Appaw Collins, Gilbert Richard D, Khan Saad A, Kadla John F
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA.
Biomacromolecules. 2007 May;8(5):1541-7. doi: 10.1021/bm0611681. Epub 2007 Apr 26.
The effect of increasing water composition on the rheological and microstructural behavior of a ternary cellulose acetate (CA)/N,N-dimethylacetamide (DMA)/water system is examined. Addition of water to the CA/DMA system results in enhanced steady shear viscosity and dynamic viscoelastic properties and ultimately to phase-separated gel formation. The changes in dynamic rheological behavior of the system during gelation correlate well with the combined solubility parameter (delta) and, in particular, the Hansen hydrogen-bonding solubility parameter index (delta(h)) of the solvent system, suggesting hydrogen-bonding interactions may be the major route initiating the sol-gel process. For all gels studied, the elastic modulus and the critical stress to yield shifts to higher values with increasing CA concentration and/or water content. In addition, the elastic modulus exhibits a power-law behavior with water content, with the same power-law exponent observed for gels containing different CA concentrations. Addition of water leads to formation of a denser gel network, as evidenced from direct visualization of the gel microstructure through confocal microscopy.
研究了增加水的含量对三元醋酸纤维素（CA）/N，N-二甲基乙酰胺（DMA）/水体系流变学和微观结构行为的影响。向CA/DMA体系中添加水会导致稳态剪切粘度和动态粘弹性性能增强，并最终形成相分离凝胶。体系在凝胶化过程中动态流变行为的变化与溶剂体系的组合溶解度参数（δ），特别是汉森氢键溶解度参数指数（δ(h)）密切相关，这表明氢键相互作用可能是引发溶胶-凝胶过程的主要途径。对于所有研究的凝胶，随着CA浓度和/或水含量的增加，弹性模量和屈服临界应力会向更高值移动。此外，弹性模量随水含量呈现幂律行为，对于含有不同CA浓度的凝胶观察到相同的幂律指数。通过共聚焦显微镜直接观察凝胶微观结构表明，添加水会导致形成更致密的凝胶网络。
