Cationic polymerization of p-substituted α-methylstyrenes, 2. Crystalline polymers from p-methyl- and p-isopropyl-α-methylstyrene

Under identical conditions of cationic polymerization at low temperature 2-(p-tolyl)-1-propene (α,p-dimethylstyrene) gave polymers with much higher syndiotactic contents than unsubstituted α-methylstyrene. All samples of poly(α,p-dimethylstyrene) were crystalline, but poly(α-methylstyrene) did not crystallize even at high degrees of stereoregularity. Similarly polymers of p-isopropyl-α-methylstyrene were crystalline, and the crystalline properties of copolymers of the three monomers were investigated and compared to those of the homopolymers. The rôles of stereoregularity and crystallizability in forming crystalline products were considered.