rojas_2021, title={Recent developments in colorimetric and optical indicators stimulated by volatile base nitrogen to monitor seafood freshness}, volume={28}, ISSN={["2214-2894"]}, DOI={10.1016/j.fpsl.2021.100634}, abstractNote={Seafood spoilage could cause food waste and also serious foodborne disease because of the specific organisms and their metabolites. Therefore, it is important to monitor their freshness in the supply chain. In most cases, their spoilage has been determined by the content of volatile base nitrogen, adenosine triphosphate or the total viable count. However, these destructive detection methods are tedious and time consuming. Hence, it is highly desirable to develop easily operated and non-destructive sensing technologies for real-time detection. A lot of freshness indicators have emerged up to now. Colorimetric indicators are particularly beneficial to accompany use-by dates in food packaging as real-time indicators because they produce visible color changes to the naked eye, which can be easily understood by consumers and non-specialists. Numerous studies have considered the colorimetric indicators to monitor seafood freshness in recent years. This paper mainly focused on colorimetric indicators stimulated by volatile base nitrogen. The most traditional materials used in these indicators are also discussed. The challenges and opportunities in the systems are introduced in this context as well based on the published literature.}, journal={FOOD PACKAGING AND SHELF LIFE}, author={Ma, Qianyun and Lu, Xiaomin and Wang, Wenxiu and Hubbe, Martin A. and Liu, Yaqiong and Mu, Jianlou and Wang, Jie and Sun, Jianfeng and Rojas, Orlando J.}, year={2021}, month={Jun} }
 @article{zwilling_jiang_zambrano_venditti_jameel_velev_rojas_gonzalez_2021, title={Understanding lignin micro- and nanoparticle nucleation and growth in aqueous suspensions by solvent fractionation}, volume={23}, ISSN={1463-9262 1463-9270}, url={http://dx.doi.org/10.1039/D0GC03632C}, DOI={10.1039/d0gc03632c}, abstractNote={Interactions of sub-micron lignin particles dependent on precursor kraft lignin chemistry and molecular weight.}, number={2}, journal={Green Chemistry}, publisher={Royal Society of Chemistry (RSC)}, author={Zwilling, Jacob D. and Jiang, Xiao and Zambrano, Franklin and Venditti, Richard A. and Jameel, Hasan and Velev, Orlin D. and Rojas, Orlando J. and Gonzalez, Ronalds}, year={2021}, pages={1001–1012} }
 @article{tripathi_tardy_khan_liebner_rojas_2019, title={Expanding the upper limits of robustness of cellulose nanocrystal aerogels: outstanding mechanical performance and associated pore compression response of chiral-nematic architectures}, volume={7}, ISSN={["2050-7496"]}, DOI={10.1039/c9ta03950c}, abstractNote={Anisotropy in liquid crystal dispersions of cellulose nanocrystals is demonstrated to drastically enhance the mechanical attributes of derived aerogels.}, number={25}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Tripathi, Anurodh and Tardy, BlaiseL. and Khan, Saad A. and Liebner, Falk and Rojas, Orlando J.}, year={2019}, month={Jul}, pages={15309–15319} }
 @article{park_yoo_lim_rojas_hubbe_park_2019, title={Impact of oxidative carbonization on structure development of loblolly pine-derived biochar investigated by nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy}, volume={96}, ISSN={["1879-0062"]}, DOI={10.1016/j.diamond.2019.05.001}, abstractNote={Biochar produced at an oxidative atmosphere shows distinct chemical properties compared to those of biochar produced at an inert atmosphere. However, there has been little investigation on the relationship between the oxidative atmosphere and the structure development of biochar, which can be useful information for the utilization of derived products. In this study, the effect of the oxygen atmosphere on the structure development of loblolly pine-derived biochar during thermal treatment was investigated. Quantitative analysis using solid-state direct polarization/magic angle spinning 13C nuclear magnetic resonance spectroscopy presented the existence of large fractions of aromatic and non-protonated carbons in the biochars treated at an oxidative atmosphere, implying highly condensed aromatic structures with large cluster sizes. Simultaneous thermogravimetic analyzer-differential scanning calorimetry was employed to demonstrate the difference in heat flow during the thermal treatment at two different atmospheres. Relatively large exothermic heat flow was observed when woody biomass was treated at 350 °C under an oxidative atmosphere which might be responsible for the difference in structural alteration. The series of observations suggested that compared to inert atmospheric conditions, admitting a limited amount of oxygen during thermal treatment of woody biomass could promote the evolution of condensed aromatic carbon structures.}, journal={DIAMOND AND RELATED MATERIALS}, author={Park, Junyeong and Yoo, Seunghyun and Lim, Kwang Hun and Rojas, Orlando J. and Hubbe, Martin A. and Park, Sunkyu}, year={2019}, month={Jun}, pages={140–147} }
 @article{islam_gurgel_rojas_carbonell_2019, title={Use of a Branched Linker for Enhanced Biosensing Properties in IgG Detection from Mixed Chinese Hamster Ovary Cell Cultures}, volume={30}, ISSN={["1043-1802"]}, DOI={10.1021/acs.bioconjchem.8b00918}, abstractNote={Tris(2-aminoethyl)-amine (TREN), a branched amine, was coupled to planar surfaces of alkanethiol self-assembled monolayers (SAMs) to increase the grafting density of IgG-binding peptide (HWRGWV or HWRGWVG) on gold surfaces. One of the three primary amine pendant groups of TREN anchors onto the SAM, while the other two are available for grafting with the C-termini of the peptide. The ellipsometric peptide density on the SAM-branched amine was 1.24 molecules nm-2. The surfaces carrying the peptides were investigated via surface plasmon resonance (SPR) to quantify the adsorption of IgG and showed maximum binding capacity, Qm of 4.45 mg m-2, and dissociation constant, Kd of 8.7 × 10-7 M. Real-time dynamic adsorption data was used to determine adsorption rate constants, ka values, and the values were dependent on IgG concentration. IgG binding from complex mixtures of Chinese hamster ovary supernatant (CHO) was investigated and regeneration studies were carried out. Compared to the unbranched amine-based surfaces, the branched amines increased the overall sensitivity and selectivity for IgG adsorption from complex mixtures. Regeneration of the branched amine-based surfaces was achieved with 0.1 M NaOH, with less than 10% decline in peptide activity after 12 cycles of regeneration-binding.}, number={3}, journal={BIOCONJUGATE CHEMISTRY}, author={Islam, Nafisa and Gurgel, Patrick V. and Rojas, Orlando J. and Carbonell, Ruben G.}, year={2019}, month={Mar}, pages={815–825} }
 @article{xie_khan_rojas_parsons_2018, title={Control of Micro- and Mesopores in Carbon Nanofibers and Hollow Carbon Nanofibers Derived from Cellulose Diacetate via Vapor Phase Infiltration of Diethyl Zinc}, volume={6}, ISSN={["2168-0485"]}, url={https://doi.org/10.1021/acssuschemeng.8b02014}, DOI={10.1021/acssuschemeng.8b02014}, abstractNote={Common thermoplastic polymers, such as poly(vinyl alcohol) and cellulose derivatives are abundant and inexpensive precursors for preparing carbon nanofibers. These polymers are soluble in common solvents and can be readily processed to prepare nanofibers with high external surface area. However, thermoplastic polymers undergo a melting transition upon heating, resulting in loss of initial morphology and low carbon yield. In this study, vapor infiltration of diethyl zinc (DEZ) is applied to modify electrospun cellulose diacetate (CDA) nanofibers before carbonization, resulting in excellent retention of the original fiber structure while maintaining a high surface area and pore size distribution. Our goal is to investigate the effect of inorganic modification on the morphology and structural properties of the carbon product from the CDA nanofibers. We found that the CDA nanofiber structure was preserved after incorporation of ∼10 wt % Zn by vapor infiltration of DEZ. In addition, we found the pore volume di...}, number={11}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, publisher={American Chemical Society (ACS)}, author={Xie, Wenyi and Khan, Saad and Rojas, Orlando J. and Parsons, Gregory N.}, year={2018}, month={Nov}, pages={13844–13853} }
 @article{klockars_tardy_borghei_tripathi_greca_rojas_2018, title={Effect of Anisotropy of Cellulose Nanocrystal Suspensions on Stratification, Domain Structure Formation, and Structural Colors}, volume={19}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.8b00497}, abstractNote={Outstanding optical and mechanical properties can be obtained from hierarchical assemblies of nanoparticles. Herein, the formation of helically ordered, chiral nematic films obtained from aqueous suspensions of cellulose nanocrystals (CNCs) were studied as a function of the initial suspension state. Specifically, nanoparticle organization and the structural colors displayed by the resultant dry films were investigated as a function of the anisotropic volume fraction (AVF), which depended on the initial CNC concentration and equilibration time. The development of structural color and the extent of macroscopic stratification were studied by optical and scanning electron microscopy as well as UV–vis spectroscopy. Overall, suspensions above the critical threshold required for formation of liquid crystals resulted in CNC films assembled with longer ranged order, more homogeneous pitches along the cross sections, and narrower specific absorption bands. This effect was more pronounced for the suspensions that were closer to equilibrium prior to drying. Thus, we show that high AVF and more extensive phase separation in CNC suspensions resulted in large, long-range ordered chiral nematic domains in dried films. Additionally, the average CNC aspect ratio and size distribution in the two separated phases were measured and correlated to the formation of structured domains in the dried assemblies.}, number={7}, journal={BIOMACROMOLECULES}, author={Klockars, Konrad W. and Tardy, Blaise L. and Borghei, Maryam and Tripathi, Anurodh and Greca, Luiz G. and Rojas, Orlando J.}, year={2018}, month={Jul}, pages={2931–2943} }
 @article{tripathi_ago_khan_rojas_2018, title={Heterogeneous Acetylation of Plant Fibers into Micro- and Nanocelluloses for the Synthesis of Highly Stretchable, Tough, and Water-Resistant Co-continuous Filaments via Wet-Spinning}, volume={10}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.8b17790}, abstractNote={Heterogeneous acetylation of wood fibers is proposed for weakening their interfibrillar hydrogen bonding, which facilitates their processing into micro- and nanocelluloses that can be further used to synthesize filaments via wet-spinning. The structural (SEM, WAXD), molecular (SEC), and chemical (FTIR, titration) properties of the system are used to propose the associated reaction mechanism. Unlike the homogeneous acetylation, this method does not alter the main morphological features of cellulose fibrils. Thus, we show for the first time, the exploitation of synergies of compositions simultaneously comprising dissolved cellulose esters and suspended cellulose micro- and nanofibrils. Such colloidal suspension forms a co-continuous assembly with a matrix that interacts strongly with the micro- and nanofibrils in the dispersed phase. This facilitates uninterrupted and defect-free wet-spinning. Upon contact with an antisolvent (water), filaments are easily formed and display a set of properties that set them apart from those reported so far for nanocelluloses: a remarkable stretchability (30% strain) and ultrahigh toughness (33 MJ/m3), both surpassing the values of all reported nanocellulose-based filaments. All the while, they also exhibit competitive stiffness and strength (6 GPa and 143 MPa, respectively). Most remarkably, they retain 90% of these properties after long-term immersion in water, solving the main challenge of the lack of wet strength that is otherwise observed for filaments synthesized from nanocelluloses.}, number={51}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Tripathi, Anurodh and Ago, Mariko and Khan, Saad A. and Rojas, Orlando J.}, year={2018}, month={Dec}, pages={44776–44786} }
 @article{khakalo_filpponen_rojas_2018, title={Protein-mediated interfacial adhesion in composites of cellulose nanofibrils and polylactide: Enhanced toughness towards material development}, volume={160}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2018.03.013}, abstractNote={The role of animal protein, casein, as compatibilizer and eco-friendly dispersant in composites comprising cellulose nanofibrils (CNF) and polylactic acid (PLA) was investigated. The effect of casein-mediated surface modification of PLA was validated with dynamic adhesion experiments that considered the contact area according to JKR approximation. In fact, a remarkable increase by ∼50% in the work of adhesion between CNF and PLA was observed after casein adsorption. It is likely that the improved adhesion gave rise to an enhanced dispersion of CNF and PLA within the composite matrix. Moreover, the mechanical properties of the respective nanocomposites were significantly improved. When compared to protein-free CNF/PLA nanocomposites, the systems containing casein indicated an enhanced extensibility (by 130%) and tensile toughness (by 60%) whereas tensile strength and Young's modulus were improved to a limited extent (6 and 12%, respectively). Finally, it is demonstrated that the surface modification of PLA with casein improves the compatibility between CNF and PLA, which is a prerequisite for the feasible preparation of 3D shaped cellulose-based packaging materials by direct thermoforming.}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Khakalo, Alexey and Filpponen, Ilari and Rojas, Orlando J.}, year={2018}, month={May}, pages={145–151} }
 @article{eisa_abdelgawad_rojas_2018, title={Solid-State Synthesis of Metal Nanoparticles Supported on Cellulose Nanocrystals and Their Catalytic Activity}, volume={6}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.7b04333}, abstractNote={Heterogeneous catalysis has played a critical role in environmental remediation, for example, in processes that generate toxic streams. Thus, there is an ever-increasing need for green, cost-effective routes to synthesize highly active catalysts. In this study, a cellulose nanomaterial (cellulose nanocrystals, CNC) was employed as solid support for the nucleation of silver and gold nanoparticles via solid-state synthesis. The process involved solvent-free reduction in ambient conditions of metal precursors on the surface of CNC and in the presence of ascorbic acid. Surface plasmon resonance and X-ray diffraction indicated the successful formation of the metal nanoparticles, in the form of organic–inorganic hybrids. A strong hydrogen bonding was observed between CNC and the metal nanoparticles owing to the high density of hydroxyl groups in CNC, as determined by Fourier transform infrared spectroscopy. Electron microscopies indicated that the silver and gold precursors formed nanoparticles of hexagonal and...}, number={3}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Eisa, Wael H. and Abdelgawad, Abdelrahman M. and Rojas, Orlando J.}, year={2018}, month={Mar}, pages={3974–3983} }
 @article{tripathi_parsons_khan_rojas_2018, title={Synthesis of organic aerogels with tailorable morphology and strength by controlled solvent swelling following Hansen solubility}, volume={8}, ISSN={["2045-2322"]}, url={https://doi.org/10.1038/s41598-018-19720-4}, DOI={10.1038/s41598-018-19720-4}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Tripathi, Anurodh and Parsons, Gregory N. and Khan, Saad A. and Rojas, Orlando J.}, year={2018}, month={Feb} }
 @article{li_xie_wilt_willoughby_rojas_2018, title={Thermally Stable and Tough Coatings and Films Using Vinyl Silylated Lignin}, volume={6}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.7b03387}, abstractNote={We modified lignin, a renewable biomacromolecule with high carbon density, with silicon-containing vinyl groups via a highly efficient silylation reaction that achieved ∼30% substitution of lignin’s hydroxyl units. This exothermic process was carried out in the melt state, in situ, in a reactive extruder. 1H, 13C, and 31P NMR and FTIR confirmed the success of the silylation and were used to access the reactivity of the vinyl silylated lignin for copolymerization with polyacrylonitrile (PAN). Copolymers of the unmodified lignin and PAN were also produced as a reference. Importantly, the rheological behaviors of the copolymers of lignin and PAN were suitable for application in surface coating and films that were not possible if lignin or physical mixtures of lignin and PAN were used. Glass surfaces were treated via solution casting followed by oven drying, yielding films that were evaluated regarding their morphology (SEM) and thermal properties (TGA and DSC). The films produced with copolymers based on vin...}, number={2}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Li, Shuai and Xie, Wenyi and Wilt, Meghan and Willoughby, Julie A. and Rojas, Orlando J.}, year={2018}, month={Feb}, pages={1988–1998} }
 @article{abdelgawad_el-naggar_eisa_rojas_2017, title={Clean and high-throughput production of silver nanoparticles mediated by soy protein via solid state synthesis}, volume={144}, ISSN={["1879-1786"]}, DOI={10.1016/j.jclepro.2016.12.122}, abstractNote={A one-pot method that uses solid-state reactions at ambient temperature is proposed for high throughput and green synthesis of silver nanoparticles. Nano-sized silver metal was synthesized in less than 5 min by simply eco-grinding silver nitrate, soy protein isolate powder and sodium hydroxide pellets, in the absence of any solvent or organic protector. The loading and reduction efficiency of the reaction was readily controlled by adjusting the soy protein isolate/silver nitrate molar ratio and sodium hydroxide loading. The formation of nanostructured silver was elucidated by using complementary spectroscopy and imaging techniques, including ultra-violet spectroscopy, Transmission and Field Emission Scanning Electron microscopy with Energy Dispersive X-ray, Dynamic Light Scattering, X-Ray Diffraction, Fourier Transform infra-red spectroscopy and Surface Chemical Composition. The reducing effect of soy protein isolate to convert silver ions into silver nanoparticles in high yields was demonstrated, with no evidence of aggregation or phase separation. The results indicate excellent prospects toward cleaner and scale-up synthesis of silver nanoparticles.}, journal={JOURNAL OF CLEANER PRODUCTION}, author={Abdelgawad, Abdelrahman M. and El-Naggar, Mehrez E. and Eisa, Wael H. and Rojas, Orlando J.}, year={2017}, month={Feb}, pages={501–510} }
 @article{guo_filpponen_johansson_mohammadi_latikka_linder_ras_rojas_2017, title={Complexes of Magnetic Nanoparticles with Cellulose Nanocrystals as Regenerable, Highly Efficient, and Selective Platform for Protein Separation}, volume={18}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.6b01778}, abstractNote={We present an efficient approach to develop cellulose nanocrystal (CNC) hybrids with magnetically responsive Fe3O4 nanoparticles that were synthesized using the (Fe3+/Fe2+) coprecipitation. After 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-catalyzed oxidation of CNC, carbodiimide (EDC/NHS) was used for coupling amine-containing iron oxide nanoparticles that were achieved by dopamine ligand exchange (NH2-Fe3O4 NPs). The as-prepared hybrids (Fe3O4@CNC) were further complexed with Cu(II) ions to produce specific protein binding sites. The performance of magnetically responsive Cu-Fe3O4@CNC hybrids was assessed by selectively separating lysozyme from aqueous media. The hybrid system displayed a remarkable binding capacity with lysozyme of 860.6 ± 14.6 mg/g while near full protein recovery (∼98%) was achieved by simple elution. Moreover, the regeneration of Fe3O4@CNC hybrids and efficient reutilization for protein separation was demonstrated. Finally, lysozyme separation from matrices containing egg white was achieved, thus revealing the specificity and potential of the presented method.}, number={3}, journal={BIOMACROMOLECULES}, author={Guo, Jiaqi and Filpponen, Ilari and Johansson, Leena-Sisko and Mohammadi, Pezhman and Latikka, Mika and Linder, Markus B. and Ras, Robin H. A. and Rojas, Orlando J.}, year={2017}, month={Mar}, pages={898–905} }
 @article{el-naggar_abdelgawad_tripathi_rojas_2017, title={Curdlan cryogels reinforced with cellulose nanofibrils for controlled release}, volume={5}, ISSN={["2213-3437"]}, DOI={10.1016/j.jece.2017.10.056}, abstractNote={Curdlan based cryogels were prepared and tested for their structural and thermal properties by using field emission scanning electron microscopy and thermogravimetric analysis, respectively. Volume shrinkage, mechanical performance, swelling, solubility and density were accessed as a function of composition, which included cellulose nanofibrils (CNF) and polyethylene oxide (PEO). PEO/CURD and PEO/CURD/CNF cryogels exhibited porous and layered structures. The addition of CNF significantly improved the in-vitro release of a nonsteroidal anti-inflammatory drug (diclofenac sodium), which is a promising alternative to current non-biodegradable systems.}, number={6}, journal={JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING}, author={El-Naggar, Mehrez E. and Abdelgawad, Abdelrahman M. and Tripathi, Anurodh and Rojas, Orlando J.}, year={2017}, month={Dec}, pages={5754–5761} }
 @article{tayeb_hubbe_zhang_rojas_2017, title={Effect of Lipoxygenase Oxidation on Surface Deposition of Unsaturated Fatty Acids}, volume={33}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.7b00908}, abstractNote={We studied the interactions of lipid molecules (linoleic acid, glycerol trilinoleate and a complex mixture of wood extractives) with hydrophilic and hydrophobic surfaces (cellulose nanofibrils (CNFs) and polyethylene terephthalate (PET), respectively). The effect of lipoxygenase treatment to minimize the affinity of the lipids with the given surface was considered. Application of an electroacoustic sensing technique (QCM) allowed the monitoring of the kinetics of oxidation as well as dynamics of lipid deposition on CNF and PET. The effect of the lipoxygenase enzymes (LOX) was elucidated with regards to their ability to reduce the formation of soiling lipid layers. The results pointed to the fact that the rate of colloidal oxidation depended on the type of lipid substrate. The pretreatment of the lipids with LOX reduced substantially their affinity to the surfaces, especially PET. Surface plasmon resonance (SPR) sensograms confirmed the effect of oxidation in decreasing the extent of deposition on the hydrophilic CNF. QCM energy dissipation analyses revealed the possible presence of a loosely adsorbed lipid layer on the PET surface. The morphology of the deposits accumulated on the solids was determined by atomic force microscopy and indicated important changes upon lipid treatment with LOX. The results highlighted the benefit of enzyme as a biobased treatment to reduce hydrophobic interactions, thus providing a viable solution to the control of lipid deposition from aqueous media.}, number={18}, journal={LANGMUIR}, author={Tayeb, Ali H. and Hubbe, Martin A. and Zhang, Yanxia and Rojas, Orlando J. u}, year={2017}, month={May}, pages={4559–4566} }
 @article{abdelgawad_el-naggar_hudson_rojas_2017, title={Fabrication and characterization of bactericidal thiol-chitosan and chitosan iodoacetamide nanofibres}, volume={94}, ISSN={["1879-0003"]}, DOI={10.1016/j.ijbiomac.2016.07.061}, abstractNote={Two chitosan derivatives, namely, thiol-chitosan (TCs) and chitosan iodoacetamide (CsIA) were newly synthesized by reacting Cs with thiglycolic acid (TGA) and iodoacetic acid (IA) respectively. After being crosslinked with glutraldehyde (GA), the two derivatives were submitted to FT-IR and H1 NMR analysis for identification and characterization of their chemical features. As TCs and CsIA are water soluble, their electrospun nanofibres mats from aqueous solutions could be crosslinked and achieved using polyvinyl alcohol/Chitosan blend (PVA/Cs) polymers. Morphological structures of the obtained nanofibres and their webs were studied via those of TCs and CsIA free systems. The data also indicate that the crosslinked PVA/Cs/CsIA is more thermally stable than the crosslinked PVA/Cs/TCs and crosslinked PVA/Cs respectively. It was proved that the electrospun fibers containing TCs or CsIA display a superior antibacterial activity against negative bacteria E. Coli with a minimum inhibitory concentration (MIC) of 400μg/ml. These effects are rather in confirmation with bacterial kinetics essays which were also carried out in current work. Of particular interest is that the antimicrobial properties of fibers containing small concentration of either TCs or CsIA are much superior than those obtained with neat Cs electrospun nanofibres used as reference. By and large the results advocate the fibers webs containing TCs or CsIA as excellent candidates for wound dressing applications.}, journal={INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES}, author={Abdelgawad, Abdelrahman M. and El-Naggar, Mehrez E. and Hudson, Samuel M. and Rojas, Orlando J.}, year={2017}, month={Jan}, pages={96–105} }
 @article{vuoriluoto_orelma_lundahl_borghei_rojas_2017, title={Filaments with Affinity Binding and Wet Strength Can Be Achieved by Spinning Bifunctional Cellulose Nanofibrils}, volume={18}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.7b00256}, abstractNote={We demonstrate benzophenone (BP) conjugation via amine-reactive esters onto oxidized cellulosic fibers that were used as precursors, after microfluidization, of photoactive cellulose nanofibrils (CNF). From these fibrils, cellulose I filaments were synthesized by hydrogel spinning in an antisolvent followed by fast biradical UV cross-linking. As a result, the wet BP-CNF filaments retained extensively the original dry strength (a remarkable ∼80% retention). Thus, the principal limitation of these emerging materials was overcome (the wet tensile strength is typically <0.5% of the value measured in dry conditions). Subsequently, antihuman hemoglobin (anti-Hb) antibodies were conjugated onto residual surface carboxyl groups, making the filaments bifunctional for their active groups and properties (wet strength and bioactivity). Optical (surface plasmon resonance) and electroacoustic (quartz crystal microgravimetry) measurements conducted with the bifunctional CNF indicated effective anti-Hb conjugation (2.4 mg m-2), endowing an excellent sensitivity toward Hb targets (1.7 ± 0.12 mg m-2) and negligible nonspecific binding. Thus, the anti-Hb biointerface was deployed on filaments that captured Hb efficiently from aqueous matrices (confocal laser microscopy of FITC-labeled antibodies). Significantly, the anti-Hb biointerface was suitable for regeneration, while its sensitivity and selectivity in affinity binding can be tailored by application of blocking copolymers. The developed bifunctional filaments based on nanocellulose offer great promise in detection and affinity binding built upon 1D systems, which can be engineered into other structures for rational use of material and space.}, number={6}, journal={BIOMACROMOLECULES}, author={Vuoriluoto, Maija and Orelma, Hannes and Lundahl, Meri and Borghei, Maryam and Rojas, Orlando J.}, year={2017}, month={Jun}, pages={1803–1813} }
 @article{zhang_rojas_2017, title={Immunosensors for C-Reactive Protein Based on Ultrathin Films of Carboxylated Cellulose Nanofibrils}, volume={18}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.6b01681}, abstractNote={C-reactive protein (CRP) is an acute phase protein that has been widely used as a predictor of cardiovascular diseases. We report herein the synthesis of immunosensors based on carboxylated cellulose nanofibrils (CNF) for CRP detection, as demonstrated by quartz crystal microgravimetry (QCM). QCM sensors carrying ultrathin films of carboxylated CNF were prepared by using two protocols: (i) spin coating of CNF on the sensors followed by carboxylation via in situ oxidation with 2,2,6,6-tetramethylpiperidine 1-oxyl and (ii) carboxymethylation of CNF in aqueous dispersion followed by spin coating deposition on the sensors. Protein A was conjugated to the carboxylated CNF via N-(3-(Dimethylamino)propyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide and used as a ligand for oriented immobilization of anti C-reactive protein (anti-CRP). The different carboxyl group density of the two oxidized CNF surfaces influenced Protein A binding and, subsequently, the available immobilized anti-CRP molecules. The detection efficiency for CRP, specificity, and concentration range displayed by the carboxylated CNF-based immunosensors coupled with oriented and unoriented anti-CRP were determined and compared.}, number={2}, journal={BIOMACROMOLECULES}, author={Zhang, Yanxia and Rojas, Orlando J.}, year={2017}, month={Feb}, pages={526–534} }
 @article{khakalo_kouko_filpponen_retulainen_rojas_2017, title={In-Plane Compression and Biopolymer Permeation Enable Super-stretchable Fiber Webs for Thermoforming toward 3-D Structures}, volume={5}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.7b02025}, abstractNote={The typically poor ductility of cellulosic fibers and ensuing bonded networks and paper webs set limits on any effort to produce associated three-dimensional structures without relying on chemical, often unsustainable, approaches. To address this challenge, we report on a facile and green method that combines mechanical and biopolymer treatment: in-plane compression and aqueous solution permeation via spraying. The first enabled network extensibility while the second, which relied on the use of either food-grade gelatin, guar gum, or polylactic acid, improved network strength and stiffness. As a result, an unprecedented elongation of ∼30% was achieved after unrestrained drying of the fiber web. At the same time, the structures experienced a significant increase in tensile strength and stiffness (by ∼306% and ∼690%, respectively). Such simultaneous property improvement, otherwise very difficult to achieve, represents a substantial gain in the material’s toughness, which results from the synergistic effects...}, number={10}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Khakalo, Alexey and Kouko, Jarmo and Filpponen, Ilari and Retulainen, Elias and Rojas, Orlando J.}, year={2017}, month={Oct}, pages={9114–9125} }
