Radical thiocarbonyl addition-ring-opening (TARO) copolymerisation offers a promising route for incorporating weak linkages into vinyl-based polymers, enabling their controlled degradation. Expanding the scope of this method, researchers have developed a novel cyclic xanthate monomer, 4_H_-1,3-benzoxathiin-2-thione (BOT), which features an additional in-ring sulfur atom. The monomer was synthesised via reaction of 2-mercaptobenzyl alcohol with thiophosgene, avoiding thionation reactions commonly used for similar monomers.
BOT was polymerised using an AIBN-initiated radical mechanism, achieving a 37 % conversion rate. Importantly, approximately 75 mol% of the BOT units underwent ring-opening, forming dithiocarbonate repeat units alongside ring-retained…