New micrometer-sized monodispersed self-assembled amphiphilic polystyrene/poly(n-butyl methacrylate) composite particles of hemispherical morphology: synthesis and characterization

Uniform micron-sized polystyrene template particles surface grafted with polyvinylpyrrolidone were prepared by dispersion polymerization of styrene in alcoholic solvents in the presence of polyvinylpyrrolidone as stabilizer. Poly(acrylic acid, sodium salt) derivatized polystyrene/ poly(n-butyl methacrylate) micron-sized composite particles of hemispherical morphology and narrow size distribution were formed by a single-step swelling of the uniform polystyrene template microspheres dispersed in water with emulsion droplets of the monomer n-butyl methacrylate containing the initiator benzoyl peroxide. n-Butyl methacrylate was then polymerized at 73 °C within the template microspheres in the presence of the water-soluble monomer acrylic acid, sodium salt. The sodium ions of the poly(acrylic acid) derivatized composite particles were then replaced with dodecylammonium ions by interacting these composite particles with excess dodecylamine hydrochloride. As a result of this process the surface of the hemispherical composite particles composed of hydrophilic polyvinylpyrrolidone chains on the polystyrene phase and hydrophobic dodecyl groups on the poly(acrylic acid) derivatized poly(n-butyl methacrylate) phase. These newly formed micron-sized composite particles show amphiphilic characteristics and aggregate to form micelle-like spherical clusters. The ability to control the template polystyrene microspheres' dimensions and various polymerization parameters may open a wide variety of self-assembled spherical and other structures composed of micron-sized particles for various fundamental and practical applications such as self-assembly processes and the formation of photonic bandgap crystals.