Copolymerization of simple methacrylates by Cu(0)-mediated reversible deactivation radical polymerization

Abstract

This study examined the kinetics of copolymerization of two different simple model monomers, methyl methacrylate (MMA), and ethyl methacrylate (EMA), via Cu(0)-mediated reversible deactivation radical polymerization (RDRP), where the reactivities of MMA and EMA are expected to be nearly equal, and therefore, random copolymerization is favored. In these kinetic studies, the apparent propagation rate constants and induction periods with variations in the feed ratio and polymerization temperature were estimated. The reactivity ratios determined based on the kinetic studies were close to unity. In addition, the reactivities of MMA and EMA radicals to both monomers were evaluated by determining the thermodynamic parameters of the activation processes; the reactions of active species with two different monomers experience slightly different enthalpic barriers but almost zero entropic contributions, strongly suggesting that the copolymerization provides an almost, but not perfectly, random sequence and providing a clear chemical picture of the propagation reaction that occurs during copolymerization. The glass transition studies of synthesized P(MMA-r-EMA) highlight the significance of the kinetic information to predict the glass transition temperature in a copolymer system realized by Cu(0)-mediated RDRP. The current study provides a deeper understanding of the fundamental aspects and a tool to gain insight into copolymerization via RDRP, which are ultimately correlated with various physical and chemical properties. Copolymerization kinetics of methyl methacrylate and ethyl methacrylate by Cu(0)-mediated reversible deactivation radical polymerization was thoroughly explored. The copolymerization follows pseudo-first order kinetics in a highly controlled manner. Detailed kinetic studies revealed that two different monomers experience different enthalpic barriers in propagation, which strongly suggest that the copolymerization exhibits not perfectly, but nearly random composition. Further studies on glass transition and chain extension highlight the significance of these fundamental studies to predict thermal properties and to realize complex polymer architecture.