Polymerization of α-methylstyrene by living polymer in tetrahydrofuran

Kinetics of polymerization of α-methylstyrene by poly-α-methylstyrylsodium (a “living” polymer) has been studied in tetrahydrofuran at ?78°C. Complex dependences were established: that of the conversion X on reduced time φ and that of the apparent rate constant for the polymer chain propagation on conversion X and on the concentration of living polymers and monomer. The experimental data obtained were explained by assuming a coordination mechanism of anionic polymerization including the following elementary reaction: (a) generation of active polymerization centers (K₁) by interaction of the living polymer with the monomer; (b) propagation of the polymer chains (K₂); (c) monomolecular (K₃₁) and bimolecular (K₃₂) reactions of isomerization of active centers resulting in the formation of high molecular weight living polymers capable of again becoming active centers of polymerization. Approximate derivation of kinetic equation was carried out and the constants of elementary reactions were determined (K₁ = 0.15, K₂ = 24, K₃₂ = 14.1./mole-min and K₃₁ = 0.05 min^?1). The coincidence of the expected dependencies X = F(τ; φ) K_p = F(X; n₀^?1/2); dx/dτ = F(n₀) with the experimental ones was followed with the aid of computers. The expected change in the values of X and K_p depending on the contribution of each elementary reaction to the overall polymerization process was analyzed.