Functional Highly Branched Polymers Synthesized via a One-Pot Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization

摘要

Highly branched polymers provide an excellent alternative to the more synthetically challenging dendrimers. Although they have less perfect branching structures than the latter, highly branched polymers retain high degrees of functionality, have improved solubility and low viscosity and therefore provide a cheaper alternative to dendrimers for applications such as resin modification, encapsulation, polymeric liquid crystals, pharmaceutical use, catalysis and electroluminescent devices. The creation and development of highly branched macromolecules with well-defined architectures, via one-step processes is well documented in the literature, but mostly concern step-growth polymerization via polycondensation of ABx monomers -3 Frechet et al first reported the self- condensing vinyl polymerisation (SCVP) process, where a vinyl monomer presents a second functional group that is capable of initiating the polymerization of other vinyl groups. Such technique was applied to cationic polymerization, group transfer polymerization and living radical polymerizations However, this process is difficult to exploit industrially as it requires expensive, tailored vinyl monomers with specific functional groups that require complex syntheses and the polymerizations need to be stopped at low conversions. Sherrington and co- workers recently reported a facile, versatile and cost-effective routes to the synthesis of branched polymers. Their strategy involves the conventional free radical polymerization of a vinyl monomer, in the presence of a multifunctional vinyl comonomer ('brancher') and a conventional chain transfer agents that prevent crosslinking -11 We present here our latest results on the use of RAFT/MADIX agents as chain transfer agents for similar systems. The use of reversible addition fragmentation chain transfer (RAFT) polymerization and macromolecular architecture design by interchange of xanthates (MADIX) as polymerization systems not only permits the synthesis of highly branched polymers that are better defined, but also it gives access to more complex macromolecular architectures.