The copolymerization of styrene and sulphur dioxide - I. Properties and composition of the copolymer, and evidence for the existence of a styrene/sulphur dioxide complex

Abstract

Copolymers of styrene and sulphur dioxide have been prepared over a wide range of conditions. The minimum styrene to sulphur dioxide ratio in polymers prepared by free radical polymerization has been found to be 2: 1; this is interpreted in terms of copolymerization of styrene and a 1: 1 styrene/sulphur dioxide molecular complex, in which the complex-to-complex propagation reaction does not occur to a significant extent. Measurements of ultra-violet absorption have confirmed the existence of a 1: 1 complex. The dependence of polymer composition on the styrene and sulphur dioxide concentration are shown to be in agreement with the reaction scheme, though at low styrene concentrations the effect of depropagation reactions must be taken into account. The variation of polymer composition with temperature has been measured and indicates practically zero activation energy for the addition of the complex to a styryl radical. In the absence of catalyst at very high sulphur dioxide concentrations, the free radical polysulphone formation proceeds simultaneously with a spontaneous ionic polymerization producing polystyrene. A cosolvency effect of mixtures of polar and non-polar solvents on styrene polysulphone is described and discussed.