Polyelectrolytes. IV. Conductance of n‐butyl bromide addition compounds of 4‐vinylpyridine‐styrene copolymers in nitromethane‐dioxane mixtures

Abstract

Abstract The conductance of a series of salts made by the addition of n‐butyl bromide to 4‐vinylpyridine‐styrene copolymers (1.5 to 90 mole per cent vinylpyridine) has been measured in dioxane (ϵ′ = 2.2), ethylene dichloride (ϵ′ = 10.2), and a series of nitromethane‐dioxane mixtures (16.0 ≤ ϵ′ ≤ 39.4). Three independent arguments deduced from the data show that ionic association under the influence of interionic electrostatic forces must occur in solutions of polyelectrolytes in such a way that a certain average fraction of the counter ions accompany the large polycation and contribute nothing to conductance. First, the conductance at fixed copolymer composition and fixed salt concentration decreases with decreasing dielectric constant of the solvent medium. Second, at a given counter ion concentration in a given solvent, the conductance decreases with increasing pyridonium content of the chain. Third, for a given salt and solvent, the conductance decreases with increasing salt concentration at a rate much slower than that characteristic of simple electrolytes.