Synthesis of poly(styrene-co-methyl methacrylate) nanospheres by ultrasound-mediated Pickering nanoemulsion polymerization

Poly (styrene-co-methyl methacrylate) (PS-co-PMMA) nanospheres were synthesized by ultrasound-mediated Pickering nanoemulsion polymerization using halloysite nanotubes (HNTs) as a stabilizer. A relatively high conversion (approximate to 99%) was obtained in a short span of time (60 min) relative to (approximate to 97%) for that obtained by conventional emulsion polymerization performed without ultrasound. The initial rate of polymerization and the conversion were found to be increasing with the acoustic intensity in the range of 12.5-25 W/cm(2)). The synthesized copolymer nanosphere particles exhibited a perfect spherical shape (from TEM analysis), good stability (from zeta-potential analysis), high molecular weight (M-w approximate to 311 kDa from Gel permeation chromatography), and excellent thermal properties (T-g approximate to 120 degrees C from DSC and TGA) as a result of the combined physicochemical effects of acoustic cavitation. The formation of nanosized emulsion droplets stabilized by HNTs ultimately yielded nanospheres of PS-co-PMMA with an average size of approximately equal to 82.8 nm. The PS-co-PMMA nanospheres can have potential applications in medicine, dentistry, paper, paint, and automotive industries.