Sol-gel transition and molecular dynamics in the systems based on the copolymer of methyl methacrylate with methacrylic acid

Abstract

The NMR method is used to study sol-gel transition in the system based on the copolymer of methyl methacrylate with methacrylic acid. The NMR studies showed that sol-gel transition proceeds via three stages. At the first one, diffusion of the swelling agent causes devitrification of the copolymer; simultaneously, on the macroscopic scale the aggregates of the latex particles disintegrate. At the second stage, a gel is formed that has non-equilibrium structure. The latter is rearranged during the third stage. The ratio of the rates of the processes determining these three stages depends on the concentration of the extender. Upon completion of sol-gel transition, the system is a polyphase one. It comprises highly elastic, crystalline (or vitreous), and transitional phases. NMR spectroscopy provides a way to measure the ultimate degree of compatbility of a polymer-swelling agent pair.