 @article{pereira_hoeger_ferrer_rencoret_rio_kruus_rahikainen_kellock_gutierrez_rojas_2017, title={Lignin Films from Spruce, Eucalyptus, and Wheat Straw Studied with Electroacoustic and Optical Sensors: Effect of Composition and Electrostatic Screening on Enzyme Binding}, volume={18}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.7b00071}, abstractNote={Lignins were isolated from spruce, wheat straw, and eucalyptus by using the milled wood lignin (MWL) method. Functional groups and compositional analyses were assessed via 2D NMR and 31P NMR to realize their effect on enzyme binding. Films of the lignins were fabricated and ellipsometry, atomic force microscopy, and water contact angle measurements were used for their characterization and to reveal the changes upon enzyme adsorption. Moreover, lignin thin films were deposited on quartz crystal microgravimetry (QCM) and surface plasmon (SPR) resonance sensors and used to gain further insights into the lignin-cellulase interactions. For this purpose, a commercial multicomponent enzyme system and a monocomponent Trichoderma reesei exoglucanase (CBH-I) were considered. Strong enzyme adsorption was observed on the various lignins but compared to the multicomponent cellulases, CBH-I displayed lower surface affinity and higher binding reversibility. This resolved prevalent questions related to the affinity of this enzyme with lignin. Remarkably, a strong correlation between enzyme binding and the syringyl/guaiacyl (S/G) ratio was found for the lignins, which presented a similar hydroxyl group content (31P NMR): higher protein affinity was determined on isolated spruce lignin (99% G units), while the lowest adsorption occurred on isolated eucalyptus lignin (70% S units). The effect of electrostatic interactions in enzyme adsorption was investigated by SPR, which clearly indicated that the screening of charges allowed more extensive protein adsorption. Overall, this work furthers our understanding of lignin-cellulase interactions relevant to biomass that has been subjected to no or little pretreatment and highlights the widely contrasting effects of the nature of lignin, which gives guidance to improve lignocellulosic saccharification and related processes.}, number={4}, journal={BIOMACROMOLECULES}, author={Pereira, Antonio and Hoeger, Ingrid C. and Ferrer, Ana and Rencoret, Jorge and Rio, Jose C. and Kruus, Kristiina and Rahikainen, Jenni and Kellock, Miriam and Gutierrez, Ana and Rojas, Orlando J.}, year={2017}, month={Apr}, pages={1322–1332} }
 @article{tayeb_sadeghifar_hubbe_rojas_2017, title={Lipoxygenase-mediated peroxidation of model plant extractives}, volume={104}, ISSN={["1872-633X"]}, DOI={10.1016/j.indcrop.2017.04.041}, abstractNote={Three unsaturated fatty acids, namely 9-cis,12-cis-linoleic acid, 1,2,3-tri-cis, cis-9,12-octadecadienoyl (glycerol trilinolein) and 1,2,3-tri-cis-9-octadecenoyl (triolein) were selected as models of components of plant extractives to monitor the hydroperoxygenation induced by soybean lipoxygenase (LOX), which was applied as an oxidative catalyst at room temperature. The fatty acids were monitored in colloidal dispersions in relation to their molecular changes using 1H/13C nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and UV spectroscopies. The detection of the hydroperoxy group was limited due to its unstable nature. However, the reduction of protons associated with the diene groups and the substitution of hydroperoxy groups at the allylic positon in conjugated lipids were detected by the induced chemical shift of HOO-bearing 13C and 1H resonances and the oxygen absorption owing to changes in the molecule. Moreover, compared to the two other substrates, no oxygen substitution was observed in triolein, in accordance with its lower level of saturation and the absence of bis-allylic carbon. Our results are of relevance to plant fiber processing, since fatty acids are major constituents of hydrophobic deposits that cause a range of manufacturing challenges.}, journal={INDUSTRIAL CROPS AND PRODUCTS}, author={Tayeb, Ali H. and Sadeghifar, Hasan and Hubbe, Martin A. and Rojas, Orlando J.}, year={2017}, month={Oct}, pages={253–262} }
 @misc{hubbe_ferrer_tyagi_yin_salas_pal_rojas_2017, title={Nanocellulose in thin films, coatings, and plies for packaging applications: a review}, volume={12}, number={1}, journal={BioResources}, author={Hubbe, M. A. and Ferrer, A. and Tyagi, P. and Yin, Y. Y. and Salas, C. and Pal, L. and Rojas, O. J.}, year={2017}, pages={2143–2233} }
 @misc{tardy_yokota_ago_xiang_kondo_bordes_rojas_2017, title={Nanocellulose-surfactant interactions}, volume={29}, DOI={10.1016/j.cocis.2017.02.004}, abstractNote={Biomass-derived nanomaterials, such as cellulose nanocrystals and nanofibrils, are attractive building blocks for the formulation of foams, emulsions, suspensions and multiphase systems. Depending on their surface chemistry, aspect ratio and crystallinity, nanocelluloses can control the rheology and stability of dispersions; they can also confer robust mechanical properties to composites. Synthetic modification of fibrillar cellulose is an option to achieve chemical compatibility in related systems, in the formation of composites, etc. However, this can also limit the environmental benefits gained from the use of the cellulosic component. Thus, an attractive mean to compatibilize and to further expand the applications of nanocelluloses is through the use of surfactants. The chemical toolbox of surfactants developed over the last 60 years allows for a large versatility while their environmental impact can also be minimized. Furthermore, relatively small amounts of surfactants are sufficient to significantly impact the interfacial forces, which has implications in material development, from the colloidal scale to the macro-scale. In this review we attempt to cover the literature pertaining to the combined uses of surfactants and nanocelluloses. We summarize reports on the incorporation with nanocellulose of nonionic, anionic, amphoteric and cationic surfactants. With the ever-expanding interest in the use of renewable materials in a vast range of applications, we hope to provide insights into the application of surfactants as a tool to tailor the compatibility and the surface chemistry of nanocelluloses.}, journal={Current Opinion in Colloid & Interface Science}, author={Tardy, B. L. and Yokota, S. and Ago, M. and Xiang, W. C. and Kondo, T. and Bordes, R. and Rojas, O. J.}, year={2017}, pages={57–67} }
 @article{guo_liu_filpponen_johanson_malho_quraishi_liebner_santos_rojas_2017, title={Photoluminescent Hybrids of Cellulose Nanocrystals and Carbon Quantum Dots as Cytocompatible Probes for in Vitro Bioimaging}, volume={18}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.7b00306}, abstractNote={We present an approach to construct biocompatible and photoluminescent hybrid materials comprised of carbon quantum dots (CQDs) and TEMPO-oxidized cellulose nanocrystals (TO-CNCs). First, the amino-functionalized carbon quantum dots (NH2-CQDs) were synthesized using a simple microwave method, and the TO-CNCs were prepared by hydrochloric acid (HCl) hydrolysis followed by TEMPO-mediated oxidation. The conjugation of NH2-CQDs and TO-CNCs was conducted via carbodiimide-assisted coupling chemistry. The synthesized TO-CNC@CQD hybrid nanomaterials were characterized using X-ray photoelectron spectroscopy, cryo-transmittance electron microscopy, confocal microscopy, and fluorescence spectroscopy. Finally, the interactions of TO-CNC@CQD hybrids with HeLa and RAW 264.7 macrophage cells were investigated in vitro. Cell viability tests suggest the surface conjugation with NH2-CQDs not only improved the cytocompatibility of TO-CNCs, but also enhanced their cellular association and internalization on both HeLa and RAW 264.7 cells after 4 and 24 h incubation.}, number={7}, journal={BIOMACROMOLECULES}, author={Guo, Jiaqi and Liu, Dongfei and Filpponen, Ilari and Johanson, Leena-Sisko and Malho, Jani-Markus and Quraishi, Sakeena and Liebner, Falk and Santos, Helder A. and Rojas, Orlando J.}, year={2017}, month={Jul}, pages={2045–2055} }
 @article{khakalo_filpponen_rojas_2017, title={Protein Adsorption Tailors the Surface Energies and Compatibility between Polylactide and Cellulose Nanofibrils}, volume={18}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.7b00173}, abstractNote={The state of dispersion and the interactions between a polymer and a filler in a nanocomposite crucially define its properties and performance. The affinity of polylactide (PLA) with vegetable and animal proteins (casein, gelatin, soy protein isolate, and hydrolysate) is investigated and their role as eco-friendly dispersants and compatibilizers of cellulose nanofibrils (CNF) is elucidated. The affinity of the proteins with PLA is determined by using sensograms acquired by electroacoustic (quartz crystal microgravimetry) and optical (surface plasmon resonance) techniques. The surface energy of PLA increases upon protein adsorption while the opposite effect is observed for CNF, under identical experimental conditions. A significant improvement in the thermodynamic work of adhesion for PLA/CNF systems is predicted by application of the denatured proteins at low concentrations (∼20% and ∼15% enhancement with soy protein and casein at pH 3 and pH 8, respectively). We offer a robust method to screen denatured proteins and to tailor the wettability and material compatibility in the synthesis of bionanocomposites based on CNF and PLA.}, number={4}, journal={BIOMACROMOLECULES}, author={Khakalo, Alexey and Filpponen, Ilari and Rojas, Orlando J.}, year={2017}, month={Apr}, pages={1426–1433} }
 @article{fritz_salas_jameel_rojas_2017, title={Self-association and aggregation of kraft lignins via electrolyte and nonionic surfactant regulation: stabilization of lignin particles and effects on filtration}, volume={32}, number={4}, journal={Nordic Pulp & Paper Research Journal}, author={Fritz, C. and Salas, C. and Jameel, H. and Rojas, O. J.}, year={2017}, pages={572–585} }
 @article{tayeb_hubbe_tayeb_pal_rojas_2017, title={Soy Proteins As a Sustainable Solution to Strengthen Recycled Paper and Reduce Deposition of Hydrophobic Contaminants in Papermaking: A Bench and Pilot-Plant Study}, volume={5}, ISSN={2168-0485 2168-0485}, url={http://dx.doi.org/10.1021/acssuschemeng.7b01425}, DOI={10.1021/acssuschemeng.7b01425}, abstractNote={Hydrophobic contaminants (stickies) incorporated with recycled fibers cause severe papermaking processing and product quality problems, which lead to low runnability and increased production cost. Stickies negatively affect paper strength and many other properties. In this work, we propose a sustainable approach by the application of soy protein isolate (SPI), soy flour (SF), and soybean lipoxygenase (LOX) as agents to combat hydrophobic contaminants. Tests at the bench and pilot-plant scales and under conditions similar to industrial operations demonstrated the reduction of associated challenges and the improvement of a paper’s dry strength. The soy agents were applied to aqueous dispersions of lignin-free recycled fibers (dosage levels of 1–2% based on the fiber dry weight), which contained additives typically used in papermaking (fillers, sizing agent, and others). Talc, a common detackifier, was applied in similar systems that were used as reference. The proteins were added under both high and low she...}, number={8}, journal={ACS Sustainable Chemistry & Engineering}, publisher={American Chemical Society (ACS)}, author={Tayeb, Ali H. and Hubbe, Martin A. and Tayeb, Pegah and Pal, Lokendra and Rojas, Orlando J.}, year={2017}, month={Jul}, pages={7211–7219} }
 @article{shen_rojas_genzer_gurgel_carbonell_2016, title={Affinity interactions of human immunoglobulin G with short peptides: role of ligand spacer on binding, kinetics, and mass transfer}, volume={408}, ISSN={["1618-2650"]}, DOI={10.1007/s00216-015-9135-y}, abstractNote={The interaction affinity between human IgG and a short peptide ligand (hexameric HWRGWV) was investigated by following the shifts in frequency and energy dissipation in a quartz crystal microbalance (QCM). HWRGWV was immobilized by means of poly(ethylene glycol) tethered on QCM sensors coated with silicon oxide, which enhanced the accessibility of the peptide to hIgG and also passivated the surface. Ellipsometry and ToF-SIMS were employed for surface characterization. The peptide ligand density was optimized to 0.88 chains nm(-2), which enabled the interaction of each hIgG molecule with at least one ligand. The maximum binding capacity was found to be 4.6 mg m(-2), corresponding to a monolayer of hIgG, similar to the values for chromatographic resins. Dissociation constants were lower than those obtained from resins, possibly due to overestimation of bound mass by QCM. Equilibrium thermodynamic and kinetic parameters were determined, shedding light on interfacial effects important for detection and bioseparation. Graphical Abstract The interaction affinity between human IgG and a short peptide ligand was investigated by using quartz crystal microgravimetry, ellipsometry and ToF-SIMS. Equilibrium thermodynamic and kinetics parameters were determined, shedding light on interfacial effects important for detection and bioseparation.}, number={7}, journal={ANALYTICAL AND BIOANALYTICAL CHEMISTRY}, author={Shen, Fei and Rojas, Orlando J. and Genzer, Jan and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2016}, month={Mar}, pages={1829–1841} }
 @article{yan_abdelgawad_el-naggar_rojas_2016, title={Antibacterial activity of silver nanoparticles synthesized In-situ by solution spraying onto cellulose}, volume={147}, ISSN={["1879-1344"]}, DOI={10.1016/j.carbpol.2016.03.029}, abstractNote={Spray technique was used for the adsorption of in-situ silver nanoparticles (AgNPs) onto and inside the surface of nano- and micro- fibrillar cellulose (NFC and MFC) as well as filter paper. The abundance of hydroxyl and carboxyl groups located in NFC and MFC are used to stabilize Ag ions (Ag+) which were then in-situ reduced to (AgNPs) by chemical or UV reduction. The surface characteristic features, elemental analysis, particle size as well as size distribution of the obtained MFC, NFC and filter paper loaded with AgNPs were characterized via field emission scanning electron microscopy connected to energy dispersive X-ray spectroscopy (FESEM- EDX) and transmission electron microscopy (TEM). The associated chemical changes after growth of AgNPs onto the cellulose substrates were assessed by fourier transform infra-red (FT-IR) while the thermal stability of such systems were investigated by thermogravimetrical analyses (TGA). The antibacterial properties of AgNPs loaded NFC, MFC and filter paper as well was investigated against Escherichia Coli. The resulted data indicate that the particle size was found to be 11 and 26 nm for AgNPs nucleated on NFC and MFC—based papers respectively. The antibacterial activity of AgNPs loaded MFC exhibited higher antibacterial activity than that of AgNPs loaded NFC. Overall, the present research demonstrates facile and fast method for in-situ antibacterial AgNPs loading on cellulose substrates.}, journal={CARBOHYDRATE POLYMERS}, author={Yan, Jinhua and Abdelgawad, Abdelrahman M. and El-Naggar, Mehrez E. and Rojas, Orlando J.}, year={2016}, month={Aug}, pages={500–508} }
 @article{ye_li_lu_zhang_rojas_2016, title={Antioxidant and Thermal Stabilization of Polypropylene by Addition of Butylated Lignin at Low Loadings}, volume={4}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.6b01241}, abstractNote={The effect of phenolic hydroxyl group content and molecular mass of a technical lignin on the thermo-oxidation resistance and compatibility with polypropylene (PP) was studied by a combination of approaches, including 31P NMR, gel permeation chromatography (GPC), thermogravimetry (TG), dynamic scanning calorimetry (DSC), accelerated aging tests, scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA). The compatibility of lignin with PP upon melt compounding in a screw system was improved after modification of lignin with n-butyric anhydride. The thermal oxidation stability of films of PP blends, as measured in an oxygen atmosphere, was increased by low addition levels of the butylated lignins while maintaining, and in some cases improving, their thermo-mechanical performance. Notably, the oxidation induction time (OIT) and induction aging time of PP blended with butylated lignins (<5% loadings) reached maximum values of 16 min and 576 h, respectively, indicating an effect equivalent to ...}, number={10}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Ye, Dezhan and Li, Shuai and Lu, Xiaomin and Zhang, Xi and Rojas, Orlando J.}, year={2016}, month={Oct}, pages={5248–5257} }
 @article{guo_filpponen_su_laine_rojas_2016, title={Attachment of gold nanoparticles on cellulose nanofibrils via click reactions and electrostatic interactions}, volume={23}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-016-1042-7}, number={5}, journal={CELLULOSE}, author={Guo, Jiaqi and Filpponen, Ilari and Su, Pingping and Laine, Janne and Rojas, Orlando J.}, year={2016}, month={Oct}, pages={3065–3075} }
 @article{mattos_rojas_magalhaes_2016, title={Biogenic SiO2 in colloidal dispersions via ball milling and ultrasonication}, volume={301}, ISSN={["1873-328X"]}, DOI={10.1016/j.powtec.2016.05.052}, abstractNote={Biogenic silica from Equisetum arvense was dispersed in aqueous media by using ball milling, high-energy planetary ball milling and ultrasonication. Zeta potential (ζ), dynamic light scattering, and transmission electron microscopy revealed the electrostatic charge and morphological characteristics of the particles, which formed stable colloidal dispersions. Ball milling and ultrasonication yielded particles of 10 nm in size that clustered into larger structures. Extended milling time was effective in reducing the particle size by ball milling and ultrasonication but not by high-energy planetary ball milling. The colloidal stability of the dispersions was maximized under alkaline conditions (ζ > − 30 mV and smallest cluster size of 100–200 nm).}, journal={POWDER TECHNOLOGY}, author={Mattos, Bruno D. and Rojas, Orlando J. and Magalhaes, Washington L. E.}, year={2016}, month={Nov}, pages={58–64} }
 @article{li_ogunkoya_fang_willoughby_rojas_2016, title={Carboxymethylated lignins with low surface tension toward low viscosity and highly stable emulsions of crude bitumen and refined oils}, volume={482}, ISSN={["1095-7103"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84979781362&partnerID=MN8TOARS}, DOI={10.1016/j.jcis.2016.07.063}, abstractNote={Kraft and organosolv lignins were subjected to carboxymethylation to produce fractions that were soluble in water, displayed a minimum surface tension as low as 34mN/m (25°C) and a critical aggregation concentration of ∼1.5wt%. The carboxymethylated lignins (CML), which were characterized in terms of their degree of substitution ((31)P NMR), elemental composition, and molecular weight (GPC), were found suitable in the formulation of emulsions with bitumens of ultra-high viscosity, such as those from the Canadian oil sands. Remarkably, the interfacial features of the CML enabled fuel emulsions that were synthesized in a very broad range of internal phase content (30-70%). Cryo-replica transmission electron microscopy, which was used here the first time to assess the morphology of the lignin-based emulsions, revealed the droplets of the emulsion stabilized with the modified lignin. The observed drop size (diameters<2μm) was confirmed by light scattering, which revealed a normal size distribution. Such characteristics led to stable emulsified systems that are amenable for a wide range of applications. Emulsification with CML afforded bitumen emulsions with very high colloidal stability (no change was noted for over one month) and with a strong shear thinning behavior. Both features indicate excellent prospects for storage, transport and spraying, which are relevant in operations for power generation, which also take advantage of the high heating value of the emulsion components. The ability of CML to stabilize emulsions and to contribute in their combustion was tested with light fuels (kerosene, diesel, and jet fuel) after formulation of high internal phase systems (70% oil) that enabled operation of a fuel engine. A significant finding is that under certain conditions and compared to the respective pure fuel, combustion of the O/W emulsions stabilized by CML presented lower NOx and CO emissions and maintained a relatively high combustion efficiency. The results highlight the possibilities in high volume application for lignin biomacromolecules.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Li, Shuai and Ogunkoya, Dolanimi and Fang, Tiegang and Willoughby, Julie and Rojas, Orlando J.}, year={2016}, month={Nov}, pages={27–38} }
 @article{el-naggar_abdelgawad_salas_rojas_2016, title={Curdlan in fibers as carriers of tetracycline hydrochloride: Controlled release and antibacterial activity}, volume={154}, ISSN={["1879-1344"]}, DOI={10.1016/j.carbpol.2016.08.042}, abstractNote={Curdlan (CURD) and polyethylene oxide were used to synthesize nanofibers as carriers of hydro soluble tetracycline hydrochloride (TCH). The viscosity, surface tension and conductivity of the precursor multicomponent aqueous solutions were determined and adjusted to produce defect-free fiber webs. Except for a slight increase in diameter, the addition of TCH did not affect the original morphology of the CURD/PEO nanofibers, as determined by FE-SEM imaging. However, the thermal stability of the system was enhanced (TGA and DSC). Moreover, water resistance, as measured with 24-h immersion tests, was observed upon crosslinking with glutaraldehyde. In-vitro activity measurements indicated a sustained and controlled TCH time-release pattern and excellent antibacterial activity against E. coli, as assessed by UV-vis spectroscopy and viable cell counting, respectively. Overall, we propose nanofibers based on CURD as promising platforms for scaffolds for wound dressing and drug delivery.}, journal={CARBOHYDRATE POLYMERS}, author={El-Naggar, Mehrez E. and Abdelgawad, Abdelrahman M. and Salas, Carlos and Rojas, Orlando J.}, year={2016}, month={Dec}, pages={194–203} }
 @article{carrillo_nypeloe_rojas_2016, title={Double emulsions for the compatibilization of hydrophilic nanocellulose with non-polar polymers and validation in the synthesis of composite fibers}, volume={12}, ISSN={["1744-6848"]}, DOI={10.1039/c5sm02578h}, abstractNote={A route for the compatibilization of aqueous dispersions of cellulose nanofibrils (CNFs) with a non-polar polymer matrix is proposed to overcome a major challenge in CNF-based material synthesis. Non-ionic surfactants were used in CNF aqueous dispersions equilibrated with an organic phase (for demonstration, a polystyrene solution, PS, was used). Stable water-in-oil-in-water (W/O/W) double emulsions were produced as a result of the compromise between composition and formulation variables. Most remarkably, the proposed route for CNF integration with hydrophobic polymers removed the need for drying or solvent-exchange of the CNF aqueous dispersion prior to processing. The rheological behavior of the double emulsions showed strong shear thinning behavior and facilitated CNF-PS co-mixing in solid nanofibers upon electrospinning. The morphology and thermal properties of the resultant nanofibers revealed that CNFs were efficiently integrated in the hydrophobic matrix which was consistent with the high interfacial area of the precursor double emulsion. In addition, the morphology and quality of the composite nanofibers can be controlled by the conductivity (ionic strength) of the CNF dispersion. Overall, double emulsion systems are proposed as a novel, efficient and scalable platform for CNF co-processing with non-polar systems and they open up the possibility for the redispersion of CNFs after removal of the organic phase.}, number={10}, journal={SOFT MATTER}, author={Carrillo, Carlos A. and Nypeloe, Tiina and Rojas, Orlando J.}, year={2016}, pages={2721–2728} }
 @article{li_xiang_jarvinen_lappalainen_salminen_rojas_2016, title={Interfacial Stabilization of Fiber-Laden Foams with Carboxymethylated Lignin toward Strong Nonwoven Networks}, volume={8}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.6b06418}, abstractNote={Wet foams were produced via agitation and compressed air bubbling of aqueous solutions of carboxymethylated lignin (CML). Bubble size and distribution were assessed in situ via optical microscopy. Foamability, bubble collapse rate, and foam stability (half-life time) were analyzed as a function of CML concentration, temperature, pH, and air content. Dynamic changes of the CML liquid foam were monitored by light transmission and backscattering. Cellulosic fibers of different aspect ratios (long pine fibers and short birch fibers) were suspended under agitation by the liquid foams (0.6% CML in the aqueous phase) with an air (bubble) content as high as 75% in volume. Remarkably, the half-life time of fiber-laden CML foams was 10-fold higher than that of the corresponding fiber-free liquid foam. Such lignin-based foams were demonstrated, after dewatering, as a precursor for the synthesis of nonwoven, layered structures. The resulting fiber networks (paper), obtained here for the first time with lignin-based foams, were characterized for pore size distribution, lignin retention, morphology, and physical-mechanical properties (network formation quality, density, air permeability, surface roughness, and tensile and internal bond strengths). The results were compared against structures obtained from foams stabilized with an anionic surfactant (SDS) as well as those from foam-free, water-based web-laying. Remarkably, compared to SDS, the foam-formed materials produced with CML displayed better bonding and tensile strengths. Overall, CML-based foams were found to be suitable carriers of cellulosic fibers and have opened the possibility for integrating fully biobased systems in foam-forming. This is an emerging option to increase the effective solids content in the system without compromising the quality of formed nonwoven materials while achieving reductions in water and energy consumption.}, number={30}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Li, Shuai and Xiang, Wenchao and Jarvinen, Marjo and Lappalainen, Timo and Salminen, Kristian and Rojas, Orlando J.}, year={2016}, month={Aug}, pages={19827–19835} }
 @article{li_willoughby_rojas_2016, title={Oil-in-Water Emulsions Stabilized by Carboxymethylated Lignins: Properties and Energy Prospects}, volume={9}, ISSN={["1864-564X"]}, DOI={10.1002/cssc.201600704}, abstractNote={Abstract}, number={17}, journal={CHEMSUSCHEM}, author={Li, Shuai and Willoughby, Julie A. and Rojas, Orlando J.}, year={2016}, month={Sep}, pages={2460–2469} }
 @article{ferrer_salas_rojas_2016, title={Physical, thermal, chemical and rheological characterization of cellulosic microfibrils and microparticles produced from soybean hulls}, volume={84}, ISSN={["1872-633X"]}, DOI={10.1016/j.indcrop.2016.02.014}, abstractNote={Soybean hulls were used to isolate cellulosic microfibrils (SMF) and brick-like microparticles (SMP) by combining chemical and mechanical pretreatments. The key physical and chemical features of SMF and SMP were compared with those of micro and nanofibrillated cellulose (MNFC) obtained from fully bleached wood fibers. SMF and SMP chemical composition includes residual polysaccharides and lignin that endow such biologically-derived materials with properties typical of nanocellulosics. Compared to MNFC, SMF and SMP exhibit enhanced crystallinity (∼ > 10% higher) and thermal stability (onset degradation temperature >295 °C and maximum degradation at 361 and 355 °C). Such observations make SMF and SMP suitable for reinforcement in thermoplastic composites. A strong shear thinning behavior was observed for aqueous dispersions of SMF and SMP, revealing that these cellulose microstructures are of interest for rheology modification, coatings and films. Overall, the availability and low cost of biomass from residual soybean hulls constitutes a viable option for their use as a feedstock for the production and development of novel materials from SMF and SMP.}, journal={INDUSTRIAL CROPS AND PRODUCTS}, author={Ferrer, Ana and Salas, Carlos and Rojas, Orlando J.}, year={2016}, month={Jun}, pages={337–343} }
 @article{ferrer_hoeger_lu_rojas_2016, title={Reinforcement of polypropylene with lignocellulose nanofibrils and compatibilization with biobased polymers}, volume={133}, ISSN={["1097-4628"]}, DOI={10.1002/app.43854}, abstractNote={ABSTRACT}, number={34}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Ferrer, Ana and Hoeger, Ingrid C. and Lu, Xiaomin and Rojas, Orlando J.}, year={2016}, month={Sep} }
 @article{ago_ferrer_rojas_2016, title={Starch-Based Biofoams Reinforced with Lignocellulose Nanofibrils from Residual Palm Empty Fruit Bunches: Water Sorption and Mechanical Strength}, volume={4}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.6b01279}, abstractNote={Lignin-containing cellulosic nanofibrils (LCNF) were extracted from residual oil palm empty fruit bunches (EFB), an abundant but underutilized bioresource, by using a set of sulfur-free fractionation methods. The various types of isolated LCNF were used to reinforce starch-based biofoams. The incorporation of LCNF achieved remarkable increases, by a factor of 44 and 66, of the Young’s modulus and yield stress in compression mode, respectively. In addition, owing to the relatively lower hydrophilicity of residual lignin, water sorption by the composite biofoams was reduced with LCNF loading. The starch/LCNF nanocomposite biofoams displayed mechanical properties similar to those of polystyrene foams and therefore can potentially represent a sustainable and green alternative for packaging and insulation materials.}, number={10}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Ago, Mariko and Ferrer, Ana and Rojas, Orlando J.}, year={2016}, month={Oct}, pages={5546–5552} }
 @article{kamarainen_arcot_johansson_campbell_tammelin_franssila_laine_rojas_2016, title={UV-ozone patterning of micro-nano fibrillated cellulose (MNFC) with alkylsilane self-assembled monolayers}, volume={23}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-016-0942-x}, number={3}, journal={CELLULOSE}, author={Kamarainen, Tero and Arcot, Lokanathan R. and Johansson, Leena-Sisko and Campbell, Joseph and Tammelin, Tekla and Franssila, Sami and Laine, Janne and Rojas, Orlando J.}, year={2016}, month={Jun}, pages={1847–1857} }
 @article{izawa_okuda_ifuku_morimoto_saimoto_rojas_2015, title={Bio-based Wrinkled Surfaces Harnessed from Biological Design Principles of Wood and Peroxidase Activity}, volume={8}, ISSN={["1864-564X"]}, DOI={10.1002/cssc.201500819}, abstractNote={Abstract}, number={22}, journal={CHEMSUSCHEM}, author={Izawa, Hironori and Okuda, Noriko and Ifuku, Shinsuke and Morimoto, Minoru and Saimoto, Hiroyuki and Rojas, Orlando J.}, year={2015}, month={Nov}, pages={3892–3896} }
 @article{carrillo_nypeloe_rojas_2015, title={Cellulose nanofibrils for one-step stabilization of multiple emulsions (W/O/W) based on soybean oil}, volume={445}, ISSN={["1095-7103"]}, DOI={10.1016/j.jcis.2014.12.028}, abstractNote={Cellulose nanofibrils (CNF) were incorporated in water-in-oil (W/O) microemulsions and emulsions, as well as water-in-oil-in-water (W/O/W) multiple emulsions using soybean oil. The addition of CNF to the aqueous phase expanded the composition range to obtain W/O/W emulsions. CNF also increased the viscosity of the continuous phase and reduced the drop size both of which increased the stability and effective viscosity of the emulsions. The effects of oil type and polarity on the properties of the W/O/W emulsions were tested with limonene and octane, which compared to soybean oil produced a smaller emulsion drop size, and thus a higher emulsion viscosity. Overall, CNF are a feasible alternative to conventional polysaccharides as stability enhancers for normal and multiple emulsions that exhibit strong shear thinning behavior.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Carrillo, Carlos A. and Nypeloe, Tiina E. and Rojas, Orlando J.}, year={2015}, month={May}, pages={166–173} }
