Biobased Thermoplastic Elastomer Based on an SMS Triblock Copolymer Prepared <i>via</i> RAFT Polymerization in Aqueous Medium
Uddhab Kalita, Sarthik Samanta, Sovan Lal Banerjee, Narayan Chandra Das, Nikhil K. Singha
Abstract
In recent years, there has been a great interest in preparing polymers from bioresources, as this practice has several advantages over petrobased polymers. Thermoplastic elastomers (TPEs) are an interesting class of polymers that can be easily processed, reused, and recycled. The terpene, β-Myrcene (MY), is an important vinylic monomer having a conjugated diene in the backbone, which has a resemblance to the isoprene unit, a building block for natural rubber. MY is available from several bioresources like hops, lemongrass, bay plants, and so forth. In this work, reversible addition–fragmentation chain-transfer (RAFT) polymerization was used for the very first time to prepare an ABA-type triblock copolymer, polystyrene-b-poly(β-myrcene)-b-polystyrene (SMS), where poly(β-myrcene) acted as the soft block and polystyrene (PS) as the hard block. For this, styrene was initially polymerized using S,S-dibenzyl trithiocarbonate as a bifunctional RAFT agent, and the resultant PS was then used as a macro-RAFT agent to polymerize MY to attain SMS triblock copolymers. The successful preparation of the block copolymers (BCPs) was confirmed by NMR, FTIR, and GPC analyses. The DSC and AFM analyses showed the phase-separated morphology of hard and soft domains of PS and PMY, respectively. These SMS BCPs showed good tensile properties and a low tension set of 4.12%, indicating their application as a potential TPE. The scrapes of these SMS BCPs were successfully recycled and reused, indicating the sustainability of the process for this potential TPE.