Radical Copolymerization Behavior of Alkyl Vinyl Sulfides

In order to clarify the effects of the sulfur atom and the alkyl groups in alkyl vinyl sulfides (RVS) on their reactivities, the radical copolymerizations of eight RVS (M₂) with styrene, methyl methacrylate, and acrylonitrile (Mi) were investigated at 60°C, and the copolymerization parameters were determined. It was found that the Q and e values for RVS were estimated as 0.3 ～ 0.5 and -1.1 ～ -1.7, respectively, from the copolymerizations with styrene, and these values were almost unchanged, regardless of the type of alkyl group in RVS. These results indicated that the electron-sharing, 3d orbital resonance between the growing radical derived from electron-donating RVS monomer and the adjacent sulfur atom was important in the transition state of copolymerizations.

It was also found that the copolymer composition curves in the copolymerizations of RVS varied widely with the comonomers used, and the tendency for alternative copolymerizations increased with an increase in the electron-accepting nature of the comonomers in the order: styrene ≤ methyl methacrylate ≤ acrylonitrile. The selectivities between RVS and alkyl vinyl ether toward various polymer radicals were determined, and they were found to correlate with the e values of the monomers corresponding to the attacking polymer radicals.