 @article{rojo_peresin_sampson_hoeger_vartiainen_laine_rojas_2015, title={Comprehensive elucidation of the effect of residual lignin on the physical, barrier, mechanical and surface properties of nanocellulose films}, volume={17}, ISSN={["1463-9270"]}, DOI={10.1039/c4gc02398f}, abstractNote={We elucidate the effect of residual lignin on the interfacial, physical and mechanical properties of lignocellulose nanofibrils (LCNF) and respective nanopapers.}, number={3}, journal={GREEN CHEMISTRY}, author={Rojo, Ester and Peresin, Maria Soledad and Sampson, William W. and Hoeger, Ingrid C. and Vartiainen, Jari and Laine, Janne and Rojas, Orlando J.}, year={2015}, pages={1853–1866} }
 @misc{alvarez_rojas_rojano_ganan_2015, title={Development of self-bonded fiberboards from fiber of leaf plantain: Effect of water and organic extractives removal}, volume={10}, DOI={10.15376/biores.10.1.672-683}, abstractNote={Adhesive-free fiberboards can be self-bonded through high temperature thermo-compression processes. To achieve it, treatments such as steam explosion/injection, as well as chemical and enzymatic oxidation have been implemented. However, the role of extractive components in the structure and cohesiveness of fiberboards has not been fully understood. In this work fibers of leaf plantain were treated with organic solvents and with hot water to remove the extractives, and were then employed to produce self-bonded fiberboards. Treated fibers were characterized by thermogravimetric analysis, electronic paramagnetic resonance, and antioxidant capacity. The mechanical strength of the fiberboards evaluated by three point flexural tests, decreased when fibers were extracted with aqueous solvents, and increased after treatment with organic ones. This can be explained by the effect of water extractives in reducing the initial degradation temperature, and in retaining free stable radicals generated during thermo-compression. In the case of the organic extractive fraction, this inactivates the fibers, which impairs close contact between polar groups and thus decreases the mechanical properties of the fiberboards. According to the results, it is possible to increase the mechanical properties of self-bonded fiberboards by changing the concentration of polar and low molecular weight phenolic compounds.}, number={1}, journal={BioResources}, author={Alvarez, C. and Rojas, O. J. and Rojano, B. and Ganan, P.}, year={2015}, pages={672–683} }
 @article{ferrer_salas_rojas_2015, title={Dewatering of MNFC containing microfibrils and microparticles from soybean hulls: mechanical and transport properties of hybrid films}, volume={22}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-015-0768-y}, number={6}, journal={CELLULOSE}, author={Ferrer, Ana and Salas, Carlos and Rojas, Orlando J.}, year={2015}, month={Dec}, pages={3919–3928} }
 @article{bai_xu_zhang_liu_rojas_2015, title={Dynamics of Cyclodimerization and Viscoelasticity of Photo-Crosslinkable PVA}, volume={53}, ISSN={["1099-0488"]}, DOI={10.1002/polb.23634}, abstractNote={ABSTRACT}, number={5}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Bai, Huiyu and Xu, Jing and Zhang, Yanxia and Liu, Xiaoya and Rojas, Orlando J.}, year={2015}, month={Mar}, pages={345–355} }
 @article{ferrer_vargas_jameel_rojas_2015, title={Influence of operating variables and model to minimize the use of anthraquinone in the soda-anthraquinone pulping of barley straw}, volume={10}, DOI={10.15376/biores.10.4.6442-6456}, abstractNote={Soda-anthraquinone (soda-AQ) pulping of barley straw was used to obtain cellulosic pulps for papermaking purposes. The identified parameters, or variables to be optimized, were operating time, anthraquinone concentration, and PFI refiner revolutions, and the influence of these operating variables on pulp properties was studied. A polynomial model that reproduced the experimental results with errors less than 6% was developed. Operating variables were found (46 min of processing time, 0.4 wt.% of anthraquinone concentration, and 3000 rpm of PFI revolution) that yielded competitive pulp properties (82 °SR beating grade number, 870 mL/g of viscosity, Kappa number of 13, 77 Nm/g of tensile index, and 30% ISO brightness) at reasonable chemical and energy costs. On the other hand, this study highlights the usefulness of this polynomial model as a method to minimize the use of anthraquinone in these pulping processes and to be able to predict what the pulp properties will be. For comparison purposes, new operating conditions were found, and the pulp properties still remain at a very good level for this cereal straw.}, number={4}, journal={BioResources}, author={Ferrer, A. and Vargas, F. and Jameel, H. and Rojas, O. J.}, year={2015}, pages={6442–6456} }
 @article{fritz_ferrer_salas_jameel_rojas_2015, title={Interactions between Cellulolytic Enzymes with Native, Autohydrolysis, and Technical Lignins and the Effect of a Polysorbate Amphiphile in Reducing Nonproductive Binding}, volume={16}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.5b01203}, abstractNote={Understanding enzyme-substrate interactions is critical in designing strategies for bioconversion of lignocellulosic biomass. In this study we monitored molecular events, in situ and in real time, including the adsorption and desorption of cellulolytic enzymes on lignins and cellulose, by using quartz crystal microgravimetry and surface plasmon resonance. The effect of a nonionic surface active molecule was also elucidated. Three lignin substrates relevant to the sugar platform in biorefinery efforts were considered, namely, hardwood autohydrolysis cellulolytic (HWAH), hardwood native cellulolytic (MPCEL), and nonwood native cellulolytic (WSCEL) lignin. In addition, Kraft lignins derived from softwoods (SWK) and hardwoods (HWK) were used as references. The results indicated a high affinity between the lignins with both, monocomponent and multicomponent enzymes. More importantly, the addition of nonionic surfactants at concentrations above their critical micelle concentration reduced remarkably (by over 90%) the nonproductive interactions between the cellulolytic enzymes and the lignins. This effect was hypothesized to be a consequence of the balance of hydrophobic and hydrogen bonding interactions. Moreover, the reduction of surface roughness and increased wettability of lignin surfaces upon surfactant treatment contributed to a lower affinity with the enzymes. Conformational changes of cellulases were observed upon their adsorption on lignin carrying preadsorbed surfactant. Weak electrostatic interactions were determined in aqueous media at pH between 4.8 and 5.5 for the native cellulolytic lignins (MPCEL and WSCEL), whereby a ∼20% reduction in the enzyme affinity was observed. This was mainly explained by electrostatic interactions (osmotic pressure effects) between charged lignins and cellulases. Noteworthy, adsorption of nonionic surfactants onto cellulose, in the form cellulose nanofibrils, did not affect its hydrolytic conversion. Overall, our results highlight the benefit of nonionic surfactant pretreatment to reduce nonproductive enzyme binding while maintaining the reactivity of the cellulosic substrate.}, number={12}, journal={BIOMACROMOLECULES}, author={Fritz, Consuelo and Ferrer, Ana and Salas, Carlos and Jameel, Hasan and Rojas, Orlando J.}, year={2015}, month={Dec}, pages={3878–3888} }
 @article{bai_li_wang_chen_rojas_dong_liu_2015, title={Interpenetrated polymer networks in composites with poly(vinyl alcohol), micro- and nano-fibrillated cellulose (M/NFC) and polyHEMA to develop packaging materials}, volume={22}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-015-0748-2}, number={6}, journal={CELLULOSE}, author={Bai, Huiyu and Li, Yufei and Wang, Wei and Chen, Guangliang and Rojas, Orlando J. and Dong, Weifu and Liu, Xiaoya}, year={2015}, month={Dec}, pages={3877–3894} }
 @article{nypeloe_carrillo_rojas_2015, title={Lignin supracolloids synthesized from (W/O) microemulsions: use in the interfacial stabilization of Pickering systems and organic carriers for silver metal}, volume={11}, ISSN={["1744-6848"]}, DOI={10.1039/c4sm02851a}, abstractNote={Taking advantage of the aromatic and cross-linking tendency of lignin macromolecules extracted from plants, we present a novel method for their assembly into supracolloidal structures. Specifically, spherical particles with controllable size (∼90 nm to 1 μm) were obtained from water-in-oil (W/O) microemulsions formulated with a mixture of nonionic surfactants and a colloidal dispersion of a low molecular weight alkali lignin. After spontaneous emulsification, the internal lignin-rich phase was cross-linked to produce the solid particles that could be easily separated by removal of the organic, continuous phase. The efficiency of the fractionated lignin particles to stabilize hexadecane-in-water Pickering emulsions was demonstrated and their properties were compared against those obtained by using traditional inorganic particles. The effect of the particle size of lignin on the emulsion structure is discussed. As a proof of concept we further introduce the use of related emulsions to enable in situ reduction of silver and loading of silver nanoparticles in lignin carriers.}, number={10}, journal={SOFT MATTER}, author={Nypeloe, Tiina E. and Carrillo, Carlos A. and Rojas, Orlando J.}, year={2015}, month={Mar}, pages={2046–2054} }
 @article{ogunkoya_li_rojas_fang_2015, title={Performance, combustion, and emissions in a diesel engine operated with fuel-in-water emulsions based on lignin}, volume={154}, ISSN={["1872-9118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84930675094&partnerID=MN8TOARS}, DOI={10.1016/j.apenergy.2015.05.036}, abstractNote={We report for the first time on the use of water-continuous emulsions stabilized by a bio-based macromolecule in a compression-ignition diesel engine and compare their performance, combustion and emissions against the base fuels (diesel, biodiesel, and jet fuel). For this purpose, high internal phase ratio emulsions (70:30 fuel-to-water) were produced by mechanical emulsification using carboxymethylated wood lignin as stabilizer. Combusting experiments were performed with the engine operating at 2000 rpm under three loads (0, 1.26 and 3.26 bar brake mean effective pressure, BMEP). Engine performance, in-cylinder combustion, and exhaust emissions were monitored and compared for the fuels tested. At no load condition and when compared to the respective base (single phase) fuels, an increase in the indicated work was observed for diesel and biodiesel emulsions. Compared to the base fuels, the emulsions resulted in higher engine mechanical efficiency at 1.26 and 3.26 bar BMEP except for jet fuel emulsion at 1.26 bar. Additionally, they displayed a lower brake specific fuel consumption (BSFC), if calculated on the basis of effective fuel content discounting emulsion water, and higher brake thermal efficiency. Compared to the base fuel, the respective emulsions generally presented lower peak in-cylinder pressure, lower heat release rates, and longer ignition delays at 1.26 bar and 3.26 bar BMEP; the opposite effect was observed at no-load conditions. Remarkably, a large reduction of nitrogen oxides (NOx) emissions was noted in the combustion of the fuel emulsions, which was accompanied with a relatively higher carbon monoxide (CO) release at 1.26 and 3.26 bar (at 0 bar BMEP, the emulsions produced less CO emissions). The effect of emulsions on hydrocarbon emissions and smoke opacity depended on the fuel type and the engine load. Overall, it is concluded that while reports on fuel emulsions involve oil-continuous systems, the proposed water-continuous alternative represents an opportunity for diesel engines, whereby the fuel is dispersed as micrometric droplets for improved combustion and reduced emissions. At the same time, the fuel emulsion formulation takes advantage of the surface activity and high calorific value of widely available, inexpensive lignin stabilizers, making the proposed system a viable option towards cleaner or fully bio-based fuels.}, journal={APPLIED ENERGY}, author={Ogunkoya, Dolanimi and Li, Shuai and Rojas, Orlando J. and Fang, Tiegang}, year={2015}, month={Sep}, pages={851–861} }
 @article{song_salas_rojas_2015, title={Role of textile substrate hydrophobicity on the adsorption of hydrosoluble nonionic block copolymers}, volume={454}, ISSN={["1095-7103"]}, DOI={10.1016/j.jcis.2015.04.061}, abstractNote={The adsorption of polyalkylene glycols and co-polymers of ethylene oxide and propylene oxide on substrates relevant to textiles with varying surface energies (cellulose, polypropylene, nylon and polyester) was studied by using quartz crystal microgravimetry. Langmuirian-type isotherms were observed for the adsorption profiles of nonionic block polymers of different architectures. The affinity with the surfaces is discussed based on experimental observations, which highlights the role of hydrophobic effects. For a given type of block polymer, micellar and monomeric adsorption is governed by the balance of polymer structure (mainly, chain length of hydrophobic segments) and substrate's surface energy.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Song, Junlong and Salas, Carlos and Rojas, Orlando J.}, year={2015}, month={Sep}, pages={89–96} }
 @article{langdon_mirhossaini_mabry_sriram_lajmi_zhang_rojas_schwartz_2015, title={Single-Molecule Resolution of Protein Dynamics on Polymeric Membrane Surfaces: The Roles of Spatial and Population Heterogeneity}, volume={7}, ISSN={["1944-8252"]}, DOI={10.1021/am507730k}, abstractNote={Although polymeric membranes are widely used in the purification of protein pharmaceuticals, interactions between biomolecules and membrane surfaces can lead to reduced membrane performance and damage to the product. In this study, single-molecule fluorescence microscopy provided direct observation of bovine serum albumin (BSA) and human monoclonal antibody (IgG) dynamics at the interface between aqueous buffer and polymeric membrane materials including regenerated cellulose and unmodified poly(ether sulfone) (PES) blended with either polyvinylpyrrolidone (PVP), polyvinyl acetate-co-polyvinylpyrrolidone (PVAc-PVP), or polyethylene glycol methacrylate (PEGM) before casting. These polymer surfaces were compared with model surfaces composed of hydrophilic bare fused silica and hydrophobic trimethylsilane-coated fused silica. At extremely dilute protein concentrations (10(-3)-10(-7) mg/mL), protein surface exchange was highly dynamic with protein monomers desorbing from the surface within ∼1 s after adsorption. Protein oligomers (e.g., nonspecific dimers, trimers, or larger aggregates), although less common, remained on the surface for 5 times longer than monomers. Using newly developed super-resolution methods, we could localize adsorption sites with ∼50 nm resolution and quantify the spatial heterogeneity of the various surfaces. On a small anomalous subset of the adsorption sites, proteins adsorbed preferentially and tended to reside for significantly longer times (i.e., on "strong" sites). Proteins resided for shorter times overall on surfaces that were more homogeneous and exhibited fewer strong sites (e.g., PVAc-PVP/PES). We propose that strong surface sites may nucleate protein aggregation, initiated preferentially by protein oligomers, and accelerate ultrafiltration membrane fouling. At high protein concentrations (0.3-1.0 mg/mL), fewer strong adsorption sites were observed, and surface residence times were reduced. This suggests that at high concentrations, adsorbed proteins block strong sites from further protein adsorption. Importantly, this demonstrates that strong binding sites can be modified by changing solution conditions. Membrane surfaces are intrinsically heterogeneous; by employing single-molecule techniques, we have provided a new framework for understanding protein interactions with such surfaces.}, number={6}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Langdon, Blake B. and Mirhossaini, Roya B. and Mabry, Joshua N. and Sriram, Indira and Lajmi, Ajay and Zhang, Yanxia and Rojas, Orlando J. and Schwartz, Daniel K.}, year={2015}, month={Feb}, pages={3607–3617} }
 @article{wang_hauser_rojas_2015, title={Study on charge distribution of carboxymethylated cotton fabric by streaming potential/current measurements}, volume={2}, DOI={10.14504/ajr.2.2.2}, abstractNote={Carboxymethylated cotton might provide an eco-friendly novel approach to impart different functions to fabric by crosslinking or self-assembly deposition of nanolayers. The anionic content of carboxymethylated cotton was determined by acid-base titration. Two interrelated methods of surface electrochemistry for anionic cotton fabrics were investigated in this paper. Measurement of surface charge on carboxymethylated cotton was achieved by characterizing the zeta potential of the anionized fibers via streaming current (SC) and fiber-pad streaming potential (SP) measurements, which showed only a small percentage of total charges contributed to the surface charge. SC and SP methods were proven to be useful in studying the surface charge of ionic cellulose.}, number={2}, journal={AATCC Journal of Research}, author={Wang, Z. J. and Hauser, P. J. and Rojas, O. J.}, year={2015}, pages={13–19} }
 @article{cusola_blanca roncero_vidal_rojas_2014, title={A Facile and Green Method to Hydrophobize Films of Cellulose Nanofibrils and Silica by Laccase-Mediated Coupling of Nonpolar Colloidal Particles}, volume={7}, ISSN={["1864-564X"]}, DOI={10.1002/cssc.201402432}, abstractNote={Abstract}, number={10}, journal={CHEMSUSCHEM}, author={Cusola, Oriol and Blanca Roncero, M. and Vidal, Teresa and Rojas, Orlando J.}, year={2014}, month={Oct}, pages={2868–2878} }
 @article{junka_filpponen_johansson_kontturi_rojas_laine_2014, title={A method for the heterogeneous modification of nanofibrillar cellulose in aqueous media}, volume={100}, ISSN={["1879-1344"]}, DOI={10.1016/j.carbpol.2012.11.063}, abstractNote={Cellulosic substrates were modified by using sequential adsorption of functionalized carboxymethyl cellulose (CMC) and “click” chemistry in aqueous media. First, the effect of degree of substitution (DS), and level of functionalization as well as ionic strength of the medium were systematically investigated in situ by using quartz crystal microbalance with dissipation (QCM-D) in terms of the extent of adsorption of propargyl and azido functionalized CMC. It was found that the functionalization of CMC did not prevent its adsorption on cellulose. However, it was only effective in the presence of electrolytes. Moreover, the adsorption was found to be more efficient for the functionalized CMCs with low initial DS. Next, “click” chemistry, copper (I)-catalyzed azide-alkyne cycloaddition reaction (CuAAC), was carried out for covalent attachment of different molecules on the pre-functionalized ultrathin cellulose films. The modified cellulosic surfaces were further characterized using AFM imaging and XPS. Finally, the method was successfully used in modification of nanofibrillar cellulose (NFC) in aqueous media.}, journal={CARBOHYDRATE POLYMERS}, author={Junka, Karoliina and Filpponen, Ilari and Johansson, Leena-Sisko and Kontturi, Eero and Rojas, Orlando J. and Laine, Janne}, year={2014}, month={Jan}, pages={107–115} }
 @article{arboleda_rojas_lucia_2014, title={Acid-Generated Soy Protein Hydrolysates and Their Interfacial Behavior on Model Surfaces}, volume={15}, ISSN={["1526-4602"]}, DOI={10.1021/bm501344j}, abstractNote={The present work attempts to provide data to warrant the consideration of soy proteins (SP) as potentially useful biomolecules for practical chemical and surface applications. Despite their sundry properties, SP use has been limited by their high molecular weight. In response to this limitation, we analyze acid hydrolysates of soy proteins (0.1 N HCl, 70 °C) for surface modification. Techniques typical in protein (SDS-PAGE) as well as colloidal (charge demand and electrophoretic mobility) analyses were used to follow the effects of molecular changes that occur upon hydrolysis. Adsorption experiments on hydrophobic (polypropylene) and mineral (aluminum oxide) surfaces were subsequently carried out to further interrogate the surface activity resultant from soy hydrolysis. It was found that during adsorption the hydrolysates tended to form less surface aggregates and adsorbed at faster rates compared with unmodified SP. Overall, the benefits derived from the application of SP hydrolysates are highlighted.}, number={11}, journal={BIOMACROMOLECULES}, author={Arboleda, Julio C. and Rojas, Orlando J. and Lucia, Lucian A.}, year={2014}, month={Nov}, pages={4336–4342} }
 @article{song_krause_rojas_2014, title={Adsorption of polyalkyl glycol ethers and triblock nonionic polymers on PET}, volume={420}, ISSN={["1095-7103"]}, DOI={10.1016/j.jcis.2014.01.012}, abstractNote={Surface modification enables fiber lubrication and processing but little is known about the extent and dynamics of adsorption of typical adsorbates applied for such purposes, which often includes water-soluble block nonionic amphiphilic polymers. In this work we used quartz crystal microgravimetry (QCM) to investigate the adsorption on poly(ethylene terephthalate) (PET) of polyalkyl glycol ethers and triblock molecules of ethylene oxide and propylene oxide. The adsorption from aqueous solution of the block nonionic amphiphilic polymers strongly correlated with the self-association driven by the chain length of the respective hydrophobic blocks. This was demonstrated for the different adsorbing polymers using hydrophobic numbers calculated from simple group contribution methods. Hydrophobic and van der Waals interactions explain the affinity of the nonionic polymers with PET, which lead to adsorption isotherms that follow Langmuir-based and one-step empirical adsorption models.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Song, Junlong and Krause, Wendy E. and Rojas, Orlando J.}, year={2014}, month={Apr}, pages={174–181} }
 @article{orelma_morales_johansson_hoeger_filpponen_castro_rojas_laine_2014, title={Affibody conjugation onto bacterial cellulose tubes and bioseparation of human serum albumin}, volume={4}, DOI={10.1039/c4ra08882d}, abstractNote={We attached anti-human serum albumin (anti-HSA) affibody ligands on bacterial cellulose (BC) by EDC–NHS-mediated covalent conjugation and physical adsorption and demonstrate their application for tubular biofiltration of blood proteins.}, number={93}, journal={RSC Advances}, author={Orelma, H. and Morales, L. O. and Johansson, L. S. and Hoeger, I. C. and Filpponen, I. and Castro, C. and Rojas, O. J. and Laine, J.}, year={2014}, pages={51440–51450} }
 @article{abdelgawad_hudson_rojas_2014, title={Antimicrobial wound dressing nanofiber mats from multicomponent (chitosan/silver-NPs/polyvinyl alcohol) systems}, volume={100}, ISSN={["1879-1344"]}, DOI={10.1016/j.carbpol.2012.12.043}, abstractNote={Novel hybrid nanomaterials have been developed for antimicrobial applications. Here we introduce a green route to produce antibacterial nanofiber mats loaded with silver nanoparticles (Ag-NPs, 25 nm diameter) enveloped in chitosan after reduction with glucose. The nanofiber mats were obtained from colloidal dispersions of chitosan-based Ag-NPs blended with polyvinyl alcohol. Nanofibers (150 nm average diameter and narrow size distribution) were obtained by electrospinning and cross-linked with glutaraldhyde. The effect of crosslinking on the release of silver was studied by atomic absorption spectroscopy. Antimicrobial activity was studied by the viable cell-counting; mats loaded with silver and control samples (chitosan/PVA) with different degrees of cross-linking were compared for their effectiveness in reducing or halting the growth of aerobic bacteria. The results showed superior properties and synergistic antibacterial effects by combining chitosan with Ag-NPs.}, journal={CARBOHYDRATE POLYMERS}, author={Abdelgawad, Abdelrahman M. and Hudson, Samuel M. and Rojas, Orlando J.}, year={2014}, month={Jan}, pages={166–178} }
 @article{arcot_lundahl_rojas_laine_2014, title={Asymmetric cellulose nanocrystals: thiolation of reducing end groups via NHS-EDC coupling}, volume={21}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-014-0426-9}, number={6}, journal={CELLULOSE}, author={Arcot, Lokanathan R. and Lundahl, Meri and Rojas, Orlando J. and Laine, Janne}, year={2014}, month={Dec}, pages={4209–4218} }
 @article{lokanathan_uddin_rojas_laine_2014, title={Cellulose Nanocrystal-Mediated Synthesis of Silver Nanoparticles: Role of Sulfate Groups in Nucleation Phenomena}, volume={15}, ISSN={["1526-4602"]}, DOI={10.1021/bm401613h}, abstractNote={Developing sustainable chemical methods to synthesize silver nanoparticles has drawn significant research interest. Due to their unique and well-defined physical-chemical properties, cellulose nanocrystals (CNCs) have become one of the most promising renewable nanomaterials. Here we use CNC to mediate silver nanoparticle synthesis and elucidate the effect of CNC surface chemistry (as defined by sulfate groups) in nanoparticle formation and nucleation in the presence of borohydride reduction. Pristine CNCs produced by sulfuric acid hydrolysis and partially desulfated CNCs mediated the formation of silver nanoparticles of different sizes (and size distribution) following different rates of formation, as determined by transmission electron microscopy (TEM) and UV-vis spectroscopy. The results shed light on methods to stabilize silver nanoparticles, control their nucleation, and highlight the potential of CNCs in metal nanoparticle synthesis.}, number={1}, journal={BIOMACROMOLECULES}, author={Lokanathan, Arcot R. and Uddin, Khan Mohammad Ahsan and Rojas, Orlando J. and Laine, Janne}, year={2014}, month={Jan}, pages={373–379} }
 @article{peresin_vesterinen_habibi_johansson_pawlak_nevzorov_rojas_2014, title={Crosslinked PVA nanofibers reinforced with cellulose nanocrystals: Water interactions and thermomechanical properties}, volume={131}, ISSN={0021-8995}, url={http://dx.doi.org/10.1002/APP.40334}, DOI={10.1002/app.40334}, abstractNote={ABSTRACT}, number={11}, journal={Journal of Applied Polymer Science}, publisher={Wiley}, author={Peresin, Maria Soledad and Vesterinen, Arja-Helena and Habibi, Youssef and Johansson, Leena-Sisko and Pawlak, Joel J. and Nevzorov, Alexander A. and Rojas, Orlando J.}, year={2014}, month={Jan}, pages={n/a-n/a} }
 @article{islam_shen_gurgel_rojas_carbonell_2014, title={Dynamic and equilibrium performance of sensors based on short peptide ligands for affinity adsorption of human IgG using surface plasmon resonance}, volume={58}, ISSN={["1873-4235"]}, DOI={10.1016/j.bios.2014.02.069}, abstractNote={This paper characterizes the potential of novel hexameric peptide ligands for on-line IgG detection in bioprocesses. Surface Plasmon Resonance (SPR) was used to study the binding of human IgG to the hexameric peptide ligand HWRGWV, which was covalently grafted to alkanethiol self-assembled monolayers (SAM) on gold surfaces. Peptide coupling on SAMs was verified, followed by covalent grafting of peptides with a removable Fmoc or acetylated N-termini via their C-termini to produce active peptide SPR sensors that were tested for IgG binding. The dynamics and extent of peptide–IgG binding were compared with results from a conventional system using protein A attached on a gold surface via disulfide monolayers. IgG binding to protein A on disulfide monolayers yielded equilibrium dissociation constants of 1.4×10–7 M. The corresponding dissociation constant value for the acetylated version of the peptide (Ac-HWRGWV) supported on alkanethiol SAM was 5.8×10–7 M and that for HWRGWV on the alkanethiol SAM (after de-protection of Fmoc-HWRGWVA) was 1.2×10–6 M. Maximum IgG binding capacities, Qm of 6.7, 3.8, and 4.1 mg m−2 were determined for the protein A and the two forms of HWRGWV-based biosensors, respectively. Real-time data for the kinetics of adsorption were used to determine the apparent rate constants for adsorption and desorption. The results were analyzed to understand the mechanism of IgG binding to the protein and peptide ligands. It was found that the peptide–IgG binding was reaction controlled, however the protein A–IgG binding mechanism was partially mass transfer (diffusion) controlled. The adsorption rate constants, ka, for the protein A ligand increased with decreasing concentration of analyte and the peptide ligand ka values was constant at different IgG concentrations and flow rates.}, journal={BIOSENSORS & BIOELECTRONICS}, author={Islam, Nafisa and Shen, Fei and Gurgel, Patrick V. and Rojas, Orlando J. and Carbonell, Ruben G.}, year={2014}, month={Aug}, pages={380–387} }
 @article{islam_gurgel_rojas_carbonell_2014, title={Effects of Composition of Oligo(ethylene glycol)-Based Mixed Monolayers on Peptide Grafting and Human Immunoglobulin Detection}, volume={118}, ISSN={["1932-7455"]}, DOI={10.1021/jp411469u}, abstractNote={Alkanethiols carrying ethylene glycol units (EGn, n = 3 or 6) with amine termini (EG3NH2 or EG6NH2) were coadsorbed with a “diluent”, hydroxyl-terminated alkanethiol (EG3OH), to form mixed self-assembled monolayers (SAMs). The mixed SAMs were characterized, and hexameric peptide ligand His-Trp-Arg-Gly-Trp-Val (HWRGWV), which shows affinity binding toward the Fc (constant fragment) of human immunoglobulin (IgG), was grafted onto different dilutions of EG6NH2–EG3OH mixed SAMs for preparation of IgG detection surfaces. The specificity toward IgG was optimal for peptides grafted on SAMs prepared from 10% EG6NH2 precursor solution, even though this surface did not have the highest number of peptides per unit area. Surface plasmon resonance (SPR) experiments showed that IgG bound to the peptides on the mixed SAM with a dissociation constant Kd of 9.33 × 10–7, maximum binding capacity Qm of 3.177 mg m–2, and adsorption rate constant ka of 1.99 m3 mol–1 s–1. IgG binding from complex mixtures of Chinese Hamster Ov...}, number={10}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Islam, Nafisa and Gurgel, Patrick V. and Rojas, Orlando J. and Carbonell, Ruben G.}, year={2014}, month={Mar}, pages={5361–5373} }
 @article{morales_iakovlev_martin-sampedro_rahikainen_laine_heiningen_rojas_2014, title={Effects of residual lignin and heteropolysaccharides on the bioconversion of softwood lignocellulose nanofibrils obtained by SO2-ethanol-water fractionation}, volume={161}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2014.03.025}, abstractNote={The amount of residual lignin and hemicelluloses in softwood fibers was systematically varied by SO2-ethanol-water fractionation for integrated biorefinery with nanomaterial and biofuel production. On the basis of their low energy demand in mechanical processing, the fibers were deconstructed to lignocellulose nanofibrils (LCNF) and used as substrate for bioconversion. The effect of LCNF composition on saccharification via multicomponent enzymes was investigated at different loadings. LCNF digestibility was compared with the enzyme activity measured with a quartz crystal microbalance. LCNF hydrolysis rate gradually decreased with lignin and hemicellulose concentration, both of which limited enzyme accessibility. Enzyme inhibition resulted from non-productive binding of proteins onto lignin. Near complete LCNF hydrolysis was achieved, even at high lignin and hemicellulose content. Sugar yields for LCNF were higher than those for precursor SEW fibers, highlighting the benefits of high surface area in LCNF.}, journal={BIORESOURCE TECHNOLOGY}, author={Morales, Luis O. and Iakovlev, Mikhail and Martin-Sampedro, Raquel and Rahikainen, Jenni L. and Laine, Janne and Heiningen, Adriaan and Rojas, Orlando J.}, year={2014}, month={Jun}, pages={55–62} }
