Miniemulsion copolymerization of methyl methacrylate and butyl acrylate in the presence of vinyl siloxane rubber

Vinyl siloxane rubber was successfully used as the co-stabilizer in the miniemulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA) initiated by ammonium persulfate. Effects of the molecular weight, vinyl content, and the amount of vinyl siloxane rubber on the kinetics and the particle morphology of the latex prepared were investigated. The rate of copolymerization was found to decrease with an increase in the molecular weight (100,000–275,000 g/mol) and the vinyl amount of the siloxane (0.1–2.0 wt.%). The highest rate of miniemulsion copolymerization was observed at the VSR amount of 1.0 g (10% based on the weight of monomers). TEM photos showed that all the siloxane was incorporated into the polyacrylate particle. This suggests that droplet nucleation mechanism was prominent in the process of the polymerization. Core-shell structure of the particle could be found in high amount of VSR recipe. 1H NMR, and FTIR analysis demonstrated that the vinyl did participate in the reaction during the polymerization and contribute to the grafting between vinyl siloxane rubber (VSR) and polyacrylate. Extraction tests showed that the degree of grafting of the VSR to polyacrylate was increased with an increase of the vinyl content in the VSR used.