Theoretical Study of Chain Transfer to Agent Kinetics in Butyl Acrylate Polymerization

Reactions of chain transfer to agent (CTA) are conventionally used to regulate the polymer molecular weight during radical polymerization processes, due to the interaction between CTAs and chain-end growing radicals. In acrylate polymerization, the presence of a relatively large amount of midchain radicals (MCRs) opens the way for alternative kinetic pathways involving CTAs, which can result in a modification of the overall kinetics as well as the final polymer properties. In this work, chain transfer reactions from butyl acrylate (BA) radicals of various size and nature to a set of selected CTAs are investigated using quantum chemistry. The different reactivity of chain-end and midchain radicals is emphasized, with particular focus on the kinetic effect of the radical chain length. Eventually, the mechanism of MCR patching and its relevance in decreasing the branching density are critically examined, with reference to the estimated kinetic parameters and experimental evidence about BA polymerization.