 @article{castro_vesterinen_zuluaga_caro_filpponen_rojas_kortaberria_ganan_2014, title={In situ production of nanocomposites of poly(vinyl alcohol) and cellulose nanofibrils from Gluconacetobacter bacteria: effect of chemical crosslinking}, volume={21}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-014-0170-1}, number={3}, journal={CELLULOSE}, author={Castro, Cristina and Vesterinen, Arja and Zuluaga, Robin and Caro, Gloria and Filpponen, Ilari and Rojas, Orlando J. and Kortaberria, Galder and Ganan, Piedad}, year={2014}, month={Jun}, pages={1745–1756} }
 @article{nypeloe_rodriguez-abreu_rivas_dickey_rojas_2014, title={Magneto-responsive hybrid materials based on cellulose nanocrystals}, volume={21}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-014-0307-2}, number={4}, journal={CELLULOSE}, publisher={Springer Nature}, author={Nypeloe, Tiina and Rodriguez-Abreu, Carlos and Rivas, Jose and Dickey, Michael D. and Rojas, Orlando J.}, year={2014}, month={Aug}, pages={2557–2566} }
 @article{nypeloe_rodriguez-abreu_kolen'ko_rivas_rojas_2014, title={Microbeads and Hollow Microcapsules Obtained by Self-Assembly of Pickering Magneto-Responsive Cellulose Nanocrystals}, volume={6}, ISSN={["1944-8252"]}, DOI={10.1021/am504260u}, abstractNote={Cellulose microbeads can be used as immobilization supports. We report on the design and preparation of magneto-responsive cellulose microbeads and microcapsules by self-assembled shells of cellulose nanocrystals (CNC) carrying magnetic CoFe2O4 nanoparticles, that is, a mixture of isotropic and anisotropic nanomaterials. The magnetic CNCs formed a structured layer, a mesh, consisting of CNCs and magnetic particles bound together on the surface of distinct droplets of hexadecane and styrene dispersed in water. Because of the presence of CNCs the highly crystalline mesh was targeted to provide an improved barrier property of the microbead shell compared to neat polymer shells, while the magnetic particles provided the magnetic response. In situ polymerization of the styrene phase led to the formation of solid microbeads (∼8 μm diameter) consisting of polystyrene (PS) cores encapsulated in the magnetic CNC shells (shell-to-core mass ratio of 4:96). The obtained solid microbeads were ferromagnetic (saturation magnetization of ∼60 emu per gram of the magnetic phase). The magnetic functionality enables easy separation of substances immobilized on the beads. Such a functionality was tested in removal of a dye from water. The microbeads were further utilized to synthesize hollow microcapsules by solubilization of the PS core. The CNC-based, magneto-responsive solid microbeads and hollow microcapsules were characterized by electron microscopy (morphology), X-ray diffraction (phase composition), and magnetometry (magnetic properties). Such hybrid systems can be used in the design of materials and devices for application in colloidal stabilization, concentration, separation, and delivery, among others.}, number={19}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Nypeloe, Tiina and Rodriguez-Abreu, Carlos and Kolen'ko, Yury V. and Rivas, Jose and Rojas, Orlando J.}, year={2014}, month={Oct}, pages={16851–16858} }
 @article{carrillo_laine_rojas_2014, title={Microemulsion Systems for Fiber Deconstruction into Cellulose Nanofibrils}, volume={6}, ISSN={["1944-8252"]}, DOI={10.1021/am5067332}, abstractNote={A new method to produce cellulose nanofibrils (CNF) is proposed to reduce the energy demand during deconstruction of precursor fibers suspended in aqueous media. Microemulsions were formulated with aqueous solutions of urea or ethylenediamine and applied to disrupt interfibril hydrogen bonding. Compared to typical fibrillation of lignin-containing and lignin-free fibers, pretreatment with microemulsion systems allowed energy savings during microfluidization of 55 and 32%, respectively. Moreover, microemulsion processing facilitated smaller-scale CNF structures (higher degrees of deconstruction), with higher water retention value (WRV) and surface area. Urea-containing microemulsions were found to be most effective in reducing energy consumption and in weakening the cellulosic matrix. Films prepared from CNF processed after pretreatment with urea-containing microemulsions presented a more uniform fiber network and produced films with smoother surfaces compared to those based on ethylenediamine. The lignin-containing CNF (LCNF) produced denser films than those obtained from lignin-free CNF. The mechanical properties of films obtained after application of microemulsion pretreatment were compared, and the benefits of the proposed approach were further confirmed. Overall, fiber deconstruction after microemulsion treatment is a step toward energy-efficient production of nanocellulose.}, number={24}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Carrillo, Carlos A. and Laine, Janne and Rojas, Orlando J.}, year={2014}, month={Dec}, pages={22622–22627} }
 @article{junka_guo_filpponen_laine_rojas_2014, title={Modification of Cellulose Nanofibrils with Luminescent Carbon Dots}, volume={15}, ISSN={["1526-4602"]}, DOI={10.1021/bm4017176}, abstractNote={Films and hydrogels consisting of cellulose nanofibrils (CNF) were modified by covalent EDC/NHS coupling of luminescent, water-dispersible carbon dots (CDs). Quartz crystal microgravimetry with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR) were used to investigate the attachment of CDs on carboxymethylated CNF (CM-CNF). As the first reported use of CD in nanocellulose products, we provide proof-of-concept for the synthesis of transparent and fluorescent nanopaper and for its tunable luminescence as confirmed by confocal microscopy imaging.}, number={3}, journal={BIOMACROMOLECULES}, author={Junka, Karoliina and Guo, Jiaqi and Filpponen, Ilari and Laine, Janne and Rojas, Orlando J.}, year={2014}, month={Mar}, pages={876–881} }
 @article{quddus_rojas_pasquinelli_2014, title={Molecular Dynamics Simulations of the Adhesion of a Thin Annealed Film of Oleic Acid onto Crystalline Cellulose}, volume={15}, ISSN={["1526-4602"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84898618457&partnerID=MN8TOARS}, DOI={10.1021/bm500088c}, abstractNote={Molecular dynamics simulations were used to characterize the wetting behavior of crystalline cellulose planes in contact with a thin oily film of oleic acid. Cellulose crystal planes with higher molecular protrusions and increased surface area produced stronger adhesion if compared to other crystal planes due to enhanced wetting and hydrogen bonding. The detailed characteristics of crystal plane features and the contribution of directional hydrogen bonding was investigated. Similarly, oleophilicity of the cellulose planes increased with the increase in surface roughness and number of directional hydrogen bonds. These results correlate with conclusions drawn from experimental studies such as adhesion of an ink vehicle on cellulose surface.}, number={4}, journal={BIOMACROMOLECULES}, publisher={American Chemical Society (ACS)}, author={Quddus, Mir A. A. R. and Rojas, Orlando J. and Pasquinelli, Melissa A.}, year={2014}, month={Apr}, pages={1476–1483} }
 @article{hoeger_gleisner_negron_rojas_zhu_2014, title={Mountain Pine Beetle-Killed Lodgepole Pine for the Production of Submicron Lignocellulose Fibrils}, volume={60}, ISSN={["1938-3738"]}, DOI={10.5849/forsci.13-012}, abstractNote={The elevated levels of tree mortality attributed to mountain pine beetle (MPB) (Dendroctonus ponderosae Hopkins) in western North American forests create forest management challenges. This investigation introduces the production of submicron or nanometer lignocellulose fibrils for value-added materials from the widely available resource represented by dead pines after an outbreak. Lodgepole pine (Pinus contorta Dougl. ex Loud.), trees from two different times since infestation and a noninfested live tree as a control were used for mechanical fibrillation. Fiber deconstruction down to the micro-/nanoscale from infested wood was performed using mechanical fibrillation, without any chemical (pre)treatment. The effects of fibrillation were monitored as a function of processing time, and the respective products were characterized. The changes in fibril morphology, cellulose crystallinity, water retention value, and cellulase adsorption capacity were determined. Interestingly, no significant differences were found between fibrillated samples from the live and the MPB-killed trees. It can be concluded that MPB-killed lodgepole pine is a suitable feedstock for the production of lignocellulose micro-/nanofibrils.}, number={3}, journal={FOREST SCIENCE}, author={Hoeger, Ingrid and Gleisner, Rolland and Negron, Jose and Rojas, Orlando J. and Zhu, J. Y.}, year={2014}, month={Jun}, pages={502–511} }
 @misc{salas_nypeloe_rodriguez-abreu_carrillo_rojas_2014, title={Nanocellulose properties and applications in colloids and interfaces}, volume={19}, ISSN={["1879-0399"]}, DOI={10.1016/j.cocis.2014.10.003}, abstractNote={In this review we introduce recent advances in the development of cellulose nanomaterials and the construction of high order structures by applying some principles of colloid and interface science. These efforts take advantage of natural assemblies in the form of fibers that nature constructs by a biogenetic bottom-up process that results in hierarchical systems encompassing a wide range of characteristic sizes. Following the reverse process, a top-down deconstruction, cellulose materials can be cleaved from fiber cell walls. The resulting nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like crystalline residues after acid hydrolysis of fibers), have been the subject of recent interest. This originates from the appealing intrinsic properties of nanocelluloses: nanoscale dimensions, high surface area, morphology, low density, chirality and thermo-mechanical performance. Directing their assembly into multiphase structures is a quest that can yield useful outcomes in many revolutionary applications. As such, we discuss the use of non-specific forces to create thin films of nanocellulose at the air–solid interface for applications in nano-coatings, sensors, etc. Assemblies at the liquid–liquid and air–liquid interfaces will be highlighted as means to produce Pickering emulsions, foams and aerogels. Finally, the prospects of a wide range of hybrid materials and other systems that can be manufactured via self and directed assembly will be introduced in light of the unique properties of nanocelluloses.}, number={5}, journal={CURRENT OPINION IN COLLOID & INTERFACE SCIENCE}, author={Salas, Carlos and Nypeloe, Tiina and Rodriguez-Abreu, Carlos and Carrillo, Carlos and Rojas, Orlando J.}, year={2014}, month={Oct}, pages={383–396} }
 @article{arboleda_niemi_kumpunen_lucia_rojas_2014, title={Soy Protein-Based Polyelectrolyte Complexes as Biobased Wood Fiber Dry Strength Agents}, volume={2}, ISSN={["2168-0485"]}, DOI={10.1021/sc500399d}, abstractNote={Soy protein flour, isolate, and their derivatives were investigated to enhance the dry strength properties of paper. The soy systems were applied in aqueous suspensions consisting of lignin-free and recycled fibers to investigate their adsorption and interaction effects. Experiments using soy flour, soy protein isolate and its hydrolysates, cationized soy flour, and dual systems consisting of soy flour combined with cationic starch or chitosan were pursued. Improved paper strength was obtained when soy protein flour was utilized in combination with conventional treatments based on cationic polymers. For example, increases in ultimate tensile and compressive strength of lignin-free fiber paper of 23% and 10%, respectively, were measured when dual systems consisting of soy flour and cationic starch were applied relative to the fibers with no additive. In the case of lignin-containing recycled fibers, improvements of 52% and 56%, respectively, were obtained for a soy flour–chitosan dual system (compared to f...}, number={10}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Arboleda, Julio C. and Niemi, Niko and Kumpunen, Juha and Lucia, Lucian A. and Rojas, Orlando J.}, year={2014}, month={Oct}, pages={2267–2274} }
 @article{osorio_restrepo_velasquez-cock_zuluaga_montoya_rojas_ganan_marin_castro_2014, title={Synthesis of Thermoplastic Starch-Bacterial Cellulose Nanocomposites via in situ Fermentation}, volume={25}, ISSN={["1678-4790"]}, DOI={10.5935/0103-5053.20140146}, abstractNote={In this paper, a nanocomposite based on thermoplastic starch (TPS) reinforced with bacterial cellulose (BC) nanoribbons was synthesized by in situ fermentation and chemical crosslinking. BC nanoribbons were produced by a Colombian native strain of Gluconacetobacter medellinensis; the nanocomposite was plasticized with glycerol and crosslinked with citric acid. The reinforcement percentage in the nanocomposites remained constant throughout the fermentation time because of the TPS absorption capability of the BC network. Nanocomposites produced after fermentation for seven days were characterized using thermogravimetric analysis (TGA); Fourier transformed infrared spectroscopy with attenuated total reflectance (FTIR-ATR), mechanical testing and scanning electron microscopy (SEM). The new TPS/BC nanocomposites exhibit strong interfacial adhesion, improved thermal behavior, water stability and enhanced mechanical properties. These findings support the applications of starch in the packaging industry.}, number={9}, journal={JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY}, author={Osorio, Marlon A. and Restrepo, David and Velasquez-Cock, Jorge A. and Zuluaga, Robin O. and Montoya, Ursula and Rojas, Orlando and Ganan, Piedad F. and Marin, Diana and Castro, Cristina I.}, year={2014}, month={Sep}, pages={1607–1613} }
 @article{salas_ago_lucia_rojas_2014, title={Synthesis of soy protein-lignin nanofibers by solution electrospinning}, volume={85}, ISSN={["1873-166X"]}, DOI={10.1016/j.reactfunctpolym.2014.09.022}, abstractNote={Nanofibers were produced by electrospinning aqueous alkaline solutions containing different mass ratios of soy protein and lignin in the presence of poly(ethylene glycol) coadjutant, all of which presented shear thinning behavior. SEM revealed that the addition of polyethylene oxide as a coadjutant indeed facilitated the formation of defect-free fibers whose diameter increased with lignin concentration, in the range between ≈ 124 and ≈ 400 nm. Favorable interactions between lignin and soy protein were identified from data provided by differential scanning calorimetry. In addition, an increased hydrogen bonding and the loss of secondary structure of the proteins as the lignin concentration increased were observed from the disappearance of amide II (∼1500 cm−1) and III (∼1400–1200 cm−1) bands and a red shift of amide I band in the FT-IR spectrum. The unfolding of the protein contributed to a better interaction with lignin macromolecules, which further improved the electrospinning process. It is concluded that mixtures of lignin and soy proteins, two major renewable resources with interesting chemical features, are suitable for the development of composite sub-micron fibers.}, journal={REACTIVE & FUNCTIONAL POLYMERS}, author={Salas, Carlos and Ago, Mariko and Lucia, Lucian A. and Rojas, Orlando J.}, year={2014}, month={Dec}, pages={221–227} }
 @article{khakalo_filpponen_johansson_vishtal_lokanathan_rojas_laine_2014, title={Using gelatin protein to facilitate paper thermoformability}, volume={85}, ISSN={["1873-166X"]}, DOI={10.1016/j.reactfunctpolym.2014.09.024}, abstractNote={One of the main challenges of fiber-based packaging materials is the relatively poor elongation of cellulose under stress, which limits formability and molding in related products. Therefore, in this investigation we first used cellulose thin films and surface sensitive tools such as quartz crystal microbalance (QCM-D), surface plasmon resonance (SPR) and X-ray photoelectron spectroscopy (XPS) to evaluate the cellulose–gelatin interactions. It was found that the highest adsorption of gelatin onto cellulose occurred at the isoelectric pH of the protein. Based on this and other results, a gelatin loading is proposed to facilitate molecular and surface interactions and, thus to improve the formability of cellulose-based materials in paper molding. Aqueous gelatin solutions were sprayed on the surface of wet webs composed of softwood fibers and the chemical and mechanical changes that occurred were quantified. Upon gelatin treatment the elongation and tensile strength of paper under unrestrained drying was increased by ∼50% (from ∼10% to 14%) and by ∼30% (from 59 to 78 N m/g), respectively. The mechanical performance of gelatin-treated fibers was further improved by glutaraldehyde-assisted cross-linking. The proposed approach represents an inexpensive and facile method to improve the plasticity of fiber networks, which otherwise cannot be processed in the production of packaging materials by direct thermoforming.}, journal={REACTIVE & FUNCTIONAL POLYMERS}, author={Khakalo, Alexey and Filpponen, Ilari and Johansson, Leena-Sisko and Vishtal, Alexey and Lokanathan, Arcot R. and Rojas, Orlando J. and Laine, Janne}, year={2014}, month={Dec}, pages={175–184} }
 @article{park_hung_gan_rojas_lim_park_2013, title={Activated carbon from biochar: Influence of its physicochemical properties on the sorption characteristics of phenanthrene}, volume={149}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2013.09.085}, abstractNote={The relationship between physicochemical properties of biochar-based activated carbons and its adsorption was investigated using an aromatic model compound, phenanthrene. Solid-state 13C NMR analysis indicated more condensed aromatic structures when pyrolysis temperature increased or after activation process induced. The increasing aromaticity and non-protonated carbon fraction of the activated biochar treated at 300 °C amounted to 14.7% and 24.0%, respectively, compared to 7.4% and 4.4% for biochar treated at 700 °C. The surface area and pore volume were reduced with the increase in pyrolysis temperature, but increased after activation. Surface characteristics correlated with the initial sorption rate and equilibrium concentration of phenanthrene, but not with the aromaticity. Solid-state 2H NMR for phenanthrene-d10 saturated activated biochars, however, showed substantial difference in molecular mobility, which might be due to the high aromaticity of the activated biochars. Overall, these results provide an opportunity to manipulate the characteristics of biomass-based adsorbents based on the application needs.}, journal={BIORESOURCE TECHNOLOGY}, author={Park, Junyeong and Hung, Ivan and Gan, Zhehong and Rojas, Orlando J. and Lim, Kwang Hun and Park, Sunkyu}, year={2013}, month={Dec}, pages={383–389} }
 @article{zhang_carbonell_rojas_2013, title={Bioactive Cellulose Nanofibrils for Specific Human IgG Binding}, volume={14}, ISSN={["1526-4602"]}, DOI={10.1021/bm4007979}, abstractNote={Bioactive films were produced by conjugation of a short peptide onto modified cellulose nanofibrils (CNF). Specifically, a hydrophilic copolymer, poly(2-aminoethyl methacrylate hydrochloride-co-2-hydroxyethylmethacrylate) (poly(AMA-co-HEMA)), was grafted via surface initiated polymerization from an initiator coupled to CNF. The poly(AMA-co-HEMA) was used as a spacer and support layer for immobilization of the peptide, acetylated-HWRGWVA, which has specific affinity with human immunoglobulin G (hIgG). Two methods for peptide grafting were compared: modification of CNF in aqueous suspension followed by assembly into a bioactive film and peptide grafting on a preformed CNF film. The CNF-based networks were examined on solid supports via atomic force microscopy (AFM) and extreme resolution imaging with ultralow electron landing energies (scanning low energy electron microscopy). The specific binding capability of hIgG and nonspecific protein resistance of the resultant peptide-modified CNF were evaluated by using quartz crystal microgravimetry (QCM). The effects of initiator concentration and thickness of poly(AMA-co-HEMA) layer on hIgG adsorption were investigated in the developed systems, which exhibited high signal-to-noise response.}, number={12}, journal={BIOMACROMOLECULES}, author={Zhang, Yanxia and Carbonell, Ruben G. and Rojas, Orlando J.}, year={2013}, month={Dec}, pages={4161–4168} }
 @misc{hubbe_rojas_fingas_gupta_2013, title={Cellulosic substrates for removal of pollutants from aqueous systems: A review. 3. spilled oil and emulsified organic liquids}, volume={8}, DOI={10.15376/biores.8.2.3038-3097}, abstractNote={Water-insoluble oils, including crude petroleum and a wide variety of refined organic liquids, can cause major problems if spilled or leaked to aqueous environments. Potential environmental damage may be reduced if the spilled oil is promptly and efficiently removed from the water. This article reviews research that sheds light on the use of cellulose-based materials as sorbents to mitigate effects of oil spills. Encouraging results for oil sorption have been reported when using naturally hydrophobic cellulosic fibers such as unprocessed cotton, kapok, or milkweed seed hair. In addition, a wide assortment of cellulosic materials have been shown to be effective sorbents for hydrocarbon oils, especially in the absence of water, and their performance under water-wet conditions can be enhanced by various pretreatments that render them more hydrophobic. More research is needed on environmentally friendly systems to handle oil-contaminated sorbents after their use; promising approaches include their re-use after regeneration, anaerobic digestion, and incineration, among others. Research is also needed to further develop combined response systems in which biosorption is used along with other spill-response measures, including skimming, demulsification, biodegradation, and the use of booms to limit the spreading of oil slicks.}, number={2}, journal={BioResources}, author={Hubbe, M. A. and Rojas, O. J. and Fingas, M. and Gupta, B. S.}, year={2013}, pages={3038–1179} }
 @article{lokanathan_nykanen_seitsonen_johansson_campbell_rojas_ikkala_laine_2013, title={Cilia-Mimetic Hairy Surfaces Based on End-Immobilized Nanocellulose Colloidal Rods}, volume={14}, ISSN={["1526-4602"]}, DOI={10.1021/bm400633r}, abstractNote={We show a simple method toward nanoscale cilia-like structures, i.e., functional hairy surfaces, upon topochemically functionalizing nanorods of cellulose nanocrystals (CNCs) with thiol end groups (CNC-SHs), which leads to their immobilization onto a gold surface from one end, still allowing their orientational mobility. CNCs having a lateral dimension of 3-5 nm and length of 50-500 nm incorporate the native crystalline structure with hydrogen-bonded cellulose chains in the parallel configuration. This facilitates asymmetric, selective chemical modification of the reducing ends through reductive amination. Successful thiol functionalization is demonstrated using cryo transmission electron microscopy based on selective attachment of silver nanoparticles to the CNC-SH ends to form Janus-like colloidal rod-sphere adducts. The extent of thiol modification of CNC-SHs is quantified using X-ray photoelectron spectroscopy. The promoted binding of CNC-SHs on gold surfaces is shown by atomic force microscopy and quartz crystal microbalance, where the high dissipation suggests pronounced orientational mobility due to flexible joints at one rod end onto the surfaces. That the joints are flexible is also shown by the bending and realignment of the CNC-SH rods using a receding triple-phase evaporation front of a drying drop of water. The ability of the hairy surface to size-selectively resist particle binding was also investigated. As the CNCs are piezoelectric and allow magnetic functionalization by nanoparticles, we foresee a general platform for nanosized artificial cilia for fluid manipulation and controlled adsorption/desorption.}, number={8}, journal={BIOMACROMOLECULES}, author={Lokanathan, Arcot R. and Nykanen, Antti and Seitsonen, Jani and Johansson, Leena-Sisko and Campbell, Joseph and Rojas, Orlando J. and Ikkala, Olli and Laine, Janne}, year={2013}, month={Aug}, pages={2807–2813} }
 @article{carrillo_saloni_rojas_2013, title={Evaluation of O/W microemulsions to penetrate the capillary structure of woody biomass: interplay between composition and formulation in green processing}, volume={15}, ISSN={1463-9262 1463-9270}, url={http://dx.doi.org/10.1039/C3GC41325J}, DOI={10.1039/c3gc41325j}, abstractNote={The ability of microemulsions to overcome the complex capillary structure of wood is revealed in relation to its composition and formulation. The oil phase (limonene in this study) of O/W microemulsions is found to be critical for effective flooding. The type of amphiphile molecule used, including sodium lignosulfonate and alkyl polyglucosides as well as reference sodium dodecylsulfate and silicone-based surfactants, together with the viscosity of the resulting microemulsions were the main factors determining the dynamics and extent of fluid penetration. The associated observations were ascribed to the balance of the affinities of the surfactants for the substrate and its conductive elements. Owing to the inherent morphological and chemical features, large differences were observed as far as impregnation susceptibility of different wood types is concerned. By using appropriate surfactant mixtures it was possible for the microemulsions to penetrate the most recalcitrant woody biomass studied, with efficiencies up to 83% higher than that of water, at atmospheric pressure and room temperature. Application of microemulsions is a new alternative for green and efficient pre-treatment of woody biomass in biorefineries, to deliver (bio)chemical functions to the constrained spaces of the cell wall and to increase its accessibility.}, number={12}, journal={Green Chemistry}, publisher={Royal Society of Chemistry (RSC)}, author={Carrillo, Carlos A. and Saloni, Daniel and Rojas, Orlando J.}, year={2013}, pages={3377} }
 @article{goli_gera_liu_rao_rojas_genzer_2013, title={Generation and Properties of Antibacterial Coatings Based on Electrostatic Attachment of Silver Nanoparticles to Protein-Coated Polypropylene Fibers}, volume={5}, ISSN={["1944-8252"]}, DOI={10.1021/am4011644}, abstractNote={We present a simple method for attaching silver nanoparticles to polypropylene (PP) fibers in a two-step process to impart antibacterial properties. Specifically, PP fibers are pretreated by the adsorption from an aqueous solution of heat-denatured lysozyme (LYS) followed by LYS cross-linking using glutaraldehyde and sodium borohydride. At neutral pH, the surface of the adsorbed LYS layer is enriched with numerous positive charges. Silver nanoparticles (AgNPs) capped with trisodium citrate are subsequently deposited onto the protein-coated PP. Nanoparticle binding is mediated by electrostatic interactions between the positively charged LYS layer and the negatively charged AgNPs. The density of AgNPs deposited on PP depends on the amount of protein adsorbed on the surface. UV-vis spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy are employed to follow all preparation steps and to characterize the resulting functional surfaces. The antibacterial activity of the modified surfaces is tested against gram negative bacteria Escherichia coli (E. coli). Overall, our results show that PP surfaces coated with AgNPs exhibit excellent antibacterial activity with 100% removal efficiency.}, number={11}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Goli, Kiran K. and Gera, Nimish and Liu, Xiaomeng and Rao, Balaji M. and Rojas, Orlando J. and Genzer, Jan}, year={2013}, month={Jun}, pages={5298–5306} }
 @article{rahikainen_martin-sampedro_heikkinen_rovio_marjamaa_tamminen_rojas_kruus_2013, title={Inhibitory effect of lignin during cellulose bioconversion: The effect of lignin chemistry on non-productive enzyme adsorption}, volume={133}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2013.01.075}, abstractNote={The effect of lignin as an inhibitory biopolymer for the enzymatic hydrolysis of lignocellulosic biomass was studied; specially addressing the role of lignin in non-productive enzyme adsorption. Botanical origin and biomass pre-treatment give rise to differences in lignin structure and the effect of these differences on enzyme binding and inhibition were elucidated. Lignin was isolated from steam explosion (SE) pre-treated and non-treated spruce and wheat straw and used for the preparation of ultrathin films for enzyme binding studies. Binding of Trichoderma reesei Cel7A (CBHI) and the corresponding Cel7A-core, lacking the linker and the cellulose-binding domain, to the lignin films was monitored using a quartz crystal microbalance (QCM). SE pre-treatment altered the lignin structure, leading to increased enzyme adsorption. Thus, the positive effect of SE pre-treatment, opening the cell wall matrix to make polysaccharides more accessible, may be compromised by the structural changes of lignin that increase non-productive enzyme adsorption.}, journal={BIORESOURCE TECHNOLOGY}, author={Rahikainen, Jenni L. and Martin-Sampedro, Raquel and Heikkinen, Harri and Rovio, Stella and Marjamaa, Kaisa and Tamminen, Tarja and Rojas, Orlando J. and Kruus, Kristiina}, year={2013}, month={Apr}, pages={270–278} }
 @article{garcia-ubasart_vidal_torres_rojas_2013, title={Laccase-Mediated Coupling of Nonpolar Chains for the Hydrophobization of Lignocellulose}, volume={14}, ISSN={["1525-7797"]}, DOI={10.1021/bm400291s}, abstractNote={We investigate the use of laccase enzymes to couple short nonpolar chains containing aromatic groups onto flax fibers and nanofibrillated cellulose (NFC) with different lignin contents. Trametes villosa , Pycnoporus cinnabarinus , and Myceliophthora thermophila were used to facilitate surface coupling and to produce materials with different levels of hydrophobicity. Heat treatment of fiber webs after lacccase-mediated coupling markedly increased the resistance to water absorption. The highest hydrophobization levels of flax fibers was achieved by coupling dodecyl 3,4,5-trihydroxybenzoate (HB-C12), which yielded water contact angles (WCAs) of 80-96 degrees and water absorption times (drop tests) of ca. 73 min. The results from apparent aromatic content and FTIR analyses confirmed the laccase-mediated coupling of HB-C12 onto the cellulose fibers. Ultrathin films of NFC were also used as substrates for enzyme-mediated hydrophobization with HB-C12. In these cases, WCAs in the range of 87-104 degrees were achieved, depending on the conditions. Quartz crystal microgravimetry (QCM) was used to study the dynamics and the extent of the coupling process onto cellulose. The results help to better understand the mechanisms involved in laccase-mediated hydrophobization and provide a proof of a biotechnological platform for the development of value-added fiber products.}, number={5}, journal={BIOMACROMOLECULES}, author={Garcia-Ubasart, Jordi and Vidal, Teresa and Torres, Antonio L. and Rojas, Orlando J.}, year={2013}, month={May}, pages={1637–1644} }
