AbstractThe copolymerization of sulfur dioxide with some alkenoic acids such as acrylic, 3‐butenoic, 4‐pentenoic, and 10‐undecenoic acid was carried out using organic and aqueous media in the presence of (CH3)3 COOH/SO2 redox system. Elemental analysis, IR, and 13C‐NMR revealed that the copolymers synthesized from the acrylic acid/SO2 system were of variable composition in organic media, but only polyacrylic acid homopolymer was formed in the presence of water. The other three alkenoic acid/SO2 systems gave always polysulfone copolymers of alternating structure regardless of the experimental conditions employed. Thermal analysis (TGA and DTA) of selected samples gave Tg in the 73–101°C, range Tm between 160 and 228°C, and the total weight loss in air from 31 to 97%. Flammability decreased as the S:C mole ratio increased. NMR shows that the complexation of SO2 with the CC part of all alkenoic acids is low.