Anionic copolymerization of 1,1-diphenylethylene and 2,3-dimethylbutadiene

1,1-Diphenylethylene (M₂) and 2,3-dimethylbutadiene (M₁) were copolymerized with n-butyllithium in tetrahydrofuran. The rate of consumption of each monomer was followed by the change of high resolution NMR spectra of the reaction mixture. The copolymerization proceeded alternately, if the ratio of initial monomer concentrations, M₂]₀/M₁]₀, was sufficiently larger than unity. By assuming the rate constant k₂₂ to be zero, the constants k₂₁ were obtained from the consumption rates of the monomers. In the alternating copolymerization, 2,3-dimethylbutadiene was incorporated into the copolymer only as the 1,4-structure, while the 1,2-structure was predominant in homopolymerization.