Anionic polymerization of styrene in 2-methyltetrahydrofuran

Abstract

“Living” anionic polymerizations of lithium, sodium, potassium, and caesium salts of polystyrylanions were investigated in 2-methyltetrahydrofuran at 25°C in the presence and absence of an electric field. The field increased the k″_pK″_½ term; k″_p is the free ion rate constant and K the dissociation constant of ion pairs. The K values of all four salts were determined from conductivity data, and the free ion rate constant was 7 × 10⁴ M^–1 s^–1. From the conductivity data, the field effect was concluded to be primarily due to an increase in k″_p with increase of the field strength. The k″_p reached a limiting value of ≈ 1.2 × 10⁵ M^–1 s^–1 above 3 kV/cm, which was virtually the same as those found in tetrahydropyran and in binary mixtures of benzene and tetrahydrofuran. The increase in k″_p was attributed to desolvation of solvent molecules weakly bound to free carbanion. The ion pair rate constants k′_p were 25, 23, 17 and 23 M^–1 s^–1 for Li⁺, Na⁺, K⁺ and Cs⁺ salts, respectively, and were not affected by the electric field.