Measurements of the rate of radical desorption from polymer latices during emulsion polymerisation

Abstract

Styrene and methylmethacrylate have been polymerised in emulsion. By using seed latices under controlled conditions it was possible to investigate the kinetics of radical desorption from the polymer particles. This required the average number of radicals per particle, n, to be less than 0.5. Values of the radical desorption coefficient, k₀, were not affected greatly by the monomer concentration in the particles or the degree of surface saturationby the surfactant (sodium dodecylsulphate). When cetylpyridinium chloride was used as a surfactant, the value of k₀ for methylmethacrylate polymerisation was decreased but the value for styrene was unchanged. By using different temperatures it was shown that k₀ conformed to an Arrhenius expression. The relevant values of the pre-exponential factors and activation energies were calculated for both monomers.