@article{sullivan_tang_kennedy_talwar_khan_2014, title={Electrospinning and heat treatment of whey protein nanofibers}, volume={35}, ISSN={["1873-7137"]}, DOI={10.1016/j.foodhyd.2013.07.023}, abstractNote={The ability to develop nanofibers containing whey proteins presents a unique opportunity to exploit the inherent benefits of whey protein with that of the desirable attributes of nanofibers. In this study, aqueous whey protein solutions, both whey protein isolate (WPI) and one of its major components beta-lactoglobulin (BLG), are electrospun into nanofibers in conjunction with a spinnable polymer, poly(ethylene oxide) (PEO). WP:PEO solution composition as high as 3:1 and with average fiber diameters ranging from 312 to 690 nm are produced depending on polymer composition and concentration. WP/PEO solutions are also successfully electrospun at acidic pH (2 ≤ pH ≤ 3), which could improve shelf life. FTIR analysis of WP/PEO fiber mat indicates some variation in WP secondary structure with varying WPI concentration (as WPI increases, % α-helix increases and β-turn decreases) and pH (as pH decreases from neutral (7.5) to acidic (2), % β-sheet decreases and α-helix increases). XPS also confirms the presence of WP on the surface of the blend fibers, augmenting the FTIR analysis. Interestingly, WP/PEO composite nanofibers maintain its fibrous morphology at temperatures as high as 100 °C, above the 60 °C PEO melting point. In addition, the mats swell in water and retain a fibrous quality which makes them desirable for application in regenerative medicine. Finally, we incorporate a small hydrophobic molecule Rhodamine B (RhB) as a model flavonoid into WP/PEO nanofiber mats. The BLG:PEO nanofibers qualitatively exhibit improved fiber quality and RhB distribution compared to PEO nanofibers; however, no effect on the release profile is observed.}, journal={FOOD HYDROCOLLOIDS}, author={Sullivan, Stephanie T. and Tang, Christina and Kennedy, Anthony and Talwar, Sachin and Khan, Saad A.}, year={2014}, month={Mar}, pages={36–50} }
 @article{talwar_krishnan_hinestroza_pourdeyhimi_khan_2010, title={Electrospun Nanofibers with Associative Polymer-Surfactant Systems}, volume={43}, ISSN={["1520-5835"]}, DOI={10.1021/ma1013447}, abstractNote={Associative polymers are unique in their structure with pendant hydrophobes attached to their hydrophilic backbone, enabling associations between the hydrophobes and forming junctions in aqueous solutions. In this study, we examine efforts to produce electrospun nanofibers of associative polymers in conjunction with a readily spinnable polymer. Scanning electron micrograph (SEM) images reveal that the solution rheology sets an upper limit to the concentration of associative polymer that can be successfully electrospun. However, addition of nonionic surfactants to the precursor solution results in significant improvement in nanofiber morphology as evinced from reduced beading. Through judicious use of nonionic surfactants to modulate solution viscoelastic properties, we are able to obtain defect-free nanofiber morphology and gain new insights into the fundamentals of the electrospinning process. In particular, we find that solution viscoelasticity as measured in terms of the relaxation time, rather than viscosity as typically hypothesized, controls the nanofiber formation process.}, number={18}, journal={MACROMOLECULES}, author={Talwar, Sachin and Krishnan, Arjun S. and Hinestroza, Juan P. and Pourdeyhimi, Behnam and Khan, Saad A.}, year={2010}, month={Sep}, pages={7650–7656} }
 @article{talwar_harding_oleson_khan_2009, title={Surfactant-Mediated Modulation of Hydrophobic Interactions in Associative Polymer Solutions Containing Cyclodextrin}, volume={25}, ISSN={["0743-7463"]}, DOI={10.1021/la803056e}, abstractNote={The ability of nonionic surfactants to modulate the rheological characteristics of comblike hydrophobically modified associative polymer solutions containing cyclodextrin (CD) is examined. Addition of either alpha- or beta-CD to these polymers results in a marked decrease in solution viscosity and viscoelastic properties because of the encapsulation of the polymer hydrophobes by CD. Nonionic surfactants, introduced to such a system, alter the hydrophobic interactions by competing with the polymer hydrophobes for complexation with the CDs. In this regard, nonylphenol ethoxylates (NPe) with different ethylene oxide chain lengths, which determine the hydrophilic-lipophilic balance (HLB) of the surfactant, are used. Our results reveal that the extent and rate of recovery of zero shear viscosity as