 @article{hoeger_nair_ragauskas_deng_rojas_zhu_2013, title={Mechanical deconstruction of lignocellulose cell walls and their enzymatic saccharification}, volume={20}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-013-9867-9}, number={2}, journal={CELLULOSE}, author={Hoeger, Ingrid C. and Nair, Sandeep S. and Ragauskas, Arthur J. and Deng, Yulin and Rojas, Orlando J. and Zhu, J. Y.}, year={2013}, month={Apr}, pages={807–818} }
 @article{salas_rojas_lucia_hubbe_genzer_2013, title={On the Surface Interactions of Proteins with Lignin}, volume={5}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/am3024788}, DOI={10.1021/am3024788}, abstractNote={Lignins are used often in formulations involving proteins but little is known about the surface interactions between these important biomacromolecules. In this work, we investigate the interactions at the solid-liquid interface of lignin with the two main proteins in soy, glycinin (11S) and β-conglycinin (7S). The extent of adsorption of 11S and 7S onto lignin films and the degree of hydration of the interfacial layers is quantified via Quartz crystal microgravimetry (QCM) and surface plasmon resonance (SPR). Solution ionic strength and protein denaturation (2-mercaptoethanol and urea) critically affect the adsorption process as protein molecules undergo conformational changes and their hydrophobic or hydrophilic amino acid residues interact with the surrounding medium. In general, the adsorption of the undenatured proteins onto lignin is more extensive compared to that of the denatured biomolecules and a large amount of water is coupled to the adsorbed molecules. The reduction in water contact angle after protein adsorption (by ~40° and 35° for undenatured 11S and 7S, respectively) is explained by strong nonspecific interactions between soy proteins and lignin.}, number={1}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Salas, Carlos and Rojas, Orlando J. and Lucia, Lucian A. and Hubbe, Martin A. and Genzer, Jan}, year={2013}, month={Jan}, pages={199–206} }
 @article{martin-sampedro_rahikainen_johansson_marjamaa_laine_kruus_rojas_2013, title={Preferential Adsorption and Activity of Monocomponent Cellulases on Lignocellulose Thin Films with Varying Lignin Content}, volume={14}, ISSN={["1526-4602"]}, DOI={10.1021/bm400230s}, abstractNote={Understanding the enzymatic hydrolysis of cellulose and the influence of lignin in the process are critical for viable production of fuels and chemicals from lignocellulosic biomass. The interactions of monocomponent cellulases with cellulose and lignin substrates were investigated by using thin films supported on quartz crystal microgravimetry (QCM) resonators. Trichoderma reesei exoglucanase (CBH-I) and endoglucanase (EG-I) bound strongly to both cellulose and lignin but EG-I exhibited a distinctive higher affinity with lignin, causing a more extensive inhibition of the cellulolytic reactions. CBH-I was found to penetrate into the bulk of the cellulose substrate increasing the extent of hydrolysis and film deconstruction. In the absence of a cellulose binding domain (CBD) and a linker, the CBH-I core adsorbed slowly and was not able to penetrate into the film. Conversely to CBH-I, EG-I exhibited activity only on the surface of the lignocellulose substrate even when containing a CBD and a linker. Interestingly, EG-I displayed a clearly different interaction profile as a function of contact time registered by QCM.}, number={4}, journal={BIOMACROMOLECULES}, author={Martin-Sampedro, Raquel and Rahikainen, Jenni L. and Johansson, Leena-Sisko and Marjamaa, Kaisa and Laine, Janne and Kruus, Kristiina and Rojas, Orlando J.}, year={2013}, month={Apr}, pages={1231–1239} }
 @article{taajamaa_rojas_laine_yliniemi_kontturi_2013, title={Protein-assisted 2D assembly of gold nanoparticles on a polysaccharide surface}, volume={49}, ISSN={["1364-548X"]}, DOI={10.1039/c2cc37288f}, abstractNote={Site-specific assembly of gold nanoparticles on a polysaccharide surface was accomplished via a straightforward method exploiting interfacial polymer blends, selective protein adsorption and electrostatic interaction. The method could be useful in further applications due to the universal nature of the utilized phenomena.}, number={13}, journal={CHEMICAL COMMUNICATIONS}, author={Taajamaa, Laura and Rojas, Orlando J. and Laine, Janne and Yliniemi, Kirsi and Kontturi, Eero}, year={2013}, pages={1318–1320} }
 @article{arboleda_hughes_lucia_laine_ekman_rojas_2013, title={Soy protein-nanocellulose composite aerogels}, volume={20}, ISSN={["0969-0239"]}, DOI={10.1007/s10570-013-9993-4}, number={5}, journal={CELLULOSE}, author={Arboleda, Julio C. and Hughes, Mark and Lucia, Lucian A. and Laine, Janne and Ekman, Kalle and Rojas, Orlando J.}, year={2013}, month={Oct}, pages={2417–2426} }
 @article{zhang_islam_carbonell_rojas_2013, title={Specific Binding of Immunoglobulin G with Bioactive Short Peptides Supported on Antifouling Copolymer Layers for Detection in Quartz Crystal Microgravimetry and Surface Plasmon Resonance}, volume={85}, ISSN={["1520-6882"]}, DOI={10.1021/ac302874s}, abstractNote={A new peptide-based system supported on copolymer brushes grafted from gold sensors and with resistance to nonspecific adsorption is reported for selective binding of human immunoglobulin G (IgG). A random copolymer rich in primary amines, poly(2-aminoethyl methacrylate hydrochloride-co-2-hydroxyethyl methacrylate) (poly(AMA-co-HEMA)) was first grafted from initiator-coated gold substrates via activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP), followed by immobilization of acetylated-HWRGWVA peptide, which has specific binding affinity with IgG. The peptide ligands covalently linked to the soft copolymer layer were characterized by X-ray photoelectron spectroscopy (XPS), water contact angle, ellipsometry, and atomic force microscopy (AFM). The extent of binding, binding affinity, and selectivity for target IgG molecules as well as the capability to minimize nonspecific interactions with other proteins were examined by fluorescence imaging, surface plasmon resonance (SPR), and quartz crystal microgravimetry (QCM). The effect of copolymer molecular composition and analyte concentration was elucidated in order to design systems based on immobilized peptides for high signal-to-noise response and detection limits that meet the requirements for IgG biosensing in fluid matrixes.}, number={2}, journal={ANALYTICAL CHEMISTRY}, author={Zhang, Yanxia and Islam, Nafisa and Carbonell, Ruben G. and Rojas, Orlando J.}, year={2013}, month={Jan}, pages={1106–1113} }
 @article{zhang_islam_carbonell_rojas_2013, title={Specificity and Regenerability of Short Peptide Ligands Supported on Polymer Layers for Immunoglobulin G Binding and Detection}, volume={5}, ISSN={["1944-8244"]}, DOI={10.1021/am4021186}, abstractNote={We demonstrate the specificity, regenerability, and excellent storage stability of short peptide-based systems for detection of immunoglobulin G (IgG). The bioactive component consisted of acetylated-HWRGWVA (Ac-HWRGWVA), a peptide with high IgG binding affinity, which was immobilized onto copolymer matrixes of poly(2-aminoethyl methacrylate hydrochloride-co-2-hydroxyethyl methacrylate) (poly(AMA-co-HEMA)). Surface plasmon resonance (SPR) and quartz crystal microgravimetry (QCM) were utilized with other complementary techniques to systematically investigate interfacial activities, mainly IgG binding performance as a function of the graft density and degree of polymerization of the poly(AMA-co-HEMA) support layer. Results from sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorescence microscopy indicate that the bioactive system is highly specific to IgG and resistant to nonspecific interactions when tested in mixed protein solutions.}, number={16}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Zhang, Yanxia and Islam, Nafisa and Carbonell, Ruben G. and Rojas, Orlando J.}, year={2013}, month={Aug}, pages={8030–8037} }
 @article{rojas_lokanathan_kontturi_laine_bock_2013, title={The unusual interactions between polymer grafted cellulose nanocrystal aggregates}, volume={9}, ISSN={["1744-683X"]}, DOI={10.1039/c3sm51494c}, abstractNote={Using computer simulations we study how a corona of polymer molecules grafted to cellulose nanocrystal aggregate (CNA) particles influences the interaction between pairs of parallel CNAs. The resulting distance and orientation (face-to-face versus edge-to-edge) dependence is very rich and counterintuitive. Although the unperturbed polymer corona assumes cylindrical symmetry relatively quickly as the degree of polymerisation increases, the polymer mediated interactions between the grafted particles are strongly orientation dependent. Rather unexpectedly we find that the forces in the face-to-face orientation are much larger than in the edge-to-edge configuration although in the latter case the distance between the particle surfaces is much smaller. The reason for this effect is that overall the face-to-face orientation leads to larger chain confinement. Interestingly, we find that the deviations of the polymer mediated interactions from cylindrical symmetry are larger in the case of longer grafted molecules compared to shorter ones. When the distance between the CNAs becomes larger and the overlap of the polymer coronas becomes small, the orientation dependence of the mediated interaction vanishes and the particles behave as cylindrical rods. However, this is only a crossover point where the behaviour of the system inverts to slightly larger forces in the edge-to-edge compared to the face-to-face configuration. Thus, even though the polymer density around the CNAs is nearly perfectly cylindrically symmetric the polymer mediated interactions are strongly orientation dependent, revealing the polygon character of the CNA cross-section.}, number={37}, journal={SOFT MATTER}, author={Rojas, Orlando J. and Lokanathan, Arcot R. and Kontturi, Eero and Laine, Janne and Bock, Henry}, year={2013}, pages={8965–8973} }
 @article{ago_jakes_rojas_2013, title={Thermomechanical Properties of Lignin-Based Electrospun Nanofibers and Films Reinforced with Cellulose Nanocrystals: A Dynamic Mechanical and Nanoindentation Study}, volume={5}, ISSN={["1944-8252"]}, DOI={10.1021/am403451w}, abstractNote={We produced defect-free electrospun fibers from aqueous dispersions of lignin, poly(vinyl alcohol) (PVA), and cellulose nanocrystals (CNCs), which were used as reinforcing nanoparticles. The thermomechanical performance of the lignin-based electrospun fibers and the spin-coated thin films was improved when they were embedded with CNCs. Isochronal dynamic mechanical analysis (DMA) was used to assess the viscoelastic properties of the lignin:PVA electrospun fiber mats loaded with CNCs. DMA revealed that α relaxation processes became less prominent with an increased lignin content, an effect that correlated with the loss tangent (tan δ = E″/E') and α peak (Tg) that shifted to higher temperatures. This can be ascribed to the restraint of the segmental motion of PVA in the amorphous regions caused by strong intermolecular interactions. The reinforcing effect and high humidity stability attained by addition of CNCs (5, 10, or 15 wt %) in the multicomponent fiber mats were revealed. Nanoindentation was performed to assess the elastic modulus and hardness of as-prepared and cross-section surfaces of spin-coated lignin:PVA (75:25) films loaded with CNC. The properties of the two surfaces differed, and only the trend in cross-section elastic modulus correlated with DMA results. After addition of 5 wt % CNCs, both the DMA and nanoindentation elastic modulus remained constant, while after addition of 15 wt % CNCs, both increased substantially. An indentation size effect was observed in the nanoindentation hardness, and the results provided insight into the effect of addition of CNCs on the microphysical processes controlling the yield behavior in the composites.}, number={22}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Ago, Mariko and Jakes, Joseph E. and Rojas, Orlando J.}, year={2013}, month={Nov}, pages={11768–11776} }
 @article{park_meng_lim_rojas_park_2013, title={Transformation of lignocellulosic biomass during torrefaction}, volume={100}, ISSN={["0165-2370"]}, DOI={10.1016/j.jaap.2012.12.024}, abstractNote={In this study, the effect of torrefaction on the chemical and structural transformation of lignocellulosic biomass was investigated using complementary analytical tools. It was observed that the acid-insoluble fraction was increased from approximately 30 to 38% and the methoxyl content was decreased to about half after torrefaction at 330 °C for 2.5 min. These results highlight the formation of condensed structures along with lignin transformation via demethoxylation. Solid-state NMR spectroscopy indicated that upon torrefaction the aromaticity increased from about 36 to 60%. For the sample torrefied at 330 °C, the non-protonated aromatic carbon fraction was found to be about 60% of total aromatic carbons, indicating the formation of large aromatic clusters. The complementary analyses used in this study are proposed as a suitable approach for the elucidation of chemical and structural transformation of biomass during thermal treatment.}, journal={JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS}, author={Park, Junyeong and Meng, Jiajia and Lim, Kwang Hun and Rojas, Orlando J. and Park, Sunkyu}, year={2013}, month={Mar}, pages={199–206} }
 @article{salas_genzer_lucia_hubbe_rojas_2013, title={Water-Wettable Polypropylene Fibers by Facile Surface Treatment Based on Soy Proteins}, volume={5}, ISSN={["1944-8252"]}, DOI={10.1021/am401065t}, abstractNote={Modification of the wetting behavior of hydrophobic surfaces is essential in a variety of materials, including textiles and membranes that require control of fluid interactions, adhesion, transport processes, sensing, etc. This investigation examines the enhancement of wettability of an important class of textile materials, viz., polypropylene (PP) fibers, by surface adsorption of different proteins from soybeans, including soy flour, isolate,glycinin, and β-conglycinin. Detailed investigations of soy adsorption from aqueous solution (pH 7.4, 25 °C) on polypropylene thin films is carried out using quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). A significant amount of protein adsorbs onto the PP surfaces primarily due to hydrophobic interactions. We establish that adsorption of a cationic surfactant, dioctadecyldimethylammonium bromide (DODA) onto PP surfaces prior to the protein deposition dramatically enhances its adsorption. The adsorption of proteins from native (PBS buffer, pH 7.4, 25 °C) and denatured conditions (PBS buffer, pH 7.4, 95 °C) onto DODA-treated PP leads to a high coverage of the proteins on the PP surface as confirmed by a significant improvement in water wettability. A shift in the contact angle from 128° to completely wettable surfaces (≈0°) is observed and confirmed by imaging experiments conducted with fluorescence tags. Furthermore, the results from wicking tests indicate that hydrophobic PP nonwovens absorb a significant amount of water after protein treatment, i.e., the PP-modified surfaces become completely hydrophilic.}, number={14}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Salas, Carlos and Genzer, Jan and Lucia, Lucian A. and Hubbe, Martin A. and Rojas, Orlando J.}, year={2013}, month={Jul}, pages={6541–6548} }
 @article{salas_rojas_lucia_hubbe_genzer_2012, title={Adsorption of Glycinin and beta-Conglycinin on Silica and Cellulose: Surface Interactions as a Function of Denaturation, pH, and Electrolytes}, volume={13}, ISSN={["1526-4602"]}, DOI={10.1021/bm2014153}, abstractNote={Soybean proteins have found uses in different nonfood applications due to their interesting properties. We report on the kinetics and extent of adsorption on silica and cellulose surfaces of glycinin and β-conglycinin, the main proteins present in soy. Quartz crystal microgravimetry (QCM) experiments indicate that soy protein adsorption is strongly affected by changes in the physicochemical environment. The affinity of glycinin and the mass adsorbed on silica and cellulose increases (by ca. 13 and 89%, respectively) with solution ionic strength (as it increases from 0 to 100 mM NaCl) due to screening of electrostatic interactions. In contrast, β-conglycinin adsorbs on the same substrates to a lower extent and the addition of electrolyte reduces adsorption (by 25 and 57%, respectively). The addition of 10 mM 2-mercaptoethanol, a denaturing agent, reduces the adsorption of both proteins with a significant effect for glycinin. This observation is explained by the cleavage of disulfide bonds which allows unfolding of the molecules and promotes dissociation into subunits that favors more compact adsorbed layer structures. In addition, adsorption of glycinin onto cellulose decreases with lowering the pH from neutral to pH 3 due to dissociation of the macromolecules, resulting in flatter adsorbed layers. The respective adsorption isotherms fit a Langmuir model and QCM shifts in energy dissipation and frequency reveal multiple-step kinetic processes indicative of changes in adlayer structure.}, number={2}, journal={BIOMACROMOLECULES}, author={Salas, Carlos and Rojas, Orlando J. and Lucia, Lucian A. and Hubbe, Martin A. and Genzer, Jan}, year={2012}, month={Feb}, pages={387–396} }
 @article{vallejos_peresin_rojas_2012, title={All-Cellulose Composite Fibers Obtained by Electrospinning Dispersions of Cellulose Acetate and Cellulose Nanocrystals}, volume={20}, ISSN={["1572-8919"]}, DOI={10.1007/s10924-012-0499-1}, abstractNote={All-cellulose composite fibers were produced by electrospinning dispersions containing cellulose acetate (CA) and cellulose nanocrystals (CNCs). Precursor polymer matrices were obtained after dispersion of CA with different degrees of substitution in a binary mixture of organic solvents. The obtained fibers of CA loaded with CNCs had typical widths in the nano- and micro-scale and presented a glass transition temperature of 145 °C. The CA component was converted to cellulose by using alkaline hydrolysis to yield all-cellulose composite fibers that preserved the original morphology of the precursor system. Together with Fourier Transform Infrared Spectroscopy fingerprints the thermal behavior of the all-cellulose composite fibers indicated complete conversion of cellulose acetate to regenerated cellulose. Noticeable changes in the thermal, surface and chemical properties were observed upon deacetylation. Not only the thermal transitions of cellulose acetate disappeared but the initial water contact angle of the web was reduced drastically. Overall, we propose a simple method to produce all-cellulose composite fibers which are expected to display improved thermo-mechanical properties while keeping the unique features of the cellulose polymer.}, number={4}, journal={JOURNAL OF POLYMERS AND THE ENVIRONMENT}, author={Vallejos, Maria E. and Peresin, Maria S. and Rojas, Orlando J.}, year={2012}, month={Dec}, pages={1075–1083} }
 @article{hoeger_filpponen_martin-sampedro_johansson_osterberg_laine_kelley_rojas_2012, title={Bicomponent Lignocellulose Thin Films to Study the Role of Surface Lignin in Cellulolytic Reactions}, volume={13}, ISSN={["1526-4602"]}, DOI={10.1021/bm301001q}, abstractNote={Ultrathin bicomponent films of cellulose and lignin derivatives were deposited on silica supports by spin coating, and after conversion into the respective polymer precursor, they were used as a model system to investigate interfacial phenomena relevant to lignocellulose biocatalysis. Film morphology, surface chemical composition, and wettability were determined by atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle, respectively. Phase separation of cellulose and lignin produced structures that resembled the cell wall of fibers and were used to monitor enzyme binding and cellulolytic reactions via quartz crystal microgravimetry. The rate and extent of hydrolysis was quantified by using kinetic models that indicated the role of the surface lignin domains in enzyme inhibition. Hydrophobic interactions between cellulases and the substrates and their critical role on irreversible adsorption were elucidated by using acetylated lignin films with different degrees of substitution. Overall, it is concluded that sensors based on the proposed ultrathin films of lignocellulose can facilitate a better understanding of the complex events that occur during bioconversion of cellulosic biomass.}, number={10}, journal={BIOMACROMOLECULES}, author={Hoeger, Ingrid C. and Filpponen, Ilari and Martin-Sampedro, Raquel and Johansson, Leena-Sisko and Osterberg, Monika and Laine, Janne and Kelley, Stephen and Rojas, Orlando J.}, year={2012}, month={Oct}, pages={3228–3240} }
 @article{taajamaa_kontturi_laine_rojas_2012, title={Bicomponent fibre mats with adhesive ultra-hydrophobicity tailored with cellulose derivatives}, volume={22}, ISSN={["1364-5501"]}, DOI={10.1039/c2jm30572k}, abstractNote={Morphologies featured in bicomponent 2D ultrathin films were reproduced on 3D non-woven microfibre structures. Fibre networks were constructed by electrospinning hydrophobised cellulose derivatives, trimethylsilyl cellulose (TMSC) and cellulose triacetate (CTA), dissolved in a common solvent. Diverse morphologies were obtained depending on the polymer blend ratio: electrospinning of TMSC produced non-continuous micron fibres with shallow dints, TMSC/CTA 5 : 1 flat micron fibres with regular pore arrays, TMSC/CTA 1 : 1 wrinkled micron fibres decorated with shallow dints and occasional larger pores, TMSC/CTA 1 : 5 flat micron fibres with ellipsoidal porous structures and finally, CTA that led to smooth micron and submicron fibres. The fibre mats were ultra-hydrophobic with characteristic water contact angles of ca. 150 degrees. In addition, they were characterised by high contact angle hysteresis, and water droplets adhered to the substrate even after tilting the system upside down. Through conversion of the respective components to cellulose, chemical and adsorption properties of the fibre networks could be tuned without significantly altering the large-scale network morphology.}, number={24}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Taajamaa, Laura and Kontturi, Eero and Laine, Janne and Rojas, Orlando J.}, year={2012}, pages={12072–12082} }
 @article{li_rojas_hinestroza_2012, title={Boundary Lubrication of PEO-PPO-PEO Triblock Copolymer Physisorbed on Polypropylene, Polyethylene, and Cellulose Surfaces}, volume={51}, ISSN={["0888-5885"]}, DOI={10.1021/ie202292r}, abstractNote={In situ lateral force microscopy (LFM) and X-ray photoelectron spectroscopy (XPS) were used to probe the lubrication behavior of an aqueous solution of poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) (PEO-PPO-PEO) symmetric triblock copolymer on thin films of polypropylene (PP), polyethylene (PE), and cellulose. LFM experiments were carried out while the substrates were immersed in water and in solutions of the copolymer. The friction coefficient on PP and PE was reduced after adsorption from the PEO-PPO-PEO aqueous solution while the opposite effect was observed for cellulose surfaces. A critical normal loading force, at which the friction coefficient of the lubricated and unlubricated surfaces is equal, was identified and related to the affinity of the polymer with the substrate. Further experiments were performed to mimic practical operations involving lubricant addition during manufacturing and postprocessing removal. XPS was used to verify the presence of the lubricant on the polymeric substra...}, number={7}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Li, Y. and Rojas, O. J. and Hinestroza, J. P.}, year={2012}, month={Feb}, pages={2931–2940} }
 @article{carrillo_saloni_lucia_hubbe_rojas_2012, title={Capillary flooding of wood with microemulsions from Winsor I systems}, volume={381}, ISSN={["0021-9797"]}, DOI={10.1016/j.jcis.2012.05.032}, abstractNote={A new approach based on microemulsions formulated with at least 85% water and minority components consisting of oil (limonene) and surfactant (anionic and nonionic) is demonstrated for the first time to be effective for flooding wood’s complex capillary structure. The formulation of the microemulsion was based on phase behavior scans of Surfactant–Oil–Water systems (SOWs) and the construction of pseudo-ternary diagrams to localize thermodynamically stable one-phase emulsion systems with different composition, salinity and water-to-oil ratios. Wicking and fluid penetration isotherms followed different kinetic regimes and indicated enhanced performance relative to that of the base fluids (water, oil or surfactant solutions). The key properties of microemulsions to effectively penetrate the solid structure are discussed; microemulsion formulation and resultant viscosity are found to have a determining effect in the extent of fluid uptake. The solubilization of cell wall components is observed after microemulsion impregnation. Thus, the microemulsion can be tuned not only to effectively penetrate the void spaces but also to solubilize hydrophobic and hydrophilic components. The concept proposed in this research is expected to open opportunities in fluid sorption in fiber systems for biomass pretreatment, and delivery of hydrophilic or lipophilic moieties in porous, lignocellulosics.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Carrillo, Carlos A. and Saloni, Daniel and Lucia, Lucian A. and Hubbe, Martin A. and Rojas, Orlando J.}, year={2012}, month={Sep}, pages={171–179} }
 @article{ferrer_quintana_filpponen_solala_vidal_rodriguez_laine_rojas_2012, title={Effect of residual lignin and heteropolysaccharides in nanofibrillar cellulose and nanopaper from wood fibers}, volume={19}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-012-9788-z}, number={6}, journal={CELLULOSE}, author={Ferrer, Ana and Quintana, Elisabet and Filpponen, Ilari and Solala, Iina and Vidal, Teresa and Rodriguez, Alejandro and Laine, Janne and Rojas, Orlando J.}, year={2012}, month={Dec}, pages={2179–2193} }
 @article{goli_rojas_oezcam_genzer_2012, title={Generation of Functional Coatings on Hydrophobic Surfaces through Deposition of Denatured Proteins Followed by Grafting from Polymerization}, volume={13}, ISSN={["1525-7797"]}, DOI={10.1021/bm300075u}, abstractNote={Hydrophilic coatings were produced on flat hydrophobic substrates featuring n-octadecyltrichlorosilane (ODTS) and synthetic polypropylene (PP) nonwoven surfaces through the adsorption of denatured proteins. Specifically, physisorption from aqueous solutions of α-lactalbumin, lysozyme, fibrinogen, and two soy globulin proteins (glycinin and β-conglycinin) after chemical (urea) and thermal denaturation endowed the hydrophobic surfaces with amino and hydroxyl functionalities, yielding enhanced wettability. Proteins adsorbed strongly onto ODTS and PP through nonspecific interactions. The thickness of adsorbed heat-denatured proteins was adjusted by varying the pH, protein concentration in solution, and adsorption time. In addition, the stability of the immobilized protein layer was improved significantly after interfacial cross-linking with glutaraldehyde in the presence of sodium borohydride. The amino and hydroxyl groups present on the protein-modified surfaces served as reactive sites for the attachment of polymerization initiators from which polymer brushes were grown by surface-initiated atom-transfer radical polymerization of 2-hydroxyethyl methacrylate. Protein denaturation and adsorption as well as the grafting of polymeric brushes were characterized by circular dichroism, ellipsometry, contact angle, and Fourier transform infrared spectroscopy in the attenuated total reflection mode.}, number={5}, journal={BIOMACROMOLECULES}, author={Goli, Kiran K. and Rojas, Orlando J. and Oezcam, A. Evren and Genzer, Jan}, year={2012}, month={May}, pages={1371–1382} }
 @article{orelma_johansson_filpponen_rojas_laine_2012, title={Generic Method for Attaching Biomolecules via Avidin-Biotin Complexes Immobilized on Films of Regenerated and Nanofibrillar Cellulose}, volume={13}, ISSN={["1526-4602"]}, DOI={10.1021/bm300781k}, abstractNote={We investigated the adsorption and chemical conjugation of avidin and its deglycosylated form, neutravidin, on films of regenerated and nanofibrillar cellulose. The dynamics and extent of biomolecular attachment were monitored in situ by quartz crystal microbalance microgravimetry and ex situ via surface analyses with atomic force microscopy and X-ray photoelectron spectroscopy. The installation of carboxyl groups on cellulose after modification with carboxymethylated cellulose (CMC) or TEMPO-oxidation significantly increases physisorption of avidins, which can be then covalently conjugated by using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride/N-hydroxysuccinimide (EDS/NHS) coupling chemistries. The developed cellulose-avidin biointerfaces are able to scavenge biotinylated molecules from solution as demonstrated by successful surface complexation of biotinylated bovine serum albumin (Biotin-BSA) and antihuman immunoglobulin G (Biotin-anti-hIgG). Finally, we show that cellulose substrates carrying immobilized anti-hIgG are effective in detecting human immunoglobulin G (hIgG) from fluid matrices.}, number={9}, journal={BIOMACROMOLECULES}, author={Orelma, Hannes and Johansson, Leena-sisko and Filpponen, Ilari and Rojas, Orlando J. and Laine, Janne}, year={2012}, month={Sep}, pages={2802–2810} }
 @article{ago_okajima_jakes_park_rojas_2012, title={Lignin-Based Electrospun Nanofibers Reinforced with Cellulose Nanocrystals}, volume={13}, ISSN={["1526-4602"]}, DOI={10.1021/bm201828g}, abstractNote={Lignin-based fibers were produced by electrospinning aqueous dispersions of lignin, poly(vinyl alcohol) (PVA), and cellulose nanocrystals (CNCs). Defect-free nanofibers with up to 90 wt % lignin and 15% CNCs were achieved. The properties of the aqueous dispersions, including viscosity, electrical conductivity, and surface tension, were examined and correlated to the electrospinnability and resulting morphology of the composite fibers. A ternary lignin-PVA-water phase diagram was constructed as a tool to rationalize the effect of mixing ratios on the dispersion electrospinability and morphology of the resulting fibers. The influence of reinforcing CNCs on the thermal properties of the multicomponent fibers was investigated by using thermal gravimetric analysis and differential scanning calorimetry. The thermal stability of the system was observed to increase owing to a strong interaction of the lignin-PVA matrix with the dispersed CNCs, mainly via hydrogen bonding, as observed in Fourier transform infrared spectroscopy experiments.}, number={3}, journal={BIOMACROMOLECULES}, author={Ago, Mariko and Okajima, Kunihiko and Jakes, Joseph E. and Park, Sunkyu and Rojas, Orlando J.}, year={2012}, month={Mar}, pages={918–926} }
