A Potential Biobased Thermoplastic Elastomer based on β-Myrcene via RAFT-mediated Miniemulsion Polymerization

In recent times, there has been an increasing focus on utilizing bioresources in polymer synthesis owing to their numerous advantages over petroleum-based polymers. Among the various types of polymers, thermoplastic elastomers (TPEs) have garnered considerable interest due to their ease of processing and ability to be recycled and reused. β-Myrcene (MY), a terpene compound, is a crucial substituted-diene monomer with a backbone comprising a conjugated diene, resembling the isoprene unit found in natural rubber. MY can be sourced from various bioresources. In this study, the reversible addition-fragmentation chain-transfer (RAFT) polymerization was used to prepare a new ABA-type triblock copolymer named poly(isobornyl methacrylate)-b-poly(β-myrcene)-b-poly(isobornyl methacrylate) (IMI). In this fully bio-derived triblock copolymer, poly(isobornyl methacrylate) (PIBMA) and poly(β-myrcene) (PMY) act as the hard block and the soft block, respectively. Initially, IBMA was polymerized using S,S-dibenzyl trithiocarbonate, a bifunctional RAFT agent. Subsequently, the obtained PIBMA served as a macro-RAFT agent for the miniemulsion polymerization of MY, resulting in the formation of the IMI triblock copolymers. The successful synthesis of the block copolymers (BCPs), their composition, and molecular weight were confirmed through FTIR, NMR, and GPC analyses. Additional investigation employing AFM in combination with DSC unveiled the phase-separated morphology of the rigid and flexible domains attributed to PIBMA and PMY, respectively. The IMI BCPs exhibited favorable tensile properties, with their scraps demonstrating effective reprocessiblity and reuse, underscoring their potential as sustainable TPE materials.