Stereospecific Hydroxyl–Yne Click Polymerization to Selectively Construct High-Performance Plastics and Elastomers

Abstract

Introducing stereodefined carbon–carbon double bonds into polymeric backbone represents a powerful strategy to regulate the physical and mechanical performance of the resulting materials. Hydroxyl–yne click polymerization has recently emerged as a promising approach for constructing unsaturated polymers, while control over their stereochemistry remains a challenge. Herein, we report a simple and efficient pathway to construct unsaturated poly(vinyl ether ester)s (PVEEs) with absolute control over alkene stereochemistry through hydroxyl–yne click polymerization of trans- or cis-2-butene-1,4-diol as monomer with activated alkynes under mild polymerization conditions. By regulating the alkene stereochemistry, the resultant PVEEs exhibit tunable thermal and mechanical properties, evolving from robust thermoplastics with an ultimate tensile strength of up to 21.6 MPa to tough elastomers with up to 86% elastic recovery. Meanwhile, trans-PVEEs demonstrate superior barrier properties compared to the cis-analogues, which even could be comparable with commercial available polyethylene terephthalate and poly(l-lactide). Importantly, chemical depolymerization of the resultant PVEEs can be accomplished using a binary catalyst system of tetrabutyl titanate and 1,5,7-triazabicyclo[4.4.0]dec-5-ene to selectively recycle the diols and generate functionalized diesters in good to excellent yields.