Poly(styrene–isoprene–butadiene-g-SAN) graft copolymers: Size-controllable synthesis and their toughening properties

The poly(styrene–isoprene–butadiene) (PSIB) latexes with large particle diameters were synthesized in a seed-emulsion polymerization or followed by agglomerating with amphiphilic block copolymers, and their granularity uniformities were also investigated through the determination of PSIB grain-size distribution. Resultant PSIB latexes were functionalized with styrene–acrylonitrile random copolymers (SAN) which the chemical graft modification had been investigated as well. The large particle diameter of PSIB latex via a seed-emulsion polymerization showed a continuous and normal distribution, which was improved greatly with the dosages of emulsifier and seed-emulsion concentration. A bimodal PSIB latex with large-sized particles were also prepared by the agglomerating process with a hydrophilic polymer of poly(butylacrylate-methacrylic) acid after the radical emulsion polymerization and was greatly affected with addition of poly(butylacrylate-methacrylic) acid. Moreover, the higher value of graft yield of SAN copolymer onto PSIB latex was observed as compared to the PB latex and the following factors controlled the grafting degree of the particles: (i) the composition of monomers; (ii) the initiatorʹs content; (iii) the conditions for grafting copolymerization. Poly(styrene–isoprene–butadiene-g-SAN) graft copolymers (PSIB-g-SAN) were blended with SAN resins and their toughening properties were tested respectively. The effects of the composite polymer particles and the properties of PSIB-g-SAN particles were also discussed.