Recyclable Vinyl-Functionalized Polyesters via Chemoselective Organopolymerization of Bifunctional α-Methylene-δ-Valerolactone

alpha-Methylene-delta-valerolactone (MVL) is a bifunctional monomer comprising of a highly stable six-membered delta-valerolactone ring and highly reactive C(sic)C bond. Previously, the vinyl-addition polymerization (VAP) product, namely P(MVL)(VAP), has been formed exclusively. In this study, this conventional chemoselectivity is reversed, wherein organic catalysts are used to enable the first ring-opening polymerization (ROP) of MVL, exclusively affording a metal-free, unsaturated polyester, namely P(MVL)(ROP). This challenging goal is achieved by investigating different catalysts, initiators, and reaction conditions. In addition, the formation of two polymers, namely P(MVL)(ROP) and P(MVL)(VAP), is easily regulated by varying the polymerization solvent. The resulting P(MVL)(ROP) can be easily post-functionalized to form crosslinked or sulfurized materials; notably, it can be almost completely converted into its monomer thermochemically.