Cationic polymerization α,β‐disubstituted olefins. Part I. Cationic copolymerization of β‐methylstyrenes

Steric and electronic effects of the β‐methyl group on monomer reactivity have been studied by copolymerization of styrenes and β‐methylstyrenes. Steric hindrance of the β‐methyl group in the transition state of homopolymerization is so great that the rate of the propagation reaction is considered to be depressed by as much as 1/10−1/20 of the corresponding styrene derivatives. In contrast to this, steric hindrance of the β‐methyl group in cross propagation reactions with styrene is found to be very small. The monomer reactivity itself of β‐methylstyrenes is a little lower than that of corresponding styrenes. This lowered reactivity of β‐methylstyrenes is considered to be due to the electronic effect of the β‐methyl group.