@article{contreras_gaspar_guerra_lucia_argyropoulos_2008, title={Propensity of Lignin to Associate: Light Scattering Photometry Study with Native Lignins}, volume={9}, ISSN={["1526-4602"]}, DOI={10.1021/bm800673a}, abstractNote={Many studies of lignins in solution invoke association and aggregation phenomena to explain their solution behavior (e.g., reprecipitation onto pulp fibers, condensation, etc.). Following their colloidal (apparent) molecular weights in solution as a function of time allows us to explore observable dissociation phenomena. These measurements were carried out using multiple angle laser light scattering (MALLS) photometry in the static mode. The challenges and opportunities of measuring the specific refractive index increment (dn/dC) of lignin solutions and determining the kinetics of the dissociation process were thus investigated. Hardwood and softwood representative lignins were isolated, and method for their full dissolution in THF was further developed, which then lead to accurate dn/dC values being obtained as a function of time. When coupled to additional work using light scattering static measurements and Zimm plots for the same solutions, this effort offers insight into the aggregation and ensuing dissociative events that operate within the lignin macromolecules.}, number={12}, journal={BIOMACROMOLECULES}, author={Contreras, Sofia and Gaspar, Armindo R. and Guerra, Anderson and Lucia, Lucian A. and Argyropoulos, Dimitris S.}, year={2008}, month={Dec}, pages={3362–3369} }
 @misc{gaspar_gamelas_evtuguin_neto_2007, title={Alternatives for lignocellulosic pulp delignification using polyoxometalates and oxygen: a review}, volume={9}, number={7}, journal={Green Chemistry}, author={Gaspar, A. R. and Gamelas, J. A. F. and Evtuguin, D. V. and Neto, C. P.}, year={2007}, pages={717–730} }
 @inbook{lucian_argyropoulos_adamopoulos_gaspar_2007, title={Chemicals & energy from forest biomass: A review}, volume={954}, ISBN={9780841239814}, DOI={10.1021/bk-2007-0954.ch001}, abstractNote={There are approximately 89 million metric tonnes of organic chemicals and lubricants produced annually in the United States (1). The majority of these are fossil fuel-based materials that have the potential to become environmental pollutants during use and that carry end-of-life cycle concerns such as disposal, pollution, and degradation. As a result, the need to decrease pollution caused by petrochemical usage is currently impelling the development of green technologies. It is virtually inarguable that the dwindling hydrocarbon economy will eventually become unsustainable. The cost of crude oil continues to increase, while agricultural products see dramatic decreases in world market prices. These trends provide sufficient basis for renewed interest in the use of biomass as a feedstock and for the development of a lignocellulosic-based economy as the logical alternative to fossil fuel resources.}, booktitle={Materials, chemicals and energy from forest biomass}, publisher={Washington, DC: ACS Books}, author={Lucian, A. L. and Argyropoulos, Dimitris and Adamopoulos, L. and Gaspar, A. R.}, year={2007}, pages={2–30} }
 @article{guerra_gaspar_contreras_lucia_crestini_argyropoulos_2007, title={On the propensity of lignin to associate: A size exclusion chromatography study with lignin derivatives isolated from different plant species}, volume={68}, ISSN={["0031-9422"]}, DOI={10.1016/j.phytochem.2007.05.026}, abstractNote={Despite evidence that lignin associates under both aqueous and organic media, the magnitude and nature of the underlying driving forces are still a matter of discussion. The present paper addresses this issue by examining both solution properties and size exclusion behaviour of lignins isolated from five different species of softwoods, as well as from the angiosperms Eucalyptus globulus and wheat straw. This investigation has used the recently described protocol for isolating enzymatic mild acidolysis lignin (EMAL), which offers lignin samples highly representative of the overall lignin present in the wood cell wall. The molecular weight distributions of these EMALs were found to be dependent upon the wood species from which they were isolated and upon the incubation conditions used prior to size exclusion chromatography. While the chromatograms of EMALs isolated from softwoods displayed a bimodal behaviour, the elution profiles of EMAL from E. globulus and straw were nearly unimodal. A marked tendency to dissociate prevailed under incubation at room temperature for all examined species with the exception of the straw lignin preparation; furthermore, lignin solutions incubated at 4 degrees C showed an associative behaviour manifested by an increase in the weight and number average molecular weights for some species. The extent of such association/dissociation, as well as the time needed for the process to reach completion, was also found to depend upon the wood species, i.e. lignins from softwoods were found to associate/dissociate to a greater extent than lignins from E. globulus and straw. The origin of such effects within the lignin structure is also discussed.}, number={20}, journal={PHYTOCHEMISTRY}, author={Guerra, Anderson and Gaspar, Armindo R. and Contreras, Soffa and Lucia, Lucian A. and Crestini, Claudia and ArgyropouloS, Dimitris S.}, year={2007}, month={Oct}, pages={2570–2583} }
 @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{lucia_argyropoulos_adamopoulos_gaspar_2006, title={Chemicals and energy from biomass}, volume={84}, ISSN={["1480-3291"]}, DOI={10.1139/V06-117}, abstractNote={ Approximately 89 million metric tonnes of organic chemicals and lubricants are produced annually in the United States (T.M. Carole, J. Pellegrino, and M.D. Paster. Appl. Biochem. Biotechnol. 115, 871 (2004)). The majority of these materials are fossil fuel based and may load the environment during use and at the end of their life cycle. Issues, such as disposal, pollution, and degradation, must be considered and weighed. As a result, the need to decrease pollution caused by petrochemical usage is currently impelling the development of green technologies. It is virtually inarguable that the dwindling hydrocarbon economy will eventually become unsustainable. The cost of crude oil continues to increase, while agricultural products see dramatic decreases in world market prices. These trends provide sufficient basis for renewed interest in the use of biomass as a feedstock and for the development of a carbohydrate-based economy as the logical alternative to fossil fuel resources.Key words: biomass, biochemicals, natural products, bioenergy. }, number={7}, journal={CANADIAN JOURNAL OF CHEMISTRY}, author={Lucia, Lucian A. and Argyropoulos, Dimitris S. and Adamopoulos, Lambrini and Gaspar, Armindo R.}, year={2006}, month={Jul}, pages={960–970} }
 @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 31P 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, CH2CH2OH) 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{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} }