Kinetics of Phase Transitions and Chemical Reactions in Gels

本研究将研究不同交联程度的物理、化学凝胶和预凝胶支化聚合物的相分离动力学。物理凝胶的工作将集中在同时相分离和聚集/凝胶在控制通过热淬火或溶剂交换制备的聚合物膜的形态方面的作用。化学交联凝胶的研究将主要集中在网络弹性和交联对相分离动力学的影响，通过成核、生长和spinodal分解机制。基于线性和非线性理论的旋多分解动力学的理论工作也将进行。提出了一种新的SAXS实验来确定沉淀颗粒尺寸的增长，以测试通常被认为是导致凝胶中列钢带形成的成核和生长机制的适用性，并检查在不稳定性导致固定模式形成的条件下的反应，称为图灵模式。这项工作具有基础和实际意义，因为相分离机制在决定复合材料的性能方面起着重要作用。凝胶为研究扩散控制反应提供了一个有用的模型系统，这对化学和生物系统中的广泛现象具有重要意义。＊＊＊

Bansil 9618467 This research will investigate the kinetics of phase separation in physical and chemical gels and pre-gel branched polymers with varying degrees of crosslinking. The work with the physical gels will focus on the role of simultaneous phase separation and aggregation/gelation in controlling the morphology of polymeric membranes prepared either via thermal quenching or solvent exchange. The studies with chemically crosslinked gels will focus on the effects of network elasticity and crosslinking on the phase separation kinetics via the mechanisms of nucleation and growth and spinodal decomposition. Theoretical work based on both linear and non-linear theory of spinodal decomposition kinetics will also be done. A novel SAXS experiment is proposed to determine the growth in the size of the precipitated particles in order to test the applicability of nucleation and growth mechanisms which are generally believed to be responsible for the formation of Liesgang bands in gels, and to examine reactions under conditions where instabilities lead to the formation of stationary patterns, known as Turing patterns. %%% This work has both fundamental and practical implications, since phase separation mechanisms play an important role in determining the properties of composite materials. Gels provide a useful model system to investigate diffusion controlled reactions, which has implications for a wide range of phenomena in chemical and biological systems. ***