Contributions to the quaternization description and kinetics illustrated on poly(dimethylaminoethyl methacrylate)

Abstract

Using the effects of solvent polarity observed on the microstructure of reaction products and the viscosity of the reaction medium, the evolution of the polymer chain conformation when the conversion changes, as well as the corresponding reaction kinetics, are formulated to explain the characteristics of the quaternization reaction of poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA), a polymer with flexible side-chains ended by tertiary amine groups.So, the polymeric chain is fully extended in strongly polar solvents regardless of the degree of quaternization (DQ), leading to simple kinetics of the second order. In less polar solvents, the polymer chain has coil conformation, which causes the reaction to take place more on the coil edge, which in turn leads to quaternized block formation and auto-acceleration. Self-acceleration is explained by bringing the unreacted groups to the periphery of the coil by the solvent because it prefers them in the detriment of the reacted groups. The kinetics model for self-accelerated reactions is validated by finding that the fraction of peripheral unreacted amine groups is nearly constant during the entire reaction. Such kinetics could be applied for other polymer analogous reactions when the polymer chains take coil conformation or associate with each other in globules.