Polyvinyl Alcohol (PVA) As Protective Colloid for Polystyrene Nanoparticles Synthesis Initiated By Oil-Soluble Initiator

Compared with low molecular surfactants, polyvinyl alcohol (PVA) could afford latexes with particular tackiness as an important property for various applications. However, until now, except for some highly reactive monomers, most of monomers including styrene seldom use PVA as protective colloid in emulsion polymerization due to the lack of its stability. In this work, we used oil-soluble initiator, 2,2¡¯-azobisisobutyronitrile (AIBN), to accelerate the emulsion copolymerization of styrene and divinyl benzene in PVA colloids and synthesize polystyrene (PS) nanoparticles within 50 min at 70 ^oC successfully. Even at the monomer-to-water ratio as high as 4:1, the emulsion system could keep stable throughout the emulsion polymerization with only PVA as stabilizer, and the polymerization in PVA colloids was always dominant. The adjustment of the size of the PS nanoparticles in the range from 70 nm to 100 nm was achieved simply by changing the polymerization temperature, the addition of PVA, or the monomer-to-water ratio. The PVA adhering on the surface of the PS nanoparticles showed stable modification effect in the aqueous latexes, and also could be washed completely by dimethylsulfoxide (DMSO) to obtain PS nanoparticles without surfactant contaminant. This method was also exploited to synthesize poly(styrene-co-methyl methacrylate) and poly(styrene-co-4-chlorostyrene) nanoparticles, possessing good potentials in functional polymeric nanoparticles production with the advantages of high capacity and broad applicability.