Theoretical study of intermolecular chain transfer to polymer reactions of alkyl acrylates

Abstract

Mechanisms of intermolecular chain transfer to polymer (CTP) reactions in monomer self-initiated polymerization of alkyl acrylates, such as methyl acrylate, ethyl acrylate, and n-butyl acrylate, are studied using density functional theory calculations. Dead polymer chains with three different structures are considered, and three types of hybrid density functionals and four basis sets are used. The energy barrier and rate constant of each reaction are calculated using the transition state theory and the rigid rotor harmonic oscillator approximation. The study indicates that tertiary hydrogens of dead polymers formed by disproportionation reactions are most likely to be transferred to live polymer chains in CTP reactions. The length of the polymer chain has little effect on the calculated activation energies and transition-state geometries in all CTP mechanisms explored in this study. Moreover, CTP reactions of methyl, ethyl, and butyl acrylates have similar energy barriers and rate constants. The application of the integral equation formalism-polarizable continuum model results in higher CTP energy barriers. This increase in the predicted CTP energy barriers is larger in n-butanol than in p-xylene. However, the application of the conductor-like screening model does not affect the predicted CTP kinetic parameters.