Application of the theory of colloid stability to the problem of particle formation in aqueous solutions of vinyl acetate

Abstract

The problem of particle formation in aqueous solutions of vinyl acetate is treated according to the Deryaguin‐Landau‐Verwey‐Overbeek (D.L.V.O.) theory of the stability of lyophobic colloids.In the absence of surfactants, polymer particles are stabilised by ionic end‐groups derived from persulphate initiator. Palit's dye partition method is used to determine the number of these end‐groups and the amount of adsorbed sodium dodecyl sulphate which was used as emulsifying agent in some experiments; this enables the electrical forces of repulsion between particles to be calculated. The Hamaker constant which defines the magnitude of the van der Waals' forces of attraction between particles has been estimated for polyvinyl acetate. The dependence of the stability of the polymer dispersion formed on the concentrations of initiator, emulsifier, etc. is investigated; the observations accord with expectations on the basis of D.L.V.O. theory. It is shown that small particles are unstable with respect to coalescence with larger particles. The processes of polymerisation and particle growth are essentially independent in this system.