| Abstract: | The evolution of monomer droplets and latex particles of methyl methacrylate miniemulsions, initiated by an oil‐phase initiator, stabilized by a cationic surfactant mixture, and costabilized by different amounts of hexadecane, was investigated. With an increasing hexadecane concentration, the ultrasonication time required for the miniemulsions to reach a critically stabilized state was reduced, and a unimodal size distribution of the droplets with a decreasing average diameter was obtained. For lower hexadecane concentrations, a bimodal size distribution of the latex particles, with a significant increase in the volume fraction of the smaller latex particles, was achieved after the polymerization. The enhanced growth of the volume fraction of the smaller latex particles came from both nucleation of the shrinking droplets due to Ostwald ripening and homogeneous and/or micellar nucleation, if micelles existed, triggered by radicals in the aqueous phase. For high hexadecane concentrations, Ostwald ripening was effectively retarded, and the miniemulsions were sufficiently stabilized against the degradation of molecular diffusion. The size distributions of the droplets and latex particles were almost identical. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4603–4610, 2006 |
