Kinetics Dependence of RAFT Emulsion Polymerization of 2-Ethylhexyl Acrylate on Initiator Concentrations

Abstract

Reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization with a well-designed amphiphilic macroRAFT agent as a surfactant has been well-developed as a powerful tool to synthesize high molecular weight multiblock copolymers. However, the polymerization kinetics research has been mostly limited to styrene polymerization. It has been reported that the dependence of the particle number on initiator concentration is described by N_p∝[I]^−0.4 in amphiphilic macroRAFT-mediated emulsion polymerization of styrene, which surprisingly deviates from the classical Smith–Eward equation. In the current study, the dependence of polymerization kinetics on the initiator concentration in the RAFT emulsion polymerization of 2-ethylhexyl acrylate (EHA) is investigated. It is revealed that the dependence of the particle number on initiator concentration (N_p∝[I]^−0.29) is similar to that of styrene but the exponent is less. Additionally, compared to styrene polymerization, the inhibition period in EHA polymerization is significantly extended due to the much lower water-solubility of EHA.