Kinetics of Phase Transitions and Chemical Reactions in Gels

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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. ***