Thermoplastic elastomers (TPEs) are a class of exceptional polymers. They can show thermoplastic as well as elastomeric properties at the same time and thus can easily be processed, recycled, and reused. In recent times, polymers prepared from bio-resources have been able to attract a great deal of attention because of their green and sustainable background. Terpenes are recognized to be the largest group of natural products and some of them can be used as monomers for polymerization. They are found in several essential oils of many types of plants and flowers, insects, and marine organisms. β-Myrcene (MY), a terpene vinylic monomer, carries the same backbone as that of an isoprene unit, the building unit of natural rubber, and many other synthetic polymers. Because of this very reason, several efforts have been made and reported to synthesize elastomers and elastomeric materials based on MY. In this work, reversible addition-fragmentation chain-transfer (RAFT) polymerization was used to prepare an ABA type triblock copolymer polystyrene-b-poly(β-myrcene)-b-polystyrene (SMS). The poly(β-myrcene) block acted as the soft domain and the polystyrene blocks as the hard domain of the potential TPE. NMR, FTIR & GPC analyses confirmed the successful preparation of the block copolymers (BCPs). Phase-separated morphology of the hard and soft domains for the BCPs was observed via DSC & AFM analyses. The SMS BCPs exhibited a maximum tensile strength of 3.4 MPa and elongation at break of 625 % with a remarkably low tension set of 4.12 %. Scrapes of the SMS BCPs were also recycled and reused successfully. All of these indicate the potential applicability of the synthesized BCPs as a TPE.

Synthesis of a bio-based Thermoplastic elastomer via RAFT polymerization

Mr. Uddhab Kalita Senior Research Fellow

Indian institute of Technology Kharagpur

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