 @article{liu_li_krause_pasquinelli_rojas_2012, title={Mesoscopic Simulations of the Phase Behavior of Aqueous EO19PO29EO19 Solutions Confined and Sheared by Hydrophobic and Hydrophilic Surfaces}, volume={4}, ISSN={["1944-8252"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863067883&partnerID=MN8TOARS}, DOI={10.1021/am200917h}, abstractNote={The MesoDyn method is used to investigate associative structures in aqueous solution of a nonionic triblock copolymer consisting of poly(propylene oxide) capped on both ends with poly(ethylene oxide) chains. The effect of adsorbing (hydrophobic) and nonadsorbing (hydrophilic) solid surfaces in contact with aqueous solutions of the polymer is elucidated. The macromolecules form self-assembled structures in solution. Confinement under shear forces is investigated in terms of interfacial behavior and association. The formation of micelles under confinement between hydrophilic surfaces occurs faster than in bulk aqueous solution while layered structures assemble when the polymers are confined between hydrophobic surfaces. Micelles are deformed under shear rates of 1 μs(-1) and eventually break to form persistent, adsorbed layered structures. As a result, surface damage under frictional forces is prevented. Overall, this study indicates that aqueous triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) (Pluronics, EO(m)PO(n)EO(m)) act as a boundary lubricant for hydrophobic surfaces but not for hydrophilic ones.}, number={1}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Liu, Hongyi and Li, Yan and Krause, Wendy E. and Pasquinelli, Melissa A. and Rojas, Orlando J.}, year={2012}, month={Jan}, pages={87–95} }
 @article{payne_jackson_aizpurua_rojas_hubbe_2012, title={Oil Spills Abatement: Factors Affecting Oil Uptake by Cellulosic Fibers}, volume={46}, ISSN={["1520-5851"]}, DOI={10.1021/es3015524}, abstractNote={Wood-derived cellulosic fibers prepared in different ways were successfully employed to absorb simulated crude oil, demonstrating their possible use as absorbents in the case of oil spills. When dry fibers were used, the highest sorption capacity (six parts of oil per unit mass of fiber) was shown by bleached softwood kraft fibers, compared to hardwood bleached kraft and softwood chemithermomechanical pulp(CTMP) fibers. Increased refining of CTMP fibers decreased their oil uptake capacity. When the fibers were soaked in water before exposure to the oil, the ability of the unmodified kraft fibers to sorb oil was markedly reduced, whereas the wet CTMP fibers were generally more effective than the wet kraft fibers. Predeposition of lignin onto the surfaces of the bleached kraft fibers improved their ability to take up oil when wet. Superior ability to sorb oil in the wet state was achieved by pretreating the kraft fibers with a hydrophobic sizing agent, alkenylsuccinic anhydride (ASA). Contact angle tests on a model cellulose surface showed that some of the sorption results onto wetted fibers could be attributed to the more hydrophobic nature of the fibers after treatment with either lignin or ASA.}, number={14}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Payne, Katharine C. and Jackson, Colby D. and Aizpurua, Carlos E. and Rojas, Orlando J. and Hubbe, Martin A.}, year={2012}, month={Jul}, pages={7725–7730} }
 @article{zoppe_venditti_rojas_2012, title={Pickering emulsions stabilized by cellulose nanocrystals grafted with thermo-responsive polymer brushes}, volume={369}, ISSN={0021-9797}, url={http://dx.doi.org/10.1016/j.jcis.2011.12.011}, DOI={10.1016/j.jcis.2011.12.011}, abstractNote={Cellulose nanocrystals (CNCs) from ramie fibers are studied as stabilizers of oil-in-water emulsions. The phase behavior of heptane and water systems is studied, and emulsions stabilized by CNCs are analyzed by using drop sizing (light scattering) and optical, scanning, and freeze-fracture electron microscopies. Water-continuous Pickering emulsions are produced with cellulose nanocrystals (0.05-0.5 wt%) grafted with thermo-responsive poly(NIPAM) brushes (poly(NIPAM)-g-CNCs). They are observed to be stable during the time of observation of 4 months. In contrast, unmodified CNCs are unable to stabilize heptane-in-water emulsions. After emulsification, poly(NIPAM)-g-CNCs are observed to form aligned, layered structures at the oil-water interface. The emulsions stabilized by poly(NIPAM)-g-CNCs break after heating at a temperature above the LCST of poly(NIPAM), which is taken as indication of the temperature responsiveness of the brushes installed on the particles and thus the responsiveness of the Pickering emulsions. This phenomenon is further elucidated via rheological measurements, in which viscosities of the Pickering emulsions increase on approach of the low critical solution temperature of poly(NIPAM). The effect of temperature can be counterbalanced with the addition of salt which is explained by the reduction of electrostatic and steric interactions of poly(NIPAM)-g-CNCs at the oil-water interface.}, number={1}, journal={Journal of Colloid and Interface Science}, publisher={Elsevier BV}, author={Zoppe, Justin O. and Venditti, Richard A. and Rojas, Orlando J.}, year={2012}, month={Mar}, pages={202–209} }
 @article{csoka_hoeger_rojas_peszlen_pawlak_peralta_2012, title={Piezoelectric Effect of Cellulose Nanocrystals Thin Films}, volume={1}, ISSN={2161-1653 2161-1653}, url={http://dx.doi.org/10.1021/mz300234a}, DOI={10.1021/mz300234a}, abstractNote={Ultrathin films of aligned cellulose nanocrystals (CNCs) were assembled on mica supports by using electric field-assisted shear. The relationship between polarization gradients and strain mechanics of the obtained films was examined by monitoring their deflection with an atomic force microscope operated in contact mode. The piezoelectric response of the films was ascribed to the collective contribution of the asymmetric crystalline structure of the cellulose crystals. The magnitude of the effective shear piezoelectric constant (d25) of highly ordered CNC films was determined to be 2.1 Å/V, which is comparable to that of a reference film of a piezoelectric metal oxide.}, number={7}, journal={ACS Macro Letters}, publisher={American Chemical Society (ACS)}, author={Csoka, Levente and Hoeger, Ingrid C. and Rojas, Orlando J. and Peszlen, Ilona and Pawlak, Joel J. and Peralta, Perry N.}, year={2012}, month={Jun}, pages={867–870} }
 @article{orelma_filpponen_johansson_osterberg_rojas_laine_2012, title={Surface Functionalized Nanofibrillar Cellulose (NFC) Film as a Platform for Immunoassays and Diagnostics}, volume={7}, ISSN={["1559-4106"]}, DOI={10.1007/s13758-012-0061-7}, abstractNote={We introduce a new method to modify films of nanofibrillated cellulose (NFC) to produce non-porous, water-resistant substrates for diagnostics. First, water resistant NFC films were prepared from mechanically disintegrated NFC hydrogel, and then their surfaces were carboxylated via TEMPO-mediated oxidation. Next, the topologically functionalized film was activated via EDS/NHS chemistry, and its reactivity verified with bovine serum albumin and antihuman IgG. The surface carboxylation, EDC/NHS activation and the protein attachment were confirmed using quartz crystal microbalance with dissipation, contact angle measurements, conductometric titrations, X-ray photoelectron spectroscopy and fluorescence microscopy. The surface morphology of the prepared films was investigated using confocal laser scanning microscopy and atomic force microscopy. Finally, we demonstrate that antihuman IgG can be immobilized on the activated NFC surface using commercial piezoelectric inkjet printing.}, number={1-4}, journal={BIOINTERPHASES}, author={Orelma, Hannes and Filpponen, Ilari and Johansson, Leena-Sisko and Osterberg, Monika and Rojas, Orlando J. and Laine, Janne}, year={2012}, month={Dec} }
 @article{jin_lucia_rojas_hubbe_pawlak_2012, title={Survey of Soy Protein Flour as a Novel Dry Strength Agent for Papermaking Furnishes}, volume={60}, ISSN={["1520-5118"]}, DOI={10.1021/jf303023j}, abstractNote={A series of experiments were conducted on recycled pulp samples for the novel purpose of determining the efficacy of employing soy protein flour to increase the strength of dry paper. Values of short span compression and tensile strength were the prime criteria for comparison based on industrial considerations. Various conditions were considered to uncover effective schemes for applying the soy proteins under industrial-like papermaking conditions including alkaline versus acidic as well as high or low ionic content papermaking conditions. A hybrid system of starch, a dry strength additive currently used in paper furnishes, and soy protein was considered to study the possible existence of any synergistic chemical effects. Results indicated that a 1 part (by mass) soy protein to 3 parts cationic starch hybrid system resulted in the highest strength increase in comparison to solely either the soy protein or the cationic starch as dry strength additives.}, number={39}, journal={JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY}, author={Jin, Haoyu and Lucia, Lucian A. and Rojas, Orlando J. and Hubbe, Martin A. and Pawlak, Joel J.}, year={2012}, month={Oct}, pages={9828–9833} }
 @article{liu_li_krause_rojas_pasquinelli_2012, title={The Soft-Confined Method for Creating Molecular Models of Amorphous Polymer Surfaces}, volume={116}, ISSN={["1520-6106"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863136276&partnerID=MN8TOARS}, DOI={10.1021/jp209024r}, abstractNote={The goal of this work was to use molecular dynamics (MD) simulations to build amorphous surface layers of polypropylene (PP) and cellulose and to inspect their physical and interfacial properties. A new method to produce molecular models for these surfaces was developed, which involved the use of a "soft" confining layer comprised of a xenon crystal. This method compacts the polymers into a density distribution and a degree of molecular surface roughness that corresponds well to experimental values. In addition, calculated properties such as density, cohesive energy density, coefficient of thermal expansion, and the surface energy agree with experimental values and thus validate the use of soft confining layers. The method can be applied to polymers with a linear backbone such as PP as well as those whose backbones contain rings, such as cellulose. The developed PP and cellulose surfaces were characterized by their interactions with water. It was found that a water nanodroplet spreads on the amorphous cellulose surfaces, but there was no significant change in the dimension of the droplet on the PP surface; the resulting MD water contact angles on PP and amorphous cellulose surfaces were determined to be 106 and 33°, respectively.}, number={5}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society}, author={Liu, Hongyi and Li, Yan and Krause, Wendy E. and Rojas, Orlando J. and Pasquinelli, Melissa A.}, year={2012}, month={Feb}, pages={1570–1578} }
 @article{ferrer_filpponen_rodriguez_laine_rojas_2012, title={Valorization of residual Empty Palm Fruit Bunch Fibers (EPFBF) by microfluidization: Production of nanofibrillated cellulose and EPFBF nanopaper}, volume={125}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2012.08.108}, abstractNote={Different cellulose pulps were produced from sulfur-free chemical treatments of Empty Palm Fruit Bunch Fibers (EPFBF), a by-product from palm oil processing. The pulps were microfluidized for deconstruction into nanofibrillated cellulose (NFC) and nanopaper was manufactured by using an overpressure device. The morphological and structural features of the obtained NFCs were characterized via atomic force and scanning electron microscopies. The physical properties as well as the interactions with water of sheets from three different pulps were compared with those of nanopaper obtained from the corresponding NFC. Distinctive chemical and morphological characteristics and ensuing nanopaper properties were generated by the EPFBF fibers. The NFC grades obtained compared favorably with associated materials typically produced from bleached wood fibers. Lower water absorption, higher tensile strengths (107–137 MPa) and elastic modulus (12–18 GPa) were measured, which opens the possibility for valorization of such widely available bioresource.}, journal={BIORESOURCE TECHNOLOGY}, author={Ferrer, Ana and Filpponen, Ilari and Rodriguez, Alejandro and Laine, Janne and Rojas, Orlando J.}, year={2012}, month={Dec}, pages={249–255} }
 @article{spence_venditti_rojas_habibi_pawlak_2011, title={A comparative study of energy consumption and physical properties of microfibrillated cellulose produced by different processing methods}, volume={18}, ISSN={0969-0239 1572-882X}, url={http://dx.doi.org/10.1007/s10570-011-9533-z}, DOI={10.1007/s10570-011-9533-z}, number={4}, journal={Cellulose}, publisher={Springer Science and Business Media LLC}, author={Spence, Kelley L. and Venditti, Richard A. and Rojas, Orlando J. and Habibi, Youssef and Pawlak, Joel J.}, year={2011}, month={Apr}, pages={1097–1111} }
 @article{li_liu_song_rojas_hinestroza_2011, title={Adsorption and Association of a Symmetric PEO-PPO-PEO Triblock Copolymer on Polypropylene, Polyethylene, and Cellulose Surfaces}, volume={3}, ISSN={["1944-8244"]}, DOI={10.1021/am200264r}, abstractNote={The association of a symmetric polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO(19)-PPO(29)-PEO(19)) triblock copolymer adsorbed from aqueous solutions onto polypropylene (PP), polyethylene (PE), and cellulose surfaces was probed using Atomic Force Microscopy (AFM). Significant morphological differences between the polyolefin substrates (PP and PE) and the cellulose surfaces were observed after immersion of the films in the PEO(19)-PPO(29)-PEO(19) solutions. When the samples were scanned, while immersed in solutions of the triblock copolymer, it was revealed that the structures adsorbed on the polyolefin surfaces were smoothed by the adsorbed PEO(19)-PPO(29)-PEO(19). In contrast, those structures on the hydrophilic cellulose surfaces were sharpened. These observations were related to the roughness of the substrate and the energy of interaction between the surfaces and the PEO and PPO polymer segments. The interaction energy between each of the blocks and the surface was calculated using molecular dynamics simulations. It is speculated that the associative structures amply reported in aqueous solution at concentrations above the critical micelle concentration, CMC, are not necessarily preserved upon adsorption; instead, it appears that molecular arrangements of the anchor-buoy type and hemimicelles prevail. The reported data suggests that the roughness of the surface, as well as its degree of hydrophobicity, have a large influence on the nature of the resulting adsorbed layer. The reported observations are valuable in explaining the behavior of finishing additives and lubricants commonly used in textile and fiber processing, as well as the effect of the morphology of the boundary layers on friction and wear, especially in the case of symmetric triblock copolymers, which are commonly used as antifriction, antiwear additives.}, number={7}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Li, Yan and Liu, Hongyi and Song, Junlong and Rojas, Orlando J. and Hinestroza, Juan P.}, year={2011}, month={Jul}, pages={2349–2357} }
 @article{liu_vesterinen_genzer_seppala_rojas_2011, title={Adsorption of PEO-PPO-PEO Triblock Copolymers with End-Capped Cationic Chains of Poly(2-dimethylaminoethyl methacrylate)}, volume={27}, ISSN={["0743-7463"]}, DOI={10.1021/la201596x}, abstractNote={We study the adsorption of a symmetric triblock copolymer of ethylene oxide, EO, and propylene oxide, PO, end-capped with quarternized poly(2-dimethylaminoethyl methacrylate), DMAEMA (DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24)). Light scattering and tensiometry are used to measure the relative size of the associated structures and surface excess at the air-liquid interface. The adsorbed amount, the amount of coupled water, and the viscoelasticity of the adsorbed polymer layer are measured on hydrophobic and hydrophilic surfaces (polypropylene, cellulose, and silica) by using quartz crystal microgravimetry (QCM) and surface plasmon resonance (SPR) at different ionic strengths and temperatures. The results of the experiments are compared with those obtained after adsorption of the uncharged precursor copolymer, without the cationic end-caps (EO(132)PO(50)EO(132)). DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) possesses higher affinity with the negatively charged silica and cellulose surfaces while the uncharged copolymer adsorbs to a larger extent on polypropylene surfaces. In this latter case, adsorption increases with increasing solution ionic strength and temperature. Adsorption of EO(132)PO(50)EO(132) on silica surfaces has little effect on the water contact angle (WCA), while adsorption of DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) increases the WCA of silica to 32°, indicating a large density of exposed PPO blocks upon adsorption. After adsorption of EO(132)PO(50)EO(132) and DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) on PP, the WCA is reduced by ≈14° and ≈28°, respectively, due to the exposed hydrophilic EO and highly water-soluble DMAEMA segments on the surfaces. The extent of surface coverage at saturation at the polypropylene/liquid interfaces (≈31 and 40 nm(2)/molecule obtained by QCM and SPR, respectively) is much lower, as expected, when compared with results obtained at the air/liquid interface, where a tighter packing is observed. The percentage of water coupled to the adsorbed cationic polymer decreases with solution ionic strength. Overall, these observations are ascribed to the effects of electrostatic screening, polymer hydrodynamic size, and solvency.}, number={16}, journal={LANGMUIR}, author={Liu, Xiaomeng and Vesterinen, Arja-Helena and Genzer, Jan and Seppala, Jukka V. and Rojas, Orlando J.}, year={2011}, month={Aug}, pages={9769–9780} }
 @article{cao_habibi_magalhaes_rojas_lucia_2011, title={Cellulose nanocrystals-based nanocomposites: fruits of a novel biomass research and teaching platform}, volume={100}, number={8}, journal={Current Science}, author={Cao, X. D. and Habibi, Y. and Magalhaes, W. L. E. and Rojas, O. J. and Lucia, L. A.}, year={2011}, pages={1172–1176} }
 @article{csoka_hoeger_peralta_peszlen_rojas_2011, title={Dielectrophoresis of cellulose nanocrystals and alignment in ultrathin films by electric field-assisted shear assembly}, volume={363}, ISSN={["1095-7103"]}, DOI={10.1016/j.jcis.2011.07.045}, abstractNote={Ultrathin films of cellulose nanocrystals (CNCs) are obtained by using a convective assembly setup coupled with a low-strength external AC electric field. The orientation and degree of alignment of the rod-like nanoparticles are controlled by the applied field strength and frequency used during film formation. Calculated dipole moments and Clausius-Mossotti factors allowed the determination of the critical frequencies, the peak dielectrophoresis as well as the principal orientation of the CNCs in the ultrathin films. As a result of the combination of shear forces and low electric field highly ultrathin films with controlled, unprecedented CNC alignment are achieved.}, number={1}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Csoka, Levente and Hoeger, Ingrid C. and Peralta, Perry and Peszlen, Ilona and Rojas, Orlando J.}, year={2011}, month={Nov}, pages={206–212} }
 @article{wang_hauser_laine_rojas_2011, title={Multilayers of Low Charge Density Polyelectrolytes on Thin Films of Carboxymethylated and Cationic Cellulose}, volume={25}, ISSN={["1568-5616"]}, DOI={10.1163/016942410x525876}, abstractNote={Multilayers with low charge density polyelectrolytes assembled on thin films of cellulose were studied by piezoelectric microgravimetry. The substrates were produced from colloidal suspensions of cotton fibers before and after modification with cationic and anionic groups via epoxy intermediates of quaternary ammonium and carboxymethylation, respectively. Two different levels of ionicity were used for each cellulosic substrate in order to investigate the role of the supporting surface in the buildup of the multilayer. It was found that while electrostatic interactions were leading factors in the assembly of high molecular weight, low charge density polyelectrolytes, other effects such as van der Waals and secondary cooperative forces played important roles. The charge properties of the substrate and the adsorbing polymer were relevant to the behavior of the self-assembled multilayers. Sequential additions of weak polyelectrolytes formed viscoelastic layers on all cellulose substrates. Adsorption of the first layer depended heavily on the charge characteristics of the substrate while the buildup of subsequent layers was mainly affected by the outermost adsorbed polymer. The polyelectrolyte multilayer formation with highest total adsorbed mass occurred on unmodified cellulose surfaces; therefore, in the case of the low charge density polyelectrolytes studied, substrate ionicity and functionalization may not be a requirement. Finally, the effect of anionic weak polyelectrolytes added after the first adsorbed polymer pair is highlighted in the context of reported observations for polyelectrolytes of high charge density.}, number={6-7}, journal={JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY}, author={Wang, Zhengjia and Hauser, Peter J. and Laine, Janne and Rojas, Orlando J.}, year={2011}, pages={643–660} }
 @article{liu_goli_genzer_rojas_2011, title={Multilayers of Weak Polyelectrolytes of Low and High Molecular Mass Assembled on Polypropylene and Self-Assembled Hydrophobic Surfaces}, volume={27}, ISSN={["0743-7463"]}, DOI={10.1021/la200349p}, abstractNote={Hydrophobic self-assembled octadecyltrichlorosilane (ODTS), ultrathin films of polypropylene, and ODTS modified with cationic dioctadecyldimethylammonium bromide are employed as substrates for deposition of multilayers of poly(allylamine hydrochloride) and poly(acrylic acid) from aqueous solution. The assembly of highly dissipative polyelectrolyte multilayers (PEMs) is demonstrated by quartz crystal microgravimetry. The initial rate of adsorption is faster and the adsorbed amount larger on the cationic surface, while the detailed structure of the PEMs, as determined by atomic force microscopy imaging, is related primarily to the molecular weight of the adsorbing polymers. A more extensive PEM adsorption on the hydrophobic surfaces takes place with increasing ionic strength of the background electrolyte solution. The water contact angle depends on the type of polymer adsorbed as the outermost layer, indicating that, despite the expected interdiffusion for the different polymer chains, there is a net macromolecular segregation to the free surface. Surface modification with the high molecular weight PEMs produces a more marked reduction of the hydrophilicity of the substrate.}, number={8}, journal={LANGMUIR}, author={Liu, Xiaomeng and Goli, Kiran K. and Genzer, Jan and Rojas, Orlando J.}, year={2011}, month={Apr}, pages={4541–4550} }
 @article{hubbe_wu_rojas_park_2011, title={Permeation of a cationic polyelectrolyte into mesoporous silica Part 3. Using adsorption isotherms to elucidate streaming potential results}, volume={381}, number={1-3}, journal={Colloids and Surfaces. A, Physicochemical and Engineering Aspects}, author={Hubbe, M. A. and Wu, N. and Rojas, O. J. and Park, S.}, year={2011}, pages={1–6} }
 @article{taajamaa_rojas_laine_kontturi_2011, title={Phase-specific pore growth in ultrathin bicomponent films from cellulose-based polysaccharides}, volume={7}, ISSN={["1744-6848"]}, DOI={10.1039/c1sm06020a}, abstractNote={The preparation of ultrathin (<100 nm) bicomponent films from hydrophobic polysaccharides with phase-specific pore growth was demonstrated and the underlying phenomena behind morphology formation were fundamentally investigated. The films were constructed, in a single-step process, by spin coating mixtures of trimethylsilyl cellulose (TMSC) and cellulose triacetate (CTA) from a common solvent. Atomic force microscopy (AFM) revealed a nano- and micron-scale phase separated structure, typical for interfacial polymer blends. Vertical phase separation had resulted in a continuous layer of TMSC next to the substrate with laterally phase separated CTA and TMSC on top. Furthermore, X-ray photoelectron spectroscopy (XPS) and contact angle measurements indicated the presence of a thin overlayer of TMSC. In addition, increased relative humidity conditions during spin coating resulted in the formation of pores when the CTA weight percent in the blend was in the range from 17 to 83% (i.e., in TMSC/CTA blend ratios 5 : 1, 2 : 1, 1 : 2, and 1 : 5). Closer analysis of the morphology indicated that the pores resided exclusively in the CTA phase. Hypothetically, the formation of the observed peculiar morphologies was ascribed to various phenomena occurring upon spin coating: vertical and lateral polymer phase separation, dewetting under humid atmosphere, and layer inversion during dewetting. It is concluded that the obtained ultrathin polysaccharide films with tailored surface pores, morphology and wettability are expected to be useful in emerging nanotechnologies while having the advantage of an effortless manufacturing process.}, number={21}, journal={SOFT MATTER}, author={Taajamaa, Laura and Rojas, Orlando J. and Laine, Janne and Kontturi, Eero}, year={2011}, pages={10386–10394} }
 @article{alvarez_rojano_almaza_rojas_ganan_2011, title={Self-Bonding Boards From Plantain Fiber Bundles After Enzymatic Treatment: Adhesion Improvement of Lignocellulosic Products by Enzymatic Pre-Treatment}, volume={19}, ISSN={["1572-8919"]}, DOI={10.1007/s10924-010-0260-6}, number={1}, journal={JOURNAL OF POLYMERS AND THE ENVIRONMENT}, author={Alvarez, Catalina and Rojano, Benjamin and Almaza, Ovidio and Rojas, Orlando J. and Ganan, Piedad}, year={2011}, month={Mar}, pages={182–188} }
 @article{zoppe_österberg_venditti_laine_rojas_2011, title={Surface Interaction Forces of Cellulose Nanocrystals Grafted with Thermoresponsive Polymer Brushes}, volume={12}, ISSN={1525-7797 1526-4602}, url={http://dx.doi.org/10.1021/bm200551p}, DOI={10.1021/bm200551p}, abstractNote={The colloidal stability and thermoresponsive behavior of poly(N-isopropylacrylamide) brushes grafted from cellulose nanocrystals (CNCs) of varying graft densities and molecular weights was investigated. Indication of the grafted polymer brushes was obtained after AFM imaging of CNCs adsorbed on silica. Also, aggregation of the nanoparticles carrying grafts of high degree of polymerization was observed. The responsiveness of grafted CNCs in aqueous dispersions and as an ultrathin film was evaluated by using light scattering, viscosimetry, and colloidal probe microscopy (CPM). Light transmittance measurements showed temperature-dependent aggregation originating from the different graft densities and molecular weights. The lower critical solution temperature (LCST) of grafted poly(NiPAAm) brushes was found to decrease with the ionic strength, as is the case for free poly(NiPAAm) in aqueous solution. Thermal responsive behavior of grafted CNCs in aqueous dispersions was observed by a sharp increase in dispersion viscosity as the temperature approached the LCST. CPM in liquid media for asymmetric systems consisting of ultrathin films of CNCs and a colloidal silica probe showed the distinctive effects of the grafted polymer brushes on interaction and adhesive forces. The origin of such forces was found to be mainly electrostatic and steric in the case of bare and grafted CNCs, respectively. A decrease in the onset of attractive and adhesion forces of grafted CNCs films were observed with the ionic strength of the aqueous solution. The decreased mobility of polymer brushes upon partial collapse and decreased availability of hydrogen bonding sites with higher electrolyte concentration were hypothesized as the main reasons for the less prominent polymer bridging between interacting surfaces.}, number={7}, journal={Biomacromolecules}, publisher={American Chemical Society (ACS)}, author={Zoppe, Justin O. and Österberg, Monika and Venditti, Richard A. and Laine, Janne and Rojas, Orlando J.}, year={2011}, month={Jun}, pages={2788–2796} }
 @article{spence_venditti_rojas_pawlak_hubbe_2011, title={Water vapor barrier properties of coated and filled microfibrillated cellulose composite films}, volume={6}, DOI={10.15376/biores.6.4.4370-4388}, abstractNote={Microfibrillated celluloses (MFCs) have mechanical properties sufficient for packaging applications, but lack in comparison to petroleum-based plastics in water vapor barrier properties. These properties can be modified by the use of mineral fillers, added within the film structure, or waxes, as surface coatings. In this investigation it was found that addition of fillers resulted in films with lower densities but also lower water vapor transmission rates. This was hypothesized to be due to decreased water vapor solubility in the films. Associated transport phenomena were described by the Knudsen model for diffusion but due to the limited incorporation of chemical factors in the model, accurate prediction of pore diameters for filled films was not possible. Modeling the filled-films with Fick’s equation, however, takes into account chemical differences, as observed by the calculated tortuosity values. Remarkably, coating with beeswax, paraffin, and cooked starch resulted in films with water vapor transmission rates lower than those for low density polyethylene. These coatings were modeled with a three-layer model which determined that coatings were more effective in reducing WVTR.}, number={4}, journal={BioResources}, author={Spence, K. L. and Venditti, R. A. and Rojas, O. J. and Pawlak, J. J. and Hubbe, M. A.}, year={2011}, pages={4370–4388} }
 @article{liu_wu_turgman-cohen_genzer_theyson_rojas_2010, title={Adsorption of a Nonionic Symmetric Triblock Copolymer on Surfaces with Different Hydrophobicity}, volume={26}, ISSN={["0743-7463"]}, DOI={10.1021/la100156a}, abstractNote={This study investigates the adsorption of a symmetric triblock nonionic polymer comprising ethylene oxide (EO) and propylene oxide (PO) blocks (Pluronic P-105, EO(37)PO(56)EO(37)) on a range of substrates including hydrophobic, i.e., polypropylene (PP), poly(ethylene terephthalate) (PET), nylon, and graphite, and hydrophilic, i.e., cellulose and silica. The adsorption process and the structure of the hydrated adsorbed layers are followed by quartz crystal microgravimetry (QCM), surface plasmon resonance (SPR), and atomic force microscopy. The unhydrated surfaces are characterized by ellipsometry and contact angle techniques. The adsorption kinetics and the extent of adsorption are determined by monitoring the changes in resonance frequency and refractive index of sensors coated with ultrathin films of the various substrates. Langmuirian-type adsorption kinetics is observed in all cases studied. The amount of adsorbed Pluronic on hydrophobic polymer surfaces (PP, PET, and nylon) exceeds that on the hydrophilic cellulose. The hydrophobic (graphite) mineral surface adsorbs relatively low polymer mass, typical of a monolayer, while micellar structures are observed on the hydrophilic silica surface. The amount of water coupled to the adsorbed polymer layers is quantified by combining data from QCM, and SPR are found to increase with increasing polarity of the substrate. On the basis of contact angle data, the nonhydrated adsorbed structures produce modest increases in hydrophilicity of all the substrates investigated. Overall, insights are provided into the structure and stability of both hydrated and nonhydrated adsorbed triblock copolymer.}, number={12}, journal={LANGMUIR}, author={Liu, Xiaomeng and Wu, Dong and Turgman-Cohen, Salomon and Genzer, Jan and Theyson, Thomas W. and Rojas, Orlando J.}, year={2010}, month={Jun}, pages={9565–9574} }
