Synthesis of Polymeric Nanoparticles by Reversible Addition-fragmentation Chain Transfer (raft) Polymerization in Co2-induced Miniemulsion

Implementation of controlled/living radical polymerization in miniemulsion (typically with oil droplet diameter of 20-500 nm) for synthesis of well-defined, polymeric nanoparticles is of particular interest as miniemulsions possess the inherent advantage that ideally each monomer droplet is transformed into a polymer particles(Zetterlund et al., 2008). However, the high energy requirement for miniemulsion preparation by traditional methods (such as ultrasonification) has precluded widespread industrial application. As such, some low energy emulsification techniques have been developed to generate miniemulsions for the preparation of polymeric nanoparticles.(Cheng et al., 2010, Zhang et al., 2008, Spernath and Magdassi, 2007, Sadtler et al., 2010, Spernath et al., 2009) Nevertheless, to the best of our knowledge, controlled/living radical polymerization has rarely been carried out in miniemulsion based on low energy emulsification, the only example being our work about nitroxide-mediated radical polymerization in miniemulsion on the basis of in situ surfactant formation without use of homogenization device(Guo et al., 2010). In this presentation, we introduce for the first time a novel method (Zhang et al., 2008) for synthesis of nanoparticles comprising well-defined polymer by the reversible generation of styrene-in-water miniemulsions with the anionic emulsifier disulfonated alkyl diphenyloxide sodium salt(Dowfax 8390) by use of compressed carbon dioxide in tandem with RAFT chemistry.