Kinetics of anionic polymerization of styrene in binary mixtures of dimethoxyethane and benzene

Abstract

The kinetics of anionic polymerization of polystyryl salts with various gegen ions have been investigated spectrophotometrically in 1,2-dimethoxyethane (DME)+ benzene mixtures at 25°C. The behaviour of two types of polymers, viz. one- and two-ended polymers, was studied for sodium and caesium salts. The two-ended sodium salt is as reactive as the one-ended salt, whereas the two-ended caesium salt is less reactive than the one-ended salt. The conductance of the two-ended sodium salt is smaller than that of the one-ended, whereas the conductance of the two-ended caesium salt is larger than that of the one-ended salt. The ion-pair rate constants k′_p in the DME + benzene (50 : 50) mixture are 360, 182 and 90 dm³ mol^–1 s^–1 for the sodium, potassium and caesium salts. The dissociation constants K are 4.7 × 10^–10, 1.3 × 10^–10 and 3.5 × 10^–12 mol dm^–3 for the sodium, potassium and caesium salts. The free ion rate constant k″_p is 9–10 × 10⁴ dm³ mol^–1 s^–1 for these salts. The contribution of the intra-molecular triple-ion was observed for the two-ended living polystyrene and the rate constant k″′_p(c) of this ionic species is ∼1000 dm³ mol^–1 s^–1, practically independent of solvent, and is smaller than the rate constant of the solvent-separated intermolecular triple ion (kt′_p∼1.2 × 10⁵ dm³ mol^–1 s^–1).