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.