Study on two different dithiobenzoates effectiveness in bulk RAFT polymerization of β-myrcene.

Abstract The study aimed to evaluate the impact of two chain transfer controllers, ethyl 2-(phenylcarbonothiolthio)-2-phenylacetate (EPPA) and 2-(4-methoxyphenylcarbonothiolthio) ethanoic acid (MPEA), from the dithioester family (dithiobenzoates), on the RAFT polymerization of β-myrcene. The initiators employed were azobisisobutyronitrile (AIBN) or dicumylperoxide (DCP), at 65°C and 90°C, respectively. The study analyzed the impact of the type of controller, temperature, and initiator/controller ratio on the living nature of β-myrcene polymerization. The results showed that with an increase in the initiator/controller ratio, the rate of polymerization increased, but the obtained molar masses decreased. The MPEA controller showed better performance in controlling the termination and chain transfer reactions, especially when AIBN was used as the initiator. A rise in polymerization temperature led to a loss in the control of polymerization, causing an increase in the degree of polydispersity due to the presence of transfer reactions. The most effective control in the RAFT polymerization of β-myrcene was achieved using MPEA as the controller and AIBN as the initiator, resulting in a poly(β-myrcene) with 87% 1,4-addition according to proton NMR analyses and a polydispersity of 1.27 by gel permeation chromatography (GPC). Finally, the study synthesized a poly(β-myrcene)-bpoly(styrene) block copolymer with low polydispersity (Ð1.1) by sequentially adding styrene to the previously synthesized MPEApoly(β-myrcene)-based RAFT macrocontroller.