Sustainable poly(ε-decalactone)−poly(l-lactide) multiarm star copolymer architectures for thermoplastic elastomers with fixed molar mass and block ratio

Abstract

To improve the thermal and mechanical properties of thermoplastic elastomers derived from plant-based monomers, a series of well-defined multiarm star block copolymers was investigated. Controlled bulk ring-opening polymerization of ε-decalactone (DL) with multiarm initiators yielded hydroxyl-terminated (PDL−OH)n, which were subsequently converted to (PDL−PLLA)n using l-lactide (LLA) through a one-pot, two-step process. The multiarm copolymers were designed for targeting on Mn,NMR and fPLLA of 180 kg mol−1 and 0.27, respectively. Structural analysis proved that PLLA hard domains were thinner, and thus, more compact microphase-separated structures with hexagonally packed cylinders were induced by increasing n. Thermal and tensile property measurement demonstrated that, although the copolymers had a lower crystallinity in PLLA due to the shorter chain length, the thermal degradation stability and mechanical strength were enhanced, which was caused by to an amplified pinning effect caused by the more closed packed PLLA domains, in addition to chemical crosslinking of the PDL strands.