Tailoring the Properties of Polyhydroxyalkanoates from Plastics to Elastomers via Stereoselective Copolymerizations of rac-β-Butyrolactone and β-Propiolactone

Poly(3-hydroxybutyrate), a crucial member of the large biodegradable polyhydroxyalkanoate family, suffers from its brittleness. To enhance its performance, we employed a straightforward approach involving the ring-opening copolymerization of racemic-beta-butyrolactone (rac-beta-BL) and beta-propiolactone (beta-PL) using the syndio-selective amino-alkoxy-bis(phenolate)-yttrium complex as a catalyst, thanks to the excellent ductility of poly(3-hydroxypropionate). Control over the rac-beta-BL/beta-PL feeding ratios and polymerization time yielded random or block copolymers with tunable thermal and mechanical properties comparable to traditional fossil-based plastics. Furthermore, we achieved one-pot synthesis of hard-soft-hard triblock copolymers by exploiting monomers' different copolymerization rates and a bifunctional initiator, thus transforming polyhydroxyalkanoates from hard and tough plastics to soft and ductile thermoplastic elastomers.