One-Step Synthesis of a Degradable Thermoplastic Elastomer with Gradient Sequence via Chiral Brønsted Acid-Mediated Cationic Copolymerization of Vinyl Ether Monomer Mixtures

This contribution presents the facile synthesis of a new carbon-backbone thermoplastic elastomer (TPE) with on-demand degradability via one-step cationic copolymerization from biorenewable isobutyl vinyl ether (iBVE) and 2,3-dihydrofuran (DHF) monomer mixtures. The utilization of imidodiphosphorimidate (IDPi), a strong organic Brønsted acid featuring a highly sterically demanding chiral pocket, as a single-component organic catalyst is the key to this achievement, which can bias the polymerization reactivity of comonomers, allow the copolymerization to proceed in a relatively controlled way, and render isotactic enchainment for the iBVE comonomer. Accordingly, DHF exhibits a much faster polymerization rate than iBVE during the copolymerization as opposed to their homopolymerizations (iBVE ≫ DHF), and a series of DHF/iBVE gradient copolymers with a hard (DHF-rich)–soft (iBVE-rich)–hard (neat-isotactic PiBVE) structure have been conveniently synthesized using a one-step approach. Structure–property evaluations reveal that the gradient copolymer, obtained by the copolymerization with a [DHF]0/[iBVE]0 feed ratio of 2000:6000, possesses good thermal (Td = 309 °C, Tm ≈ 70 °C, Tg ≈ −16 to 30 °C) and elastomeric properties (σB = 5.73 MPa, εB = 880%) and yet is capable of degrading in the presence of Fenton reagent, thus successfully constructs a new carbon-backbone TPE with high performance and on-demand degradability for the first time from poly(vinyl ether)-based gradient copolymers.