Polymerization of α-vinyl cyclic sulfones

Abstract

$\alpha$-Vinyl cyclic sulfones, 2-vinylthiolane-1,1-dioxide, 2-vinylthiane-1,1-dioxide, 2-vinylthiepane-1,1-dioxide, 3,3-diethoxy-2-vinylthietane-1,1-dioxide, 2-phenyl-5-vinylthiolane-1,1-dioxide, 2-methyl-2-vinylthiolane-1,1-dioxide, 2-allyl2-vinylthiolane-1,1-dioxide, and 2-benzyl-2-vinylthiolane-1,1-dioxide have been synthesized, and their radical polymerization behavior under various conditions and the properties of the resulting polymers were investigated. Those eight $\alpha$-vinyl cyclic sulfone compounds exhibited quite different polymerization behaviours depending upon their structures. 2-Vinylthiolane-1,1-dioxide polymerized radically well and cleanly via quantitative ring-opening. The resulting polymer was not soluble in ordinary organic solvents, but soluble in trifluoroacetic acid and concentrated sulfuric acid. NMR and IR spectra of monomer and polymer confirmed their structures, and the resulting polymer was confirmed to be poly(sulfonyl-hex-2-enylene). 2-Vinylthiane-1,1-dioxide and 2-vinylthiepane were synthesized and polymerized radically under various conditions. Structures confirmed by NMR and IR spectra of polymers from both of the monomers indicated that some of the monomer molecules underwent polymerization without ring-opening. Each monomer seemed to have different reasons for the tendency of partial ring-opening; ring-stability for a sixmembered monomer, and conformational effect for a seven-membered monomer. 3,3-Diethoxy-2-vinylthietane-1,1-dioxide was also prepared. However, all the attempts for the polymerization failed. 2-Phenyl-5-vinylthiolane-1,1-dioxide was synthesized and subjected to polymerization, but it did not show any sign of polymerization. Three derivatives of 2-vinylthiolane-1,1-dioxide were also synthesized and polymerized. Only methyl derivative gave small yield of polymer, and allyl or benzyl derivatives were found to be resistant to polymerization. 2-Vinylthiolane-1,1-dioxide copolymerized with certain comonomers suc...