Precision synthesis of a biobased myrcene thermoplastic elastomer by using an amphiphilic macro-RAFT agent via emulsion polymerization in aqueous medium

In recent years, myrcene has emerged as a biobased alternative to isoprene for the manufacture of thermoplastic elastomers due to its similarity to isoprene, a building block for natural rubber. Through the use of highly reactive tert-butyl acrylate as a hard segment monomer, a structurally well-defined poly(tert-butyl acrylate)-b-poly(β-myrcene)-b-poly(tert-butyl acrylate) (BMB) thermoplastic triblock copolymer elastomer was synthesized by a mild reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization method utilizing a precisely devised amphiphilic macro-RAFT agent. The block copolymer BMB was confirmed by NMR, FTIR, and GPC analyses. BMB thus exhibits typical thermoplastic elastomeric properties, as indicated by its mechanical properties with an ultimate tensile strength of 3.0 MPa and an elongation at break of 195% with tert-butyl acrylate added at 50% mass ratio. The properties of BMB can be easily tuned by adjusting the hydrolysis degree, facilitating cooperative interactions in the hard phase and enhancing tensile properties. This carboxyl interaction is an effective strategy for controlling medium strength thermoplastic elastomers.