Successful miniemulsion polymerizations of very hydrophobic monomers, such as lauryl methacrylate and 4-tertbutyl styrene, initiated by very hydrophobic (i.e., completely water-insoluble) lauroyl peroxide, are reported. Conversion-time histories, as well as final latex properties, for example, the particle size distribution, are different from similar miniemulsion polymerizations in the presence of water-soluble initiators. The observed differences can be attributed to the average number of radicals inside a miniemulsion particle; the system obeys Smith-Ewart case I rather than Case II kinetics. Albeit the pairwise generation of radicals in the monomer droplets, substantial polymerization rates are observed. Water, present in the droplet interfacial layer, is supposed to act as chain transfer agent. The product of a chain transfer event is a hydroxyl radical, exit of this hydroxyl radical allows for the presence of single radicals in particles. The proposed mechanisms allow for agreement between initial droplet and final particle size distributions in miniemulsion polymerization initiated by lauroyl peroxide.

Miniemulsions, consisting of submicron droplets of very hydrophobic lauryl methacrylate or 4-tert-butyl styrene, are successfully polymerized using water-soluble sodium persulfate. Monitoring the calorimetric profile as well as the droplet and particle size distribution with conversion manifests a process of monomer redistribution, droplet disappearance, and narrowing of the particle size distribution. The observed reaction characteristics could be modeled adequately, using thermodynamic principles. The results of the work presented do not only have predicting value, but also enfeeble the idea of a one-to-one translation of monomer droplets into polymer particles in miniemulsion polymerization.