Merging CO2-Based Building Blocks with Cobalt-Mediated Radical Polymerization for the Synthesis of Functional Poly(vinyl alcohol)s

Abstract

The use of CO2-based α-alkylidene cyclic carbonates in controlled radical polymerization has so far not been exploited, despite the fact that the cyclic carbonate ring offers a multitude of possible modifications. Herein, the synthesis of well-defined copolymers of vinyl acetate (VAc) and 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one (DMMDO) using cobalt-mediated radical polymerization (CMRP) at 40 °C is reported. The controlled nature of the polymerization was confirmed while molecular weights of up to 25 000 g mol–1 and narrow dispersities (<1.4) were obtained. The copolymer structure was elucidated combining NMR, FT-IR, and MALDI-TOF analyses and consists of a polymer backbone with pendant carbonate rings. Further insights into the copolymer structure were gained through the monomers’ reactivity ratios, and a homogeneous distribution of the DMMDO monomer along the polymer chain was observed. A highly water-soluble poly(vinyl alcohol)-based copolymer was obtained by basic hydrolysis, whereas the chemoselective acidic hydrolysis of the acetate groups left the cyclic carbonate rings untouched, which were then exploited for further postmodification with amines. The precise copolymerization of VAc with CO2-sourced five-membered cyclic carbonates bearing an exomethylene moiety is therefore a powerful tool for the synthesis of new variants of poly(vinyl alcohol)-based copolymers.