 @misc{habibi_lucia_rojas_2010, title={Cellulose Nanocrystals: Chemistry, Self-Assembly, and Applications}, volume={110}, ISSN={["1520-6890"]}, DOI={10.1021/cr900339w}, abstractNote={Cellulose constitutes the most abundant renewable polymer resource available today. As a chemical raw material, it is generally well-known that it has been used in the form of fibers or derivatives for nearly 150 years for a wide spectrum of products and materials in daily life. What has not been known until relatively recently is that when cellulose fibers are subjected to acid hydrolysis, the fibers yield defect-free, rod-like crystalline residues. Cellulose nanocrystals (CNs) have garnered in the materials community a tremendous level of attention that does not appear to be relenting. These biopolymeric assemblies warrant such attention not only because of their unsurpassed quintessential physical and chemical properties (as will become evident in the review) but also because of their inherent renewability and sustainability in addition to their abundance. They have been the subject of a wide array of research efforts as reinforcing agents in nanocomposites due to their low cost, availability, renewability, light weight, nanoscale dimension, and unique morphology. Indeed, CNs are the fundamental constitutive polymeric motifs of macroscopic cellulosic-based fibers whose sheer volume dwarfs any known natural or synthetic biomaterial. Biopolymers such as cellulose and lignin and † North Carolina State University. ‡ Helsinki University of Technology. Dr. Youssef Habibi is a research assistant professor at the Department of Forest Biomaterials at North Carolina State University. He received his Ph.D. in 2004 in organic chemistry from Joseph Fourier University (Grenoble, France) jointly with CERMAV (Centre de Recherche sur les Macromolecules Vegetales) and Cadi Ayyad University (Marrakesh, Morocco). During his Ph.D., he worked on the structural characterization of cell wall polysaccharides and also performed surface chemical modification, mainly TEMPO-mediated oxidation, of crystalline polysaccharides, as well as their nanocrystals. Prior to joining NCSU, he worked as assistant professor at the French Engineering School of Paper, Printing and Biomaterials (PAGORA, Grenoble Institute of Technology, France) on the development of biodegradable nanocomposites based on nanocrystalline polysaccharides. He also spent two years as postdoctoral fellow at the French Institute for Agricultural Research, INRA, where he developed new nanostructured thin films based on cellulose nanowiskers. Dr. Habibi’s research interests include the sustainable production of materials from biomass, development of high performance nanocomposites from lignocellulosic materials, biomass conversion technologies, and the application of novel analytical tools in biomass research. Chem. Rev. 2010, 110, 3479–3500 3479}, number={6}, journal={CHEMICAL REVIEWS}, author={Habibi, Youssef and Lucia, Lucian A. and Rojas, Orlando J.}, year={2010}, month={Jun}, pages={3479–3500} }
 @article{habibi_hoeger_kelley_rojas_2010, title={Development of Langmuir-Schaeffer Cellulose Nanocrystal Monolayers and Their Interfacial Behaviors}, volume={26}, ISSN={["0743-7463"]}, DOI={10.1021/la902444x}, abstractNote={Model cellulose surfaces based on cellulose nanocrystals (CNs) were prepared by the Langmuir-Schaeffer technique. Cellulose nanocrystals were obtained by acid hydrolysis of different natural fibers, producing rodlike nanoparticles with differences in charge density, aspect ratio, and crystallinity. Dioctadecyldimethylammonium bromide (DODA-Br) cationic surfactant was used to create CN-DODA complexes that allowed transfer of the CNs from the air/liquid interface in an aqueous suspension to hydrophobic solid substrates. Langmuir-Schaeffer horizontal deposition at various surface pressures was employed to carry out such particle transfer that resulted in CN monolayers coating the substrate. The morphology and chemical composition of the CN films were characterized by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Also, their swelling behavior and stability after treatment with aqueous and alkaline solutions were studied using quartz crystal microgravimetry (QCM). Overall, it is concluded that the Langmuir-Schaeffer method can be used to produce single coating layers of CNs that were shown to be smooth, stable, and strongly attached to the solid support. The packing density of the films was controlled by selecting the right combination of surface pressure during transfer to the solid substrate and the amount of CNs available relative to the cationic charges at the interface.}, number={2}, journal={LANGMUIR}, author={Habibi, Youssef and Hoeger, Ingrid and Kelley, Stephen S. and Rojas, Orlando J.}, year={2010}, month={Jan}, pages={990–1001} }
 @article{song_yamagushi_silva_hubbe_rojas_2010, title={Effect of Charge Asymmetry on Adsorption and Phase Separation of Polyampholytes on Silica and Cellulose Surfaces}, volume={114}, ISSN={["1520-6106"]}, DOI={10.1021/jp909047t}, abstractNote={The relation between the properties of polyampholytes in aqueous solution and their adsorption behaviors on silica and cellulose surfaces was investigated. Four polyampholytes carrying different charge densities but with the same nominal ratio of positive to negative segments and two structurally similar polyelectrolytes (a polyacid and a polybase) were investigated by using quartz crystal microgravimetry using silica-coated and cellulose-coated quartz resonators. Time-resolved mass and rigidity (or viscoelasticity) of the adsorbed layer was determined from the shifts in frequency (Deltaf) and energy dissipation (DeltaD) of the respective resonator. Therefore, elucidation of the dynamics and extent of adsorption, as well as the conformational changes of the adsorbed macromolecules, were possible. The charge properties of the solid surface played a crucial role in the adsorption of the studied polyampholytes, which was explained by the capability of the surface to polarize the polyampholyte at the interface. Under the same experimental conditions, the polyampholytes had a higher nominal charge density phase-separated near the interface, producing a soft, dissipative, and loosely bound layer. In the case of cellulose substrates, where adsorption was limited, electrostatic and polarization effects were concluded to be less significant.}, number={2}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Song, Junlong and Yamagushi, Takashi and Silva, Deusanilde J. and Hubbe, Martin A. and Rojas, Orlando J.}, year={2010}, month={Jan}, pages={719–727} }
 @article{peresin_habibi_vesterinen_rojas_pawlak_seppala_2010, title={Effect of Moisture on Electrospun Nanofiber Composites of Poly(vinyl alcohol) and Cellulose Nanocrystals}, volume={11}, ISSN={["1526-4602"]}, DOI={10.1021/bm1006689}, abstractNote={The effect of humidity on the morphological and thermomechanical properties of electrospun poly(vinyl alcohol) (PVA) fiber mats reinforced with cellulose nanocrystals (CNs) was investigated. Scanning electron microscopy (SEM) images revealed that the incorporation of CNs improved the morphological stability of the composite fibers even in high humidity environments. Thermal and mechanical properties of the electrospun fiber mats were studied by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and large deformation tensile tests under controlled humidity and temperatures. The balance between the moisture-induced plasticization and the reinforcing effect of rigid CN particles was critical in determining the thermomechanical behaviors of the electrospun fiber mats. Results indicated that the stabilizing effect of the CNs in the PVA matrix might be compromised by water absorption, disrupting the hydrogen bonding within the structure. The amount of this disruption depended on the surrounding humidity and the CN loading. The reduction in tensile strength of neat PVA fiber mats as they were conditioned from low relative humidity (10% RH) to high relative humidity (70% RH) was found to be about 80%, from 1.5 to 0.4 MPa. When the structure was reinforced with CNs, the reduction in strength was limited to 40%, from 2 to 0.8 MPa over the same range in relative humidity. More importantly, the CN-loaded PVA fiber mats showed a reversible recovery in mechanical strength after cycling the relative humidity. Finally, humidity treatments of the composite PVA fiber mats induced significant enhancement of their strength as a result of the adhesion between the continuous matrix and the CNs.}, number={9}, journal={BIOMACROMOLECULES}, author={Peresin, Maria S. and Habibi, Youssef and Vesterinen, Arja-Helena and Rojas, Orlando J. and Pawlak, Joel J. and Seppala, Jukka V.}, year={2010}, month={Sep}, pages={2471–2477} }
 @article{hu_heitmann_rojas_pawlak_argyropoulos_2010, title={Monitoring Cellulase Protein Adsorption and Recovery Using SDS-PAGE}, volume={49}, ISSN={0888-5885 1520-5045}, url={http://dx.doi.org/10.1021/ie100731b}, DOI={10.1021/ie100731b}, abstractNote={Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was employed to study the sorption behaviors of cellulases on microcrystalline celluloses and hardwood pulp. The adsorption and recovery of cellulases from Aspergillus niger and Trichoderma reesei were investigated at 25 °C. Cellulase recovery was conducted by rinsing adsorbed enzymes with sodium acetate buffer, Milli-Q water, and sodium hydroxide solution. The initial, equilibrium, and recovered enzymes were analyzed using SDS-PAGE gels. Gels were scanned and analyzed using ImagePro software. The molecular weights of cellulase proteins were determined using a protein marker having seven known proteins. The cellulase system from Trichoderma reesei had a higher adsorption on all substrates studied than the cellulase system from Aspergillius niger, and higher pH favored desorption from the substrates studied. Experimental results also demonstrated that adsorption and desorption amounts determined by SDS-PAGE were proportional to protein concentrations in their crude mixtures.}, number={18}, journal={Industrial & Engineering Chemistry Research}, publisher={American Chemical Society (ACS)}, author={Hu, Gang and Heitmann, John A., Jr. and Rojas, Orlando J. and Pawlak, Joel J. and Argyropoulos, Dimitris S.}, year={2010}, month={Sep}, pages={8333–8338} }
 @article{peresin_habibi_zoppe_pawlak_rojas_2010, title={Nanofiber Composites of Polyvinyl Alcohol and Cellulose Nanocrystals: Manufacture and Characterization}, volume={11}, ISSN={["1526-4602"]}, DOI={10.1021/bm901254n}, abstractNote={Cellulose nanocrystals (CN) were used to reinforce nanofibers in composite mats produced via electrospinning of poly(vinyl alcohol) (PVA) with two different concentrations of acetyl groups. Ultrathin cross-sections of the obtained nanocomposites consisted of fibers with maximum diameters of about 290 nm for all the CN loads investigated (from 0 to 15% CN loading). The electrospinning process did not affect the structure of the PVA polymer matrix, but its degree of crystallinity increased significantly together with a slight increase in the corresponding melting temperature. These effects were explained as being the result of alignment and enhanced crystallization of PVA chains within the individual nanofibers that were subjected to high shear stresses during electrospinning. The strong interaction of the PVA matrix with the dispersed CN phase, mainly via hydrogen bonding or bond network, was reduced with the presence of acetyl groups in PVA. Most importantly, the elastic modulus of the nanocomposite mats increased significantly as a consequence of the reinforcing effect of CNs via the percolation network held by hydrogen bonds. However, this organization-driven crystallization was limited as observed by the reduction in the degree of crystallinity of the CN-loaded composite fibers. Finally, efficient stress transfer and strong interactions were demonstrated to occur between the reinforcing CN and the fully hydrolyzed PVA electrospun fibers.}, number={3}, journal={BIOMACROMOLECULES}, author={Peresin, Maria S. and Habibi, Youssef and Zoppe, Justin O. and Pawlak, Joel J. and Rojas, Orlando J.}, year={2010}, month={Mar}, pages={674–681} }
 @article{wu_hubbe_rojas_park_2010, title={Permeation of a cationic polyelectrolyte into meso-porous silica Part 1. Factors affecting changes in streaming potential}, volume={364}, number={1-3}, journal={Colloids and Surfaces. A, Physicochemical and Engineering Aspects}, author={Wu, N. and Hubbe, M. A. and Rojas, O. J. and Park, S.}, year={2010}, pages={1–6} }
 @article{hubbe_wu_rojas_park_2010, title={Permeation of a cationic polyelectrolyte into mesoporous silica. Part 2. Effects of time and pore size on streaming potential}, volume={364}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2010.05.005}, DOI={10.1016/j.colsurfa.2010.05.005}, abstractNote={Streaming potential tests were carried out to determine effects of time and pore size in the adsorption and desorption from aqueous suspensions of cationic polyelectrolytes on silica gel particles. Results in Part 1 of this series showed that the adsorption of cationic polyelectrolytes exposed to mesoporous silica gels can be highly dependent on pH, the polyelectrolyte's molecular mass, and the solution's electrical conductivity. Also, the observed changes in streaming potential indicated that the adsorption tended to be relatively slow and incomplete under the conditions of analysis. The present results indicate that the rate of change of streaming potential is proportional to the logarithm of exposure time. The related changes in adsorbed amounts of polyelectrolyte were below the detection limits of typical polyelectrolyte titration procedures. Contrasting charge behaviors were observed on the exterior vs. interior surfaces of silica gel particles as a function of pore size, electrical conductivity, and polyelectrolyte molecular mass. Increasing ionic strength tended to enhance the effect of adsorption of high-mass cationic polymers on the outer surfaces, but produced only a relatively small effect on streaming potential related to their permeation into silica gel (nominal pore sizes of 6 nm or 30 nm). Adsorption of very-low-mass cationic polymer onto the outer surfaces and inside the 6 nm pore size silica gel appeared to be maximized at an intermediate salt level. Finally, electrokinetic tests were used for the first time in a protocol designed to provide evidence of polyelectrolyte desorption from the interiors of mesoporous materials.}, number={1-3}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Hubbe, Martin A. and Wu, Ning and Rojas, Orlando J. and Park, Sunkyu}, year={2010}, month={Jul}, pages={7–15} }
 @article{zoppe_habibi_rojas_venditti_johansson_efimenko_österberg_laine_2010, title={Poly(<i>N</i>-isopropylacrylamide) Brushes Grafted from Cellulose Nanocrystals via Surface-Initiated Single-Electron Transfer Living Radical Polymerization}, volume={11}, ISSN={1525-7797 1526-4602}, url={http://dx.doi.org/10.1021/bm100719d}, DOI={10.1021/bm100719d}, abstractNote={Cellulose nanocrystals (CNCs) or nanowhiskers produced from sulfuric acid hydrolysis of ramie fibers were used as substrates for surface chemical functionalization with thermoresponsive macromolecules. The CNCs were grafted with poly(N-isopropylacrylamide) brushes via surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) under various conditions at room temperature. The grafting process was confirmed via Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy and the different molecular masses of the grafts were quantified and found to depend on the initiator and monomer concentrations used. No observable damage occurred to the CNCs after grafting, as determined by X-ray diffraction. Size exclusion chromatography analyses of polymer chains cleaved from the cellulose nanocrystals indicated that a higher degree of polymerization was achieved by increasing initiator or monomer loading, most likely caused by local heterogeneities yielding higher rates of polymerization. It is expected that suspension stability, interfacial interactions, friction, and other properties of grafted CNCs can be controlled by changes in temperature and provide a unique platform for further development of stimuli-responsive nanomaterials.}, number={10}, journal={Biomacromolecules}, publisher={American Chemical Society (ACS)}, author={Zoppe, Justin O. and Habibi, Youssef and Rojas, Orlando J. and Venditti, Richard A. and Johansson, Leena-Sisko and Efimenko, Kirill and Österberg, Monika and Laine, Janne}, year={2010}, month={Sep}, pages={2683–2691} }
 @article{spence_venditti_habibi_rojas_pawlak_2010, title={The effect of chemical composition on microfibrillar cellulose films from wood pulps: Mechanical processing and physical properties}, volume={101}, ISSN={0960-8524}, url={http://dx.doi.org/10.1016/j.biortech.2010.02.104}, DOI={10.1016/j.biortech.2010.02.104}, abstractNote={Films of microfibrillated celluloses (MFCs) from pulps of different yields, containing varying amounts of extractives, lignin, and hemicelluloses, were produced by combining refining and high-pressure homogenization techniques. MFC films were produced using a casting-evaporation technique and the physical and mechanical properties (including density, roughness, fold endurance and tensile properties) were determined. Homogenization of bleached and unbleached Kraft pulps gave rise to highly individualized MFCs, but not for thermo-mechanical pulp (TMP). The resulting MFC films had a roughness equivalent to the surface upon which the films were cast. Interestingly, after homogenization, the presence of lignin significantly increased film toughness, tensile index, and elastic modulus. The hornification of fibers through a drying and rewetting cycle prior to refining and homogenization did not produce any significant effect compared to films from never-dried fibers, indicating that MFC films can potentially be made from low-cost recycled cellulosic materials.}, number={15}, journal={Bioresource Technology}, publisher={Elsevier BV}, author={Spence, Kelley L. and Venditti, Richard A. and Habibi, Youssef and Rojas, Orlando J. and Pawlak, Joel J.}, year={2010}, month={Aug}, pages={5961–5968} }
 @article{spence_venditti_rojas_habibi_pawlak_2010, title={The effect of chemical composition on microfibrillar cellulose films from wood pulps: water interactions and physical properties for packaging applications}, volume={17}, ISSN={0969-0239 1572-882X}, url={http://dx.doi.org/10.1007/s10570-010-9424-8}, DOI={10.1007/s10570-010-9424-8}, number={4}, journal={Cellulose}, publisher={Springer Science and Business Media LLC}, author={Spence, Kelley L. and Venditti, Richard A. and Rojas, Orlando J. and Habibi, Youssef and Pawlak, Joel J.}, year={2010}, month={May}, pages={835–848} }
 @article{song_liang_liu_krause_hinestroza_rojas_2009, title={Development and characterization of thin polymer films relevant to fiber processing}, volume={517}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2009.03.015}, abstractNote={Dilute solutions of cellulose, polypropylene, polyethylene, nylon and polyester were spun cast onto gold and silica wafers to generate thin films of these polymers, which are commonly used in the manufacture of synthetic fibers. The thin films were used as substrates in the quartz crystal microbalance and nano-indentation techniques to monitor adsorption and friction behaviors after treatment with a polymer solution (as a mimic of a textile finish). The spin coating conditions were optimized in terms of the resulting film morphology, thickness and surface energy. Atomic force microscopy, X-ray photoelectron spectrometry, ellipsometry and contact angle were used to probe the physical and surface properties of the resulting films. Overall, we developed thin films that are helpful to inquire, at the molecular level, phenomena relevant to fiber and textile processing including swelling, degradation, and adsorption of polymers and surfactants.}, number={15}, journal={THIN SOLID FILMS}, author={Song, Junlong and Liang, Jing and Liu, Xiaomeng and Krause, Wendy E. and Hinestroza, Juan P. and Rojas, Orlando J.}, year={2009}, month={Jun}, pages={4348–4354} }
 @article{kim_montero_habibi_hinestroza_genzer_argyropoulos_rojas_2009, title={Dispersion of Cellulose Crystallites by Nonionic Surfactants in a Hydrophobic Polymer Matrix}, volume={49}, ISSN={["1548-2634"]}, DOI={10.1002/pen.21417}, abstractNote={Abstract}, number={10}, journal={POLYMER ENGINEERING AND SCIENCE}, author={Kim, Jooyoun and Montero, Gerardo and Habibi, Youssef and Hinestroza, Juan P. and Genzer, Jan and Argyropoulos, Dimitris S. and Rojas, Orlando J.}, year={2009}, month={Oct}, pages={2054–2061} }
 @article{rojas_montero_habibi_2009, title={Electrospun Nanocomposites from Polystyrene Loaded with Cellulose Nanowhiskers}, volume={113}, ISSN={["1097-4628"]}, DOI={10.1002/app.30011}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Rojas, Orlando J. and Montero, Gerardo A. and Habibi, Youssef}, year={2009}, month={Jul}, pages={927–935} }
 @inbook{silva_rojas_park_hubbe_2009, title={Evaluation of adsorbed polyampholyte layers by using quartz crystal microbalance}, booktitle={10th International Symposium on Process Systems Engineering -- (Computer-aided chemical engineering, 7)}, publisher={Amsterdam: Elsevier}, author={Silva, D. J. and Rojas, O. J. and Park, S. W. and Hubbe, M. A.}, editor={R. M. De Brito Alves, C. A. Oller do Nascimento and Biscaia, E. C.Editors}, year={2009} }
 @article{hu_heitmann_rojas_2009, title={In Situ Monitoring of Cellulase Activity by Microgravimetry with a Quartz Crystal Microbalance}, volume={113}, ISSN={["1520-6106"]}, DOI={10.1021/jp907155v}, abstractNote={Quartz crystal microgravimetry (QCM) was used to investigate the interactions between cellulase enzymes and model cellulose substrates. The substrates consisted of thin films of cellulose that were spin-coated onto polyvinylamine (PVAm) precoated quartz crystal sensors carrying conductive gold surfaces. In QCM the quartz crystals are piezoelectrically driven and the frequency and dissipation shifts allow monitoring of substrate hydrolysis at various temperatures and enzyme concentrations in situ and in real time. The changes in frequency of cellulose-coated quartz resonators during their incubation in cellulase solutions were related to contributions from the liquid phase properties, the adsorptions of cellulase enzymes, and the hydrolysis of the substrate. Cellulase adsorption was found to be nonspecific and irreversible on gold-, PVAm-, and cellulose-coated quartz crystal sensors. The contribution to frequency shifts due to the bulk fluid properties of the cellulase solutions (at concentrations lower than 0.5 mg/mL) was minimal compared to the frequency shifts produced by cellulase binding. The maximum frequency decreases were fitted to a Langmuir model. The adsorption constant and the maximum adsorption were estimated by the fitting parameters of this model. The hydrolysis process was modeled by using a dose-response model that was then used to estimate the maximum hydrolysis rate, to compare the relative effects of temperature on adsorption and hydrolysis rate, and to obtain the apparent activation energy of cellulose hydrolysis. The hydrolysis rate increased with incubation temperature while apparent adsorption decreased. The apparent activation energy for the hydrolysis of the cellulose films employed was calculated to be 37 kJ/mol.}, number={44}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Hu, Gang and Heitmann, John A., Jr. and Rojas, Orlando J.}, year={2009}, month={Nov}, pages={14761–14768} }
 @inbook{rojas_lucia_habibi_stubenrauch_2009, title={Interfacial properties of sugar-based surfactants}, ISBN={9781893997677}, booktitle={Bio-based surfactants and detergents: Synthesis, properties, and applications}, publisher={Urbana, IL: AOCS Press}, author={Rojas, O. J. and Lucia, L. A. and Habibi, Y. and Stubenrauch, C.}, year={2009} }
 @inproceedings{yamaguchi_hubbe_rojas_2009, title={Investigation of adsorption behaviors of polyampholytes}, volume={76}, booktitle={Kami Parupu Kenkyu? Happyo?kai: Ko?en yo?shishu?}, author={Yamaguchi, T and Hubbe, M. A. and Rojas, O. J.}, year={2009}, pages={6–9} }
 @article{silva_rojas_hubbe_park_yamaguchi_song_2009, title={Polyampholytes: Their use in papermaking and their solution and adsorption behaviors}, volume={70}, number={9}, journal={O Papel}, author={Silva, D. J and Rojas, O. J. and Hubbe, M. A and Park, S. W. and Yamaguchi, T. and Song, J.}, year={2009}, pages={40–50} }
 @article{hu_heitmann_rojas_2009, title={Quantification of Cellulase Activity Using the Quartz Crystal Microbalance Technique}, volume={81}, ISSN={["1520-6882"]}, DOI={10.1021/ac802318t}, abstractNote={The development of more efficient utilization of biomass has received increased attention in recent years. Cellulases play an important role in processing biomass through advanced biotechnological approaches. Both the development and the application of cellulases require an understanding of the activities of these enzymes. A new method to determine the activity of cellulase has been developed using a quartz crystal microbalance (QCM) technique. We compare the results from this technique with those from the IUPAC (International Union of Pure and Applied Chemistry) dinitrosalicylic acid (DNS) standard method and also from biccinchoninic acid and ion chromatography methods. It is shown that the QCM technique provides results closer to those obtained by measuring the actual reducing sugars. The elimination of the use of color development in the standard redox methods makes the QCM platform easier to implement; it also allows more flexibility in terms of the nature of the substrate. Finally, validation of the proposed method was carried out by relating the crystallinity of different substrates to the cellulase activity. Numerical values of cellulase activities measured with the QCM method showed that celluloses with higher crystallinity indices were hydrolyzed slower and to a lower extent than those of lower crystallinity indices for the cellulase mixtures examined.}, number={5}, journal={ANALYTICAL CHEMISTRY}, author={Hu, Gang and Heitmann, John A., Jr. and Rojas, Orlando J.}, year={2009}, month={Mar}, pages={1872–1880} }
 @article{zoppe_peresin_habibi_venditti_rojas_2009, title={Reinforcing Poly(ε-caprolactone) Nanofibers with Cellulose Nanocrystals}, volume={1}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/am9003705}, DOI={10.1021/am9003705}, abstractNote={We studied the use of cellulose nanocrystals (CNXs) obtained after acid hydrolysis of ramie cellulose fibers to reinforce poly(epsilon-caprolactone) (PCL) nanofibers. Chemical grafting with low-molecular-weight PCL diol onto the CNXs was carried out in an attempt to improve the interfacial adhesion with the fiber matrix. Grafting was confirmed via infrared spectroscopy and thermogravimetric analyses. The polymer matrix consisted of electrospun nanofibers that were collected as nonwoven webs. The morphology as well as thermal and mechanical properties of filled and unfilled nanofibers were elucidated by scanning electron microscopy, differential scanning calorimetry, and dynamic mechanical analysis, respectively. The addition of CNXs into PCL produced minimal changes in the thermal behavior of the electrospun fibers. However, a significant improvement in the mechanical properties of the nanofibers after reinforcement with unmodified CNXs was confirmed. Fiber webs from PCL reinforced with 2.5% unmodified CNXs showed ca. 1.5-fold increase in Young's modulus and the ultimate strength compared to PCL webs. Compared to the case of grafted nanocrystals, the unmodified ones imparted better morphological homogeneity to the nanofibrillar structure. The grafted nanocrystals had a negative effect on the morphology of nonwoven webs in which individual nanofibers became annealed during the electrospinning process and, therefore, could not be compared to neat PCL nonwoven webs. A rationalization for the different effects of grafted and unmodified CNXs in reinforcing PCL nanofibers is provided.}, number={9}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Zoppe, Justin O. and Peresin, Maria S. and Habibi, Youssef and Venditti, Richard A. and Rojas, Orlando J.}, year={2009}, month={Aug}, pages={1996–2004} }
 @article{spence_venditti_rojas_2009, title={Sugar surfactants in paper recycling}, volume={24}, DOI={10.3183/npprj-2009-24-01-p107-111}, abstractNote={The objective of this research was to evaluate surfactants based on renewable materials (sugars and proteins) for use in ink removal from recycled paper via flotation deinking. By applying green chemistry approaches we aim to minimize the environmental impact of deinking agents and to open an avenue for a number of products that are being produced from natural resources. Foamability by the respective surfactants was considered and detergency experiments via piezoelectric sensing were used to reveal fundamental differences in terms of surfactant activity. Lab scale flotation deinking efficiency was measured primarily by image analysis and flotation yield determined gravimetrically. Based on deinking efficiency versus yield results, it was demonstrated that sugar-based surfactants are viable replacements to petroleum-based surfactants in flotation.}, number={1}, journal={Nordic Pulp & Paper Research Journal}, author={Spence, K. and Venditti, R. and Rojas, O. J.}, year={2009}, pages={107–111} }
 @inbook{song_li_hinestroza_rojas_2009, title={Tools to probe nanoscale surface phenomena in cellulose thin films: Applications in the area of adsorption and friction}, ISBN={9781405167864}, DOI={10.1002/9781444307474.ch4}, abstractNote={Surfaces and interfaces play important roles in defining material interactions. Several developments in science and technology highlight the importance of interfaces in applications involving material functionalization, coatings, colloids stability, etc. (Karim and Kumar 2000). In many cases, the interfacial properties are more relevant than the nature and composition of the bulk phases and ultimately define the molecular behavior of the system. The ‘thickness’ of a boundary between two phases, if possible to define, is expected to be extremely narrow. The interface between (bio)polymers or that for a polymer-coated substrate and the surrounding medium typically entails a ‘soft’ layer with molecular or nanoscale dimensions. The use of adsorbed polymers and surfactants to modify solid surfaces offers unique possibilities to alter or regulate their properties, including surface energy, molecular assembly and composition, among others. In order to effectively or permanently modify the interfacial properties the adsorbing material (or adsorbate) has to bind to some degree or extent to the respective surface. Therefore, adsorption is fundamental in many important applications, particularly in the general fields of adhesion, colloidal stabilization, friction, and heterogeneous reactions.}, booktitle={The nanoscience and technology of renewable biomaterials}, publisher={Chichester, West Sussex, U.K.: Wiley-Blackwell}, author={Song, S. and Li, Y. and Hinestroza, J. P. and Rojas, O. J.}, editor={Lucia, L. A. and Rojas, O. J.Editors}, year={2009} }
