AbstractThe copolymerizations ofp‐substituted phenyl vinyl sulfides (M2) having OCH3, CH3, H, Cl, and Br substituents with styrene and methyl methacrylate (M1) and their intercopolymerizations at 60°C. were studied. From the results of copolymerizations with styrene and methyl methacrylate, the monomer reactivity ratios and theQ2e2values were determined. For example, theQandevalues for unsubstituted phenyl vinyl sulfide were 0.45 and −1.26 in the copolymerization with methyl methacrylate. This result indicated the importance of the 3dorbital resonance between the sulfur atom and the adjacent carbon atom in the transition state of copolymerizations. The relative reactivities of these monomers toward the polymer radicals were found to be correlated with the Hammett σ constants of the substituents. In the intercopolymerizations of these monomers, it was also found that the relative reactivities followed the Hammett equation approxim