@article{shankar_klossner_weaver_koga_zanten_krause_colina_tanaka_spontak_2009, title={Competitive hydrogen-bonding in polymer solutions with mixed solvents}, volume={5}, ISSN={["1744-683X"]}, DOI={10.1039/b808479c}, abstractNote={Poly(ethylene oxide) (PEO) coil size is investigated in a binary mixture of solvent molecules capable of cooperatively hydrogen-bonding with each other, as well as with the PEO chains. Viscometry reveals a minimum in zero shear rate solution viscosity at a molar ratio of ∼2:1 water:methanol. This viscosity coincides with a minimum in PEO gyration radius and occurs near the conditions where water/methanol mixtures deviate most markedly from ideal solution behavior. A minimum in polymer mean square end-to-end distance is predicted for polymer solutions composed of two hydrogen-bonding solvents.}, number={2}, journal={SOFT MATTER}, author={Shankar, Ravi and Klossner, Rebecca R. and Weaver, Juan T. and Koga, Tsuyoshi and Zanten, John H. and Krause, Wendy E. and Colina, Coray M. and Tanaka, Fumihiko and Spontak, Richard J.}, year={2009}, pages={304–307} }
 @article{klossner_queen_coughlin_krause_2008, title={Correlation of Chitosan's Rheological Properties and Its Ability to Electrospin}, volume={9}, ISSN={["1525-7797"]}, DOI={10.1021/bm800738u}, abstractNote={Chitosan-based, defect-free nanofibers with average diameters ranging from 62 +/- 9 nm to 129 +/- 16 nm were fabricated via electrospinning blended solutions of chitosan and polyethylene oxide (PEO). Several solution parameters such as acetic acid concentration, polymer concentration, and polymer molecular weight were investigated to optimize fiber consistency and diameter. These parameters were evaluated using the rheological properties of the solutions as well as images produced by scanning electron microscopy (SEM) of the electrospun nanofibers. Generally, SEM imaging demonstrated that as total polymer concentration (chitosan + PEO) increased, the number of beads decreased, and as chitosan concentration increased, fiber diameter decreased. Chitosan-PEO solutions phase separate over time; as a result, blended solutions were able to be electrospun with the weakest electric field and the least amount of complications when solutions were electrospun within 24 h of initially being blended. The addition of NaCl stabilized these solutions and increased the time the blended solutions could be stored before electrospinning. Pure chitosan nanofibers with high degrees of deacetylation (about 80%) were unable to be produced. When attempting to electrospin highly deacetylated chitosan from aqueous acetic acid at concentrations above the entanglement concentration, the electric field was insufficient to overcome the combined effect of the surface tension and viscosity of the solution. Therefore, the degree of deacetylation is an extremely important parameter to consider when attempting to electrospin chitosan.}, number={10}, journal={BIOMACROMOLECULES}, author={Klossner, Rebecca R. and Queen, Hailey A. and Coughlin, Andrew J. and Krause, Wendy E.}, year={2008}, month={Oct}, pages={2947–2953} }