SYNTHESIS OF STYRENE BUTADIENE COPOLYMER/SiO2 AND POLYBUTADIENE/SiO2 NANOPARTICLES VIA DIFFERENTIAL MICROEMULSION POLYMERIZATION

Abstract

Differential microemulsion polymerization (DMP) was selected for synthesis of styrene butadiene copolymer (SBR)-SiO2, polybutadiene (PB)-SiO2 and polystyrene (PS)-SiO2 nanoparticles. The core-shell structure was designed to achieve a monodispersion with reduced nanosilica aggregation. The effects of silica loading, monomer to water ratio, surfactant concentration and initiator concentration on monomer conversion, particle size, particle size distribution and grafting efficiency were investigated. SBR-SiO2 nanoparticles with a size range of 20-50 nm, high monomer conversion of 86.6% and high grafting efficiency of 75.5% were obtained at a low surfactant concentration of 3 wt% based on monomer. For PB-SiO2 synthesis via DMP, a high monomer conversion (81.5%), grafting efficiency (78.5%) and small particle size (27 nm) was obtained under optimum reaction conditions. In addition, PS-SiO2 nanoparticles with a small particle size of 33.5 nm and high polymer grafting efficiency of 76.3 was also obtained by DMP. Diimide reduction was applied to synthesize hydrogenated polybutadiene (HPB)-SiO2. A high hydrogenation degree of 98.6% was achieved at a ratio of hydrazine to hydrogen peroxide of 0.75:1. HPB-SiO2 showed a maximum degradation temperature of 469.6 °C resulting in excellent thermal stability. A new nanocomposite of SBR-SiO2, PB-SiO2, HPB-SiO2 and PS-SiO2 could be used as a novel nanofiller in natural rubber and styrene butadiene rubber latex. Especially, NR/HPB-SiO2 composites had improved mechanical and thermal properties, and exhibited good resistance toward ozone exposure.