Novel graft copolymers from mechanistically-designed seeded emulsion polymerization

摘要

While natural rubber and natural rubber latex (NRL) have technical and environmental advantages, there are limitations in applications, which could be extended by creating a graft copolymer in the latex with artificial monomer(s) through the double bond on the cis-polyisoprene. Previous attempts to create such grafting through second-stage polymerization with the NRL as seed did not give uniform morphology of the resulting polymer, presumably because of insufficient grafting. This is overcome by combining two strategies: (a) the second-stage monomer system includes one or more components that are extremely water-insoluble, thereby avoiding secondary particle formation and subsequent imbibement, and (b) the second-stage monomer is chosen to have free-radical chemistry that can readily form graft sites with polyisoprene which undergo further propagation. One monomer that satisfies these criteria is lauryl acrylate, and indeed uniform morphology is observed in using this monomer polymerized with NRL as seed under appropriate conditions.