 @article{hubbe_rojas_lucia_sain_2008, title={Cellulosic nanocomposites: A review}, volume={3}, number={3}, journal={BioResources}, author={Hubbe, M. A. and Rojas, O. J. and Lucia, L. A. and Sain, M.}, year={2008}, pages={929–980} }
 @article{hubbe_rojas_2008, title={Colloidal stability and aggregation of lignocellulosic materials in aqueous suspension: A review}, volume={3}, number={4}, journal={BioResources}, author={Hubbe, M. A. and Rojas, O. J.}, year={2008}, pages={1419–1491} }
 @article{ahola_turon_osterberg_laine_rojas_2008, title={Enzymatic Hydrolysis of Native Cellulose Nanofibrils and Other Cellulose Model Films: Effect of Surface Structure}, volume={24}, ISSN={["0743-7463"]}, DOI={10.1021/la801550j}, abstractNote={Model films of native cellulose nanofibrils, which contain both crystalline cellulose I and amorphous domains, were used to investigate the dynamics and activities of cellulase enzymes. The enzyme binding and degradation of nanofibril films were compared with those for other films of cellulose, namely, Langmuir-Schaefer and spin-coated regenerated cellulose, as well as cellulose nanocrystal cast films. Quartz crystal microbalance with dissipation (QCM-D) was used to monitor the changes in frequency and energy dissipation during incubation at varying enzyme concentrations and experimental temperatures. Structural and morphological changes of the cellulose films upon incubation with enzymes were evaluated by using atomic force microscopy. The QCM-D results revealed that the rate of enzymatic degradation of the nanofibril films was much faster compared to the other types of cellulosic films. Higher enzyme loads did not dramatically increase the already fast degradation rate. Real-time measurements of the coupled contributions of enzyme binding and hydrolytic reactions were fitted to an empirical model that closely described the cellulase activities. The hydrolytic potential of the cellulase mixture was found to be considerably affected by the nature of the substrates, especially their crystallinity and morphology. The implications of these observations are discussed in this report.}, number={20}, journal={LANGMUIR}, author={Ahola, S. and Turon, X. and Osterberg, M. and Laine, J. and Rojas, O. J.}, year={2008}, month={Oct}, pages={11592–11599} }
 @article{turon_rojas_deinhammer_2008, title={Enzymatic kinetics of cellulose hydrolysis: A QCM-D study}, volume={24}, ISSN={["0743-7463"]}, DOI={10.1021/la7032753}, abstractNote={The interactions between films of cellulose and cellulase enzymes were monitored using a quartz crystal microbalance (QCM). Real-time measurements of the coupled contributions of enzyme binding and hydrolytic reactions were fitted to a kinetic model that described closely significant cellulase activities. The proposed model combines simple Boltzmann sigmoidal and 1 - exp expressions. The obtained kinetics parameters were proven to be useful to discriminate the effects of incubation variables and also to perform enzyme screening. Furthermore, it is proposed that the energy dissipation of a film subject to enzymatic hydrolysis brings to light its structural changes. Overall, it is demonstrated that the variations registered in QCM frequency and dissipation of the film are indicative of mass and morphological transformations due to enzyme activities; these include binding phenomena, progressive degradation of the cellulose film, existence of residual, recalcitrant cellulose fragments, and the occurrence of other less apparent changes throughout the course of incubation.}, number={8}, journal={LANGMUIR}, author={Turon, Xavier and Rojas, Orlando J. and Deinhammer, Randall S.}, year={2008}, month={Apr}, pages={3880–3887} }
 @article{hu_heitmann_rojas_2008, title={Feedstock pretreatment strategies for producing ethanol from wood, bark, and forest residues}, volume={3}, number={1}, journal={BioResources}, author={Hu, G. and Heitmann, J. A. and Rojas, O. J.}, year={2008}, pages={270–294} }
 @inproceedings{wu_hubbe_rojas_yamaguchi_2008, title={Penetration of high-charge cationic polymers into silica gel particles and cellulosic fibers}, volume={Book B}, booktitle={Proceedings of the 2nd IPEC Conference}, publisher={Tianjin, China: Tianjin University of Science & Technology}, author={Wu, N. and Hubbe, M. A. and Rojas, O. J. and Yamaguchi, T.}, year={2008}, pages={626–649} }
 @article{hubbe_rojas_argyropoulos_wang_song_sulic_sezaki_2007, title={Charge and the dry-strength performance of polyampholytes. Part 2. Colloidal effects}, volume={301}, DOI={10.1016/j.colsurfa.2006.11.053}, abstractNote={Polyampholytes, which are macromolecules that contain both positive and negative ionizable groups, can provide superior strength improvements for paper manufacture, compared to the addition of simple polyelectrolytes. Colloidal effects, which were measured in solution and in fiber suspensions, were consistent with observed bonding effects. The same colloidal effects were found to correlate with the effects of pH and of the density of the ionizable groups on the polyampholytes. Tests were carried out with a series of polyampholytes having a constant ratio of cationic to anionic monomeric groups and molecular mass. Their charge density varied in the ratio 1:2:4:8. The greatest strength gains were obtained at intermediate charge density and under conditions of pH favoring instability of the aqueous polymer mixtures. Colloidal phenomena were elucidated by turbidimetric tests, sediment volumes of treated fiber suspensions, flocculation tendencies of treated fiber suspensions, and zeta potentials of probe particles.}, journal={Colloids and Surfaces. A, Physicochemical and Engineering Aspects}, author={Hubbe, M. A. and Rojas, O. J. and Argyropoulos, Dimitris and Wang, Y. and Song, J. and Sulic, N. and Sezaki, T.}, year={2007}, pages={23–32} }
 @article{wang_hubbe_rojas_argyropoulos_wang_sezaki_2007, title={Charge and the dry-strength performance of polyampholytes. Part 3: Streaming potential analysis}, volume={301}, ISSN={["1873-4359"]}, DOI={10.1016/j.colsurfa.2006.11.052}, abstractNote={Results reported in Part 1 of this series showed that paper strength improvements could be optimized by varying pH and the overall content of ionic groups in random terpolymers containing a fixed molar ratio of acidic and basic monomeric groups. Further treatment of kraft fiber slurries with polyaluminum chloride (PAC), after polyampholyte addition, yielded significant strength benefits. The present paper shows how these results can be explained in terms of the streaming potential (SP) of glass fibers, which were used as a model substrate. The data suggest that aluminum ions interact both with the anionic carboxyl groups of the polyampholytes and with anionic silanol groups at fiber surfaces. The streaming potential of the treated surfaces could be changed by varying the pH, the overall density of charged groups of the polyampholytes, the ratio of cationic to anionic groups on the polymer and by post-treatment with polyaluminum chloride.}, number={1-3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Wang, Yun and Hubbe, Martin A. and Rojas, Orlando J. and Argyropoulos, Dimitris S. and Wang, Xingwu and Sezaki, Takao}, year={2007}, month={Jul}, pages={33–40} }
 @article{hubbe_rojas_lucia_jung_2007, title={Consequences of the nanoporosity of cellulosic fibers on their streaming potential and their interactions with cationic polyelectrolytes}, volume={14}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-006-9098-4}, abstractNote={Electrokinetic tests, based on the streaming potential method, were used to elucidate interactions between cationic polyelectrolytes and cellulosic fibers and to reveal aspects of fibers' nanoporosity. The fibrillated and nanoporous nature of bleached kraft fibers gave rise to time-dependent changes in streaming potential, following treatment of the wetted fibers with poly-diallyldimethylammonium chloride. Electrokinetic test results were consistent with an expected longer time required for higher-mass polyelectrolytes to diffuse into pore spaces, compared to lower-mass polyelectrolytes. Further evidence of the relative inability of polyelectrolyte molecules to diffuse into the pores of cellulose was obtained by switching back and forth between high and low ionic strength conditions during repeated measurement of streaming potential, after the fibers had been treated with a moderate amount of cationic polymer. By changing the concentration of sodium sulfate it was possible to switch the sign of streaming potential repeatedly from positive to negative and back again. Such results imply that a continuous path for liquid flow exists either in a fibrillar layer or within the cell walls. The same concepts also helped to explain the dosages of high-charge cationic polymer needed to achieve maximum dewatering rates, as well as the results of retention experiments using positively and negatively charged microcrystalline cellulose particles.}, number={6}, journal={CELLULOSE}, author={Hubbe, Martin A. and Rojas, Orlando J. and Lucia, Lucian A. and Jung, Tae Min}, year={2007}, month={Dec}, pages={655–671} }
 @article{hubbe_rojas_lee_park_wang_2007, title={Distinctive electrokinetic behavior of nanoporous silica particles treated with cationic polyelectrolyte}, volume={292}, ISSN={["0927-7757"]}, DOI={10.1016/j.colsurfa.2006.06.034}, abstractNote={In this study we show, for the first time, that the streaming potential of aqueous suspensions of nanoporous silica gel, after treatment with the cationic polyelectrolyte poly-diallyldimethylammonium chloride (poly-DADMAC), can depend very strongly on the concentration of background electrolyte. An increase in the electrical conductivity from 60 to 1000 μS/cm resulted in an approximately 1000-fold increase in the amount of poly-DADMAC that was required to reach an endpoint of zero streaming potential. Results were explained by two contributions to the overall electrokinetic behavior—one due to the outer surfaces and another due to the interior surfaces of nanopore spaces that were inaccessible to the polyelectrolytes. Experiments with cyclical changes in salt content revealed a high degree of reversibility; such observations help to rule out explanations based on salt-induced desorption or enhancement of pore penetration. Supplementary tests with non-porous glass fibers showed no evidence of the distinctive electrokinetic behavior observed in the case of nanoporous particles. Effects of polymer molecular mass and pH, evaluated under similar experimental conditions, agreed with well-established trends.}, number={2-3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Hubbe, Martin A. and Rojas, Orlando J. and Lee, Sa Yong and Park, Sunkyu and Wang, Yun}, year={2007}, month={Jan}, pages={271–278} }
 @article{lucia_rojas_2007, title={Fiber nanotechnology: a new platform for "green" research and technological innovations}, volume={14}, ISSN={["0969-0239"]}, DOI={10.1007/s10570-007-9177-1}, number={6}, journal={CELLULOSE}, author={Lucia, Lucian A. and Rojas, Orlando J.}, year={2007}, month={Dec}, pages={539–542} }
 @inbook{rojas_bullon_ysambertt_a._d. s._salager_2007, title={Lignin as emulsion stabilizers: Materials, chemicals and energy from forest biomass}, volume={954}, ISBN={9780841239814}, booktitle={Materials, chemicals and energy from forest biomass}, publisher={Washington, DC: ACS Books}, author={Rojas, O. J. and Bullon, J. and Ysambertt, F. Forgiarini and A., Argyropoulos and D. S. and Salager, J.-L.}, year={2007}, pages={182–199} }
 @inbook{rojas_jheong_turon_argyropoulos_2007, title={Measurement of cellulase activity with piezoelectric resonators}, volume={954}, ISBN={9780841239814}, booktitle={Materials, chemicals and energy from forest biomass}, publisher={Washington, DC: ACS Books}, author={Rojas, O. J. and Jheong, C. and Turon, X. and Argyropoulos, D. S.}, year={2007}, pages={478–494} }
 @article{lucia_rojas_eds._2007, title={Nanotechnology: a fiber perspective}, volume={14}, number={6}, journal={Cellulose}, author={Lucia, L. and Rojas, O. J. and eds.}, year={2007} }
 @inbook{argyropoulos_saquing_gaspar_soriano_lucia_rojas_2007, title={Oxidative chemistry of lignin In supercritical carbon dioxide & expanded liquids}, volume={954}, ISBN={9780841239814}, DOI={10.1021/bk-2007-0954.ch020}, abstractNote={This paper explores the use of supercritical carbon dioxide (scCO{2}) as a medium for the oxidative degradation of three lignin model compounds, namely; 3-methoxy-4-hydroxy-benzaldehyde (1), 3,4-dimethoxy-benzylalcohol (2) and 3,3'-dimethoxy-5,5'-dimethyl-[1,1'-biphenyl]-2,2'-diol (3), as well as Residual Kraft Lignin (RKL), with hydrogen peroxide as the oxidant at variable temperatures and pressures. To do this we quantitatively followed the starting material and the main reaction products during the oxidative degradation. The actual yields of the various reaction products ranged from very good to almost quantitative. The most significant aspect of our findings was that peroxide-induced oxidations in scCO{2} did not require the creation of the precursor phenoxy anion since no alkali was used during our experiments. In addition, no radical coupling products were detected, signifying a novel, relatively clean and predictable product distribution in scCO{2}. Our work so far demonstrates that: - ScCO{2} oxidation conditions proceed in a manner that is rather different than for conventional aqueous systems. - Aromatic compounds, such as recalcitrant 5'5 biphenols, which are relatively stable under aqueous oxidative conditions, can be readily oxidized under scCO{2} peroxide in total absence of alkali. - The product distributions under scCO{2} oxidation conditions seem to be simpler than those that are formed under aqueous conditions in the presence of alkali. - Otherwise difficult to oxidize, residual kraft lignin is seen to be readily oxidized with peroxide in scCO{2}, selectively inducing the formation of large amounts of carboxylic acids on it via the elimination of phenolic moieties.}, booktitle={Materials, chemicals and energy from forest biomass}, publisher={Washington, DC: ACS Books}, author={Argyropoulos, Dimitris and Saquing, C. D. and Gaspar, A. R. and Soriano, N. U. and Lucia, L. A. and Rojas, O. J.}, year={2007}, pages={311–331} }
 @article{hubbe_rojas_sulic_sezaki_2007, title={Unique behavior of polyampholytes as dry-strength agents}, volume={60}, number={2}, journal={Appita Journal}, author={Hubbe, M. A. and Rojas, O. J. and Sulic, N. and Sezaki, T.}, year={2007}, pages={106–111} }
 @article{bullon_rennola_salazar_hoeger_cardenas_rojas_2007, title={Water treatment in papermaking white water loops using membrane separation techniques}, volume={30}, journal={Revista Tecnica de la Facultad de Ingenieria Universidad Del Zulia}, author={Bullon, J. and Rennola, L. and Salazar, F. and Hoeger, M. and Cardenas, A. and Rojas, O. J.}, year={2007}, pages={90–97} }
 @article{hubbe_venditti_rojas_2007, title={What happens to cellulosic fibers during papermaking and recycling? A review}, volume={2}, number={4}, journal={BioResources}, author={Hubbe, M. A. and Venditti, R. A. and Rojas, O. J.}, year={2007}, pages={739–788} }
 @article{wang_hubbe_sezaki_wang_rojas_argyropoulos_2006, title={Aspects of retention and formation - The role of polyampholyte charge density on its interactions with cellulose}, volume={21}, number={5}, journal={Nordic Pulp & Paper Research Journal}, author={Wang, Y. and Hubbe, M. A. and Sezaki, T. and Wang, X. W. and Rojas, O. J. and Argyropoulos, D. S.}, year={2006}, pages={638–645} }
 @article{song_wang_hubbe_rojas_sulic_sezaki_2006, title={Charge and the dry-strength performance of polyampholytes. Part 1, Handsheet properties and polymer solution viscosity}, volume={32}, number={3}, journal={Journal of Pulp and Paper Science}, author={Song, J. and Wang, Y. and Hubbe, M. A. and Rojas, O. J. and Sulic, N. and Sezaki, T.}, year={2006}, pages={156–162} }
 @article{hubbe_rojas_venditti_2006, title={Control of tacky deposits on paper machines - A review}, volume={21}, number={2}, journal={Nordic Pulp & Paper Research Journal}, author={Hubbe, M. A. and Rojas, O. J. and Venditti, R. A.}, year={2006}, pages={154–171} }
 @article{rojas_song_argyropoulos_2006, title={Lignin separation from kraft black liquors by tangential ultrafiltration}, volume={88}, number={1}, journal={Chimica E L'industria}, author={Rojas, O. J. and Song, J. and Argyropoulos, D. S.}, year={2006}, pages={88–95} }
 @article{argyropoulos_li_gaspar_smith_lucia_rojas_2006, title={Quantitative P-31 NMR detection of oxygen-centered and carbon-centered radical species}, volume={14}, ISSN={["1464-3391"]}, DOI={10.1016/j.bmc.2006.02.009}, abstractNote={Quantitative 31P NMR spin trapping techniques can be used as effective tools for the detection and quantification of many free radical species. Free radicals react with a nitroxide phosphorus compound, 5-diisopropoxy-phosphoryl-5-methyl-1-pyrroline-N-oxide (DIPPMPO), to form stable radical adducts, which are suitably detected and accurately quantified using (31)P NMR in the presence of phosphorus containing internal standards. Initially, the 31P NMR signals for the radical adducts of oxygen-centered (*OH, O2*-) and carbon-centered (*CH3, *CH2OH, CH2*CH2OH) radicals were assigned. Subsequently, the quantitative reliability of the developed technique was demonstrated under a variety of experimental conditions. The 31P NMR chemical shifts for the hydroxyl and superoxide reaction adducts with DIPPMPO were found to be 25.3, 16.9, and 17.1 ppm (in phosphate buffer), respectively. The 31P NMR chemical shifts for *CH3, *CH2OH, *CH(OH)CH3, and *C(O)CH3 spin adducts were 23.1, 22.6, 27.3, and 30.2 ppm, respectively. Overall, this effort forms the foundations for a targeted understanding of the nature, identity, and mechanisms of radical activity in a variety of biomolecular processes.}, number={12}, journal={BIOORGANIC & MEDICINAL CHEMISTRY}, author={Argyropoulos, Dimitris S. and Li, Hongyang and Gaspar, Armindo R. and Smith, Kamilah and Lucia, Lucian A. and Rojas, Orlando J.}, year={2006}, month={Jun}, pages={4017–4028} }
 @article{jhon_bhat_jeong_rojas_szleifer_genzer_2006, title={Salt-induced depression of lower critical solution temperature in a surface-grafted neutral thermoresponsive polymer}, volume={27}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200600031}, abstractNote={Abstract}, number={9}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Jhon, Young K. and Bhat, Rajendra R. and Jeong, Changwoo and Rojas, Orlando J. and Szleifer, Igal and Genzer, Jan}, year={2006}, month={May}, pages={697–701} }
 @misc{claesson_kjellin_rojas_stubenrauch_2006, title={Short-range interactions between non-ionic surfactant layers}, volume={8}, number={47}, journal={Physical Chemistry Chemical Physics}, author={Claesson, P. M. and Kjellin, M. and Rojas, O. J. and Stubenrauch, C.}, year={2006}, pages={5501–5514} }
 @article{argyropoulos_gaspar_lucia._j._2006, title={Supercritical CO2 oxidation of lignin: Production of high valued added products}, volume={88}, number={1}, journal={Chimica E L'industria}, author={Argyropoulos, D. S. and Gaspar, A. and Lucia., L. and J., Rojas. O.}, year={2006}, pages={74–79} }
 @article{wang_hubbe_sezaki_wang_rojas_argyropoulos_2006, title={The role of polyampholyte charge density on its interactions with cellulose}, volume={21}, number={5}, journal={Nordic Pulp & Paper Research Journal}, author={Wang, Y. and Hubbe, M. A. and Sezaki, T. and Wang, X. and Rojas, O. J. and Argyropoulos, D. S.}, year={2006}, pages={158–165} }
 @article{vangeyte_leyh_rojas_claesson_heinrich_auvray_willet_jerome_2005, title={Adsorption of poly(ethylene oxide)-b-poly(E-caprolactone) copolymers at the silica-water interface}, volume={21}, ISSN={["0743-7463"]}, DOI={10.1021/la047425+}, abstractNote={The adsorption of amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) and poly(ethylene oxide)-b-poly(gamma-methyl-epsilon-caprolactone) copolymers in aqueous solution on silica and glass surfaces has been investigated by flow microcalorimetry, small-angle neutron scattering (SANS), surface forces, and complementary techniques. The studied copolymers consist of a poly(ethylene oxide) (PEO) block of M(n) = 5000 and a hydrophobic polyester block of poly(epsilon-caprolactone) (PCL) or poly(gamma-methyl-epsilon-caprolactone) (PMCL) of M(n) in the 950-2200 range. Compared to homoPEO, the adsorption of the copolymers is significantly increased by the connection of PEO to an aliphatic polyester block. According to calorimetric experiments, the copolymers interact with the surface mainly through the hydrophilic block. At low surface coverage, the PEO block interacts with the surface such that both PEO and PCL chains are exposed to the aqueous solution. At high surface coverage, a dense copolymer layer is observed with the PEO blocks oriented toward the solution. The structure of the copolymer layer has been analyzed by neutron scattering using the contrast matching technique and by tapping mode atomic force microscopy. The experimental observations agree with the coadsorption of micelles and free copolymer chains at the interface.}, number={7}, journal={LANGMUIR}, author={Vangeyte, P and Leyh, B and Rojas, OJ and Claesson, PM and Heinrich, M and Auvray, L and Willet, N and Jerome, R}, year={2005}, month={Mar}, pages={2930–2940} }
 @article{rojas_stubenrauch_schulze-schlarmann_claesson_2005, title={Interactions between nonpolar surfaces coated with the nonionic surfactant n-dodecyl-beta-D-maltoside}, volume={21}, ISSN={["0743-7463"]}, DOI={10.1021/la051938e}, abstractNote={The forces acting between nonpolar surfaces coated with the nonionic surfactant n-dodecyl-beta-D-maltoside (beta-C(12)G(2)) were investigated at concentrations below and above the critical micelle concentration. The long-range and adhesive forces were measured with a bimorph surface force apparatus (MASIF). It was found that the effect of hydrodynamic interactions had to be taken into account for an accurate determination of the short-range static interactions. The results were compared with disjoining pressure versus thickness curves that were obtained earlier with a thin film pressure balance (TFPB). This comparison led to the conclusion that the charges observed at the air-water interface are not due to charged species present in the surfactant sample. In addition, it was observed that the stability of thin liquid films crucially depends on the surfactant's bulk concentration (c) and thus on the packing density in the adsorbed layer. The force barrier preventing removal of the surfactant layer from between two solid-liquid interfaces increases with increasing c, while for foam films it is the stability of the Newton black film that increases with c. Finally, the results obtained for beta-C(12)G(2) were compared with those obtained for the homologue n-decyl-beta-d-maltoside (beta-C(10)G(2)) as well as with those obtained for nonionic surfactants with polyoxyethylene moieties as polar groups.}, number={25}, journal={LANGMUIR}, author={Rojas, OJ and Stubenrauch, C and Schulze-Schlarmann, J and Claesson, PM}, year={2005}, month={Dec}, pages={11836–11843} }
 @inproceedings{rojas_dedinaite_byrd_hubbe_claesson_2005, title={On the origins of adhesion in papermaking systems}, booktitle={Advances in Paper Science and Technology: Transactions of the 13th Fundamental research symposium, vols 1-3}, author={Rojas, O. J. and Dedinaite, A. and Byrd, M. V. and Hubbe, M. A. and Claesson, P. M.}, year={2005}, pages={1351–1378} }
 @article{hubbe_rojas_2005, title={The paradox of papermaking}, volume={39}, number={2}, journal={Chemical Engineering Education}, author={Hubbe, M. A. and Rojas, O. J.}, year={2005}, pages={146–155} }
 @article{rojas_neuman_claesson_2005, title={Viscoelastic properties of isomeric alkylglucoside surfactants studied by surface light scattering}, volume={109}, ISSN={["1520-6106"]}, DOI={10.1021/jp054132w}, abstractNote={Surface light scattering (SLS) by capillary waves was used to investigate the adsorption behavior of non-ionic sugar surfactants at the air/liquid interface. SLS by the subphase (water) followed predictions from hydrodynamic theory. The viscoelastic properties (surface elasticity and surface viscosity) of monolayers formed by octyl beta-glucoside, octyl alpha-glucoside, and 2-ethylhexyl alpha-glucoside surfactants were quantified at submicellar concentrations. It is further concluded that a diffusional relaxation model describes the observed trends in high-frequency, nonintrusive laser light scattering experiments. The interfacial diffusion coefficients that resulted from fitting this diffusional relaxation model to surface elasticity values obtained with SLS reflect the molecular dynamics of the subphase near the interface. However, differences from the theoretical predictions indicate the existence of effects not accounted for such as thermal convection, molecular rearrangements, and other relaxation mechanisms within the monolayer. Our results demonstrate important differences in molecular packing at the air-water interface for the studied isomeric surfactants.}, number={47}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Rojas, OJ and Neuman, RD and Claesson, PM}, year={2005}, month={Dec}, pages={22440–22448} }
 @article{stubenrauch_schlarmann_rojas_claesson_2004, title={Comparison between interaction forces at air/liquid interfaces in the presence of non-ionic surfactants}, volume={41}, ISSN={["0932-3414"]}, DOI={10.3139/113.100221}, abstractNote={Abstract}, number={4}, journal={TENSIDE SURFACTANTS DETERGENTS}, author={Stubenrauch, C and Schlarmann, J and Rojas, OJ and Claesson, PM}, year={2004}, pages={174–179} }
 @article{chen_hubbe_heitmann_argyropoulos_rojas_2004, title={Dependency of polyelectrolyte complex stoichiometry on the order of addition - 2. Aluminum chloride and poly-vinylsulfate}, volume={246}, ISSN={["1873-4359"]}, DOI={10.1016/j.colsurfa.2004.07.021}, abstractNote={In the first part of this series it was shown that the stoichiometry of complexation between oppositely charged polyelectrolytes became increasingly dependent on the order of addition as the concentrations of monovalent and divalent ions were increased. This study considers the effect of aluminum ions on titrations between solutions of a strong poly-acid and a strong poly-base. In addition, the titratable charge of aluminum ion itself was also investigated. It was found that aluminum ions can interfere with the results of charge titrations, in the sense that the titration results became unpredictable. Stoichiometric relationships between the amount of aluminum present and the amount of titrant required to achieve streaming current values of zero were obtained only at pH values associated with a maximum in the amount of titrant needed to neutralize a given concentration of dissolved aluminum. The results are consistent with complexation between the anionic titrant and polynuclear species of aluminum, where the relative proportion of such species depends strongly on the molar ratio of OH to Al.}, number={1-3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Chen, JH and Hubbe, MA and Heitmann, JA and Argyropoulos, DS and Rojas, OJ}, year={2004}, month={Oct}, pages={71–79} }
 @article{stubenrauch_rojas_schlarmann_claesson_2004, title={Interactions between nonpolar surfaces coated with the nonionic surfactant hexaoxyethylene dodecyl Ether C12E6 and the origin of surface charges at the air/water interface}, volume={20}, DOI={10.1021/la.0304060}, number={12}, journal={Langmuir}, author={Stubenrauch, C. and Rojas, O. J. and Schlarmann, J. and Claesson, P. M.}, year={2004}, pages={4977–4988} }
 @misc{rojas_hubbe_2004, title={The dispersion science of papermaking}, volume={25}, ISSN={["1532-2351"]}, DOI={10.1081/DIS-200035485}, abstractNote={Abstract Paper is one of the most important inventions in the history of civilization, and it is an essential commodity to all people in the world. The fact that we make ubiquitous use of a score of paper products makes it easy to underestimate its value and significance. This review is intended to put into perspective the dispersion science involved in papermaking and to describe how our understanding of key processes has evolve since its conception, approximately 2000 years ago, from art to science. Paper is formed from a slurry of fibers and much smaller particles that are often called “fines” and other chemical additives. Ahead of the paper forming process the slurry is subjected to a series of steps, including treatment with polyionic species and passage through unit operations that impose shear forces on the papermaking suspension. These steps alternately disperse the solids apart or re‐gather them back together. The overall process is optimized to achieve a highly uniform product, while at the same time achieving high efficiency in retaining fines in the sheet and allowing water to drain relatively quickly from the wet paper as it is being formed. As we approach the 1900‐year anniversary of the first detailed account of the papermaking process, it is the goal of this review to explore the scientific principles that underlie the art of papermaking, emphasizing the state of dispersion of the fibrous slurries during various stages of the manufacturing process. Some concepts that arise out of the experience of papermakers have potential applications in other fields.}, number={6}, journal={JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY}, author={Rojas, OJ and Hubbe, MA}, year={2004}, month={Nov}, pages={713–732} }
 @inproceedings{hubbe_payne_jackson_aizpurua_rojas, title={Application of cellulosic fiber materials for the remediation of petroleum spills in water}, booktitle={Proceeding of the 4th International Conference on Pulping, Papermaking and Biotechnology (ICPPB '12), vols. I and II}, author={Hubbe, M. A. and Payne, K. C. and Jackson, C. D. and Aizpurua, C. E. and Rojas, O. J.}, pages={854–859} }
 @misc{song_rojas, title={Approaching super-hydrophobicity from cellulosic materials: A Review}, volume={28}, number={2}, journal={Nordic Pulp & Paper Research Journal}, author={Song, J. L. and Rojas, O. J.}, pages={216–238} }
 @inproceedings{ago_silveira_taajamaa_jakes_kontturi_bittencourt_laine_rojas, title={Electrospun micro-and nano- fibers from multicomponent lignocellulose systems: Functional materials with special surface, mechanical and thermal properties}, booktitle={Proceeding of the 4th International Conference on Pulping, Papermaking and Biotechnology (ICPPB '12), vols. I and II}, author={Ago, M. and Silveira, J. and Taajamaa, L. and Jakes, J. E. and Kontturi, E. and Bittencourt, E. and Laine, J. and Rojas, O. J.}, pages={873–879} }
 @article{nypelo_rojas, title={Functionalizing cellulose fibers by mineral and ceramic nanoparticle deposition}, volume={91}, number={6}, journal={American Ceramic Society Bulletin}, author={Nypelo, T. and Rojas, O. J.}, pages={28–31} }
 @article{ago_jakes_johansson_park_rojas, title={Interfacial properties of lignin-based electrospun nanofibers and films reinforced with cellulose nanocrystals}, volume={4}, number={12}, journal={ACS Applied Materials & Interfaces}, author={Ago, M. and Jakes, J. E. and Johansson, L. S. and Park, S. and Rojas, O. J.}, pages={6848–6855} }
 @inproceedings{quddus_rojas_pasquinelli, title={Molecular dynamics simulations of the thermal stability of crystalline cellulose surfaces coated with oleic acid}, volume={1107}, booktitle={Functional materials from renewable sources}, author={Quddus, M. A. A. R. and Rojas, O. J. and Pasquinelli, M. A.}, pages={191–208} }