Cationic polymerization of styrenes by protonic acids and their derivatives, 4. Homo‐ and Co‐polymerizations of para‐substituted styrenes by CF3SO3H

Abstract p‐Methyl‐ and p‐chlorostyrenes (pMeSt and pClSt) were polymerized by CF3SO3H in methylene chloride at 0°C and gave polymers with a bimodal molecular weight distribution (MWD). This indicates that the polymerizations involve two independent propagating species: a dissociated and a non‐dissociated species. Their selectivities toward monomers were compared in the copolymerizations of pMeSt and pClSt with styrene (St) by CF3SO3H in benzene, methylene chloride, and nitrobenzene solvents. Decreasing solvent polarity and the presence of a common‐ion salt ((n‐C4H9)4N+SO3CF−3) greatly increased the reactivity difference between the monomers. Thus the non‐dissociated species is more selective than the dissociated species. In contrast, the composition of pMeSt‐St copolymers produced by BF3O(C2H5)2 did not change with the solvent polarity. The difference in nature between the propagating species generated by CF3SO3H and by BF3O(C2H5)2 is discussed.