Influence of the polyether chain on the dissociation of “living” polymers obtained in the anionic polymerization of ethylene oxide

Conductivity studies were carried out on block copolymers of composition K⁺, ?(EO)_n- αMeSt-(St)_x -αMeSt-(EO)_n^?, K⁺, where n = 1–5 or 20, in THF. The conductivity of the solutions exhibits a strong tendency to increase as n is raised up to 3, and to change only slightly on further extension of the polyether chain. An equilibrium between ion pairs and free ions is established in the solution only when n is 1 or 2; for n ? 3, ion triplets are formed also. The dissociation constants for the ion pairs and the ion triplets and their temperature dependence were determined. The formation of ion triplets, as well as the changes in dissociation of the ion species on extending the polyether block, are explained by solvation of the counter-ion by the polyether chain.