ABSTRACT
The signicant differences of miniemulsion polymerization to emulsion polymerization are the much smaller droplet size obtained by using high shear force during miniemulsion preparation and the use of costabilizer to suppress the Ostwald ripening. The monomer droplet size for miniemulsion polymerization is typically around 50-300 nm, much smaller than that of the monomer droplets in emulsion polymerization. Hence, the droplet surface area in miniemulsion systems is very large compared to emulsion. The surfactant concentration in the formulation is so controlled that little free surfactant is present in the form of micelles as most of the surfactant is adsorbed at the droplet surface. Because of the large surface area in miniemulsion polymerization systems, particle nucleation is primarily via radical entry into monomer droplets, which are the polymerization loci in miniemulsion polymerization. There is no monomer transfer between the droplets, and each droplet acts like a nanoreactor itself and stays almost unchanged during polymerization. This allows the use of very hydrophobic monomers in the miniemulsion polymerization, which is not accessible to the conventional emulsion polymerization.