well as dynamic moduli are strongly influenced by the type of CD (alpha versus beta) as well as the HLB of the surfactant. For polymer solutions containing alpha-CD, recovery is observed solely in the presence of a low-HLB surfactant (NP6 and NP8). Additionally, in the case of NP6, the viscosity increases monotonically above the original hydrophobically modified alkali-soluble emulsion viscosity with surfactant addition, whereas for that of a higher HLB surfactant (NP15), the viscosity shows no appreciable change. In the case of beta-CD, on the other hand, a complete recovery as well as further enhancement of rheological properties is achieved using the above surfactants. However, the trends of viscosity modulation are dissimilar for different surfactants as we witness a monotonous increase in the case of NP6 while a maximum in viscosity is observed in the presence of NP8 and NP15. The contrasting observations can be explained in terms of varying affinities of alpha- and beta-CDs to bind with NP surfactants and the existence of different micellar structures in solution as governed by surfactant HLB. These results are further confirmed by UV/vis spectroscopy and cloud point measurements.}, number={2}, journal={LANGMUIR}, author={Talwar, Sachin and Harding, Jonathon and Oleson, Keith R. and Khan, Saad A.}, year={2009}, month={Jan}, pages={794–802} }
 @article{talwar_hinestroza_pourdeyhimi_khan_2008, title={Associative polymer facilitated electrospinning of nanofibers}, volume={41}, ISSN={["1520-5835"]}, DOI={10.1021/ma8004795}, abstractNote={Electrospun nanofibers present an exciting avenue for development of novel materials with well-defined functionalities; however, broadening the scope of electrospinning to a diverse range of polymers remains a major challenge. In particular, a recurring issue in this field is the inability to spin polymers at lower concentrations in order to achieve smaller fiber diameters. This work explores the use of associative polymers as a means to overcome this limiting factor that prevents the electrospinnning of nanofibers from low-concentration polymer solutions. Hydrophobically modified alkali-soluble emulsion (HASE) polymers are comblike associative polymers with pendant hydrophobes that form a network in aqueous media consisting of both intra- and intermolecular hydrophobic junctions. Rheological measurements reveal that addition of HASE polymers in small amounts to poly(ethylene oxide) solutions leads to considerable increase in viscosity as well as dynamic moduli of the system. More importantly, these rheol...}, number={12}, journal={MACROMOLECULES}, author={Talwar, Sachin and Hinestroza, Juan and Pourdeyhimi, Benham and Khan, Saad A.}, year={2008}, month={Jun}, pages={4275–4283} }
 @article{talwar_scanu_raghavan_khan_2008, title={Influence of binary surfactant mixtures on the rheology of associative polymer solutions}, volume={24}, ISSN={["0743-7463"]}, DOI={10.1021/la801030n}, abstractNote={Hydrophobically modified alkali-soluble emulsion polymers (HASE) are a class of comblike associative polymers that can impart high viscosities to aqueous solutions. The rheology of HASE solutions can be tuned by the addition of surfactants, such as nonylphenol ethoxylates (NP e), where e is the length of the hydrophilic (ethoxylate) chain. While previous studies have considered individual surfactants, our focus here is on binary surfactant mixtures. We find that equimolar NP4-NP12 mixtures significantly enhance the zero-shear viscosities of HASE solutions as compared to equivalent amounts of NP8, especially at high overall surfactant concentrations. Dynamic rheological measurements suggest that the higher viscosities are due to increases in the lifetime of hydrophobic junctions in the polymer-surfactant network. In contrast to the above results, equimolar NP4-NP8 mixtures are rheologically identical to equivalent solutions of NP6. The differences between the two sets of mixtures are further correlated with cloud point measurements and thereby with the overall hydrophilic-lipophilic balance (HLB) of the surfactant system.}, number={15}, journal={LANGMUIR}, author={Talwar, Sachin and Scanu, Lauriane and Raghavan, Srinivasa R. and Khan, Saad A.}, year={2008}, month={Aug}, pages={7797–7802} }
 @article{talwar_scanu_khan, title={Hydrophobic interactions in associative polymer/nonionic surfactant systems: Effects of surfactant architecture and system parameters}, volume={50}, number={6}, journal={Journal of Rheology (New York, N.Y.)}, author={Talwar, S. and Scanu, L. F. and Khan, S. A.}, pages={831–847} }