Miniemulsions of Vinyl Stearate. II. Light-Scattering Studies During the Polymerization

Abstract

The course of the polymerization of vinyl stearate has been followed by dilatometry and by light scattering. Kinetically stable and visually clear or at most opalescent 'miniemulsions' were used to minimize the scattering (otherwise large) by emulsion droplets. Light-scattering results demonstrate that the final particle size of the latexes may be greater or less than that of the emulsion droplets in the starting miniemulsion. This suggests that polymer particles are nucleated from the aqueous (micelle-containing) phase, and grow by transport of vinyl stearate monomer through the aqueous medium from the emulsion droplets to feed polymerization in the particles. Thus the droplets gradually decrease in size and disappear when all the monomer has been taken up by absorption into micelles or into growing particles. A previously proposed droplet-particle collision theory does not appear to be necessary.