Synthesis and characterization of surfmers for latex stabilization in RAFT-mediated miniemulsion polymerization

[摘要] Synthesis of two surfmers (cationic and anionic) was carried out and the surfmers were usedto stabilize particles in miniemulsion polymerization. Surfmers were used to eliminateadverse effects associated with free surfactant in the final product e.g. films and coatings. TheReversible Addition Fragmentation chain Transfer (RAFT) polymerization process was usedin miniemulsion polymerization reactions to control the molecular weight distribution. RAFToffers a number of advantages that include its compatibility with a wide range of monomersand solvents. Moreover block copolymer synthesis is possible via chain extension.A comparative study between classical surfactants and surfmers was conducted in regard toreaction rates and molar mass distribution. The rates of reactions of surfmer stabilized RAFTminiemulsion polymerization of Styrene and MMA were similar (in most cases) to classicalsurfactant stabilized RAFT miniemulsion polymerization reactions. The final particle sizeswere also similar for polystyrene latexes stabilized by surfmers and classical surfactants.However PMMA latexes stabilized by surfmers had larger particle sizes compared to latexesstabilized by classical surfactants.The surfmers were also oligomerized in homogeneous media using the RAFT process andtheir Mn values were estimated using UV-VIS spectroscopy. The oligosurfmers were thenused as emulsifiers in RAFT miniemulsion polymerization. The rates of reaction were slowerthan rates obtain when the surfmers (monomer or oligosurfmers) were used directly asemulsifiers in RAFT miniemulsion polymerization of styrene and MMA. The final latexparticle sizes obtained with oligosurfmers were also larger than that of latex stabilized by theirparent monomers.The RAFT process was successfully applied in miniemulsion polymerization in both classicalsurfactant and surfmer stabilized miniemulsions. The molecular weight increased withconversion showing that the molecular weights of the polymers were controlled.

[发布机构] Stellenbosch University