Turning Readily Available Acrylates into Cyclic Xanthates for Radical Ring-Opening Polymerizations

Abstract Cyclic sulfur-containing monomers represent a promising class of comonomers for radical ring-opening polymerization, but only a limited number of examples have been reported to date. Here, the cyclic xanthate tert-butyl 2-thioxo-1,3-oxathiolane-5-carboxylate (Oxa) was synthesized from readily available tert-butyl acrylate via epoxidation and subsequent ring extension with carbon disulfide. While homopolymerization was not observed, efficient copolymerization with vinyl acetate yielded copolymers containing dithiocarbonate units in the polymer backbone. Reactivity ratio analysis revealed a preference for heteropropagation, enabling efficient incorporation of dithiocarbonate units with Oxa contents of up to 40 mol %, at which compositions the copolymers displayed a tendency toward an alternating microstructure. The resulting copolymers were highly transparent and colorless and exhibited molar masses and glass transition temperatures comparable to those of poly(vinyl acetate). The incorporated dithiocarbonate units enabled selective backbone cleavage by aminolysis, base-mediated hydrolysis, or oxidative degradation, whereas acidic conditions (0.5 M HCl) did not affect the polymers. Copolymers containing at least 25 mol % Oxa generated low-molar-mass degradation products, confirming the efficient incorporation of degradable units into the polymer chains. These results establish cyclic xanthates derived from a readily accessible acrylate precursor as a versatile platform for introducing chemically degradable dithiocarbonate functionalities into vinyl acetate-based polymers.