Living radical polymerization catalysts: Synthesis, application, and utilization of polymer products in the synthesis of metal nanoparticles

Living radical polymerization techniques are powerful tools for prepared specialty polymer products used in applications from biotechnology to electronics. Development of catalysts for the different methods is important for increased versatility. The goals of this research were to develop new radical addition-fragmentation chain transfer (RAFT) and cobalt mediated radical polymerization (CMRP) catalysts and utilize polymers produced through controlled radical polymerization techniques for the synthesis of metal nanoparticles. Vanadium complexes were designed to mimic conventional RAFT chain transfer agents and tested in the polymerization of methylacrylate (MA) and styrene. These complexes proved unsuitable for use as RAFT catalysts. Several cobalt complexes, using salen and salen derivative ligands, were prepared and tested as CMRP catalysts for the polymerization of MA and vinyl acetate (VAc). (R,R)-N,N\u27-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamino Cobalt (II) proved to be the most promising candidate for both polymers. MA was prepared with PDIs 1.32 and under while the VAc PDIs were under 1.50. In both cases, observations suggesting a controlled polymerization were reported. PDMAEMA synthesized using a RAFT polymerization was used to stabilize and control the formation of platinum, gold, and palladium nanoparticles. Protonation of the polymer chains using succinic acid or acidic metal complexes allowed for ionic cross-linking by the metal anions, which is observed through DLS analysis. Reduction of the metal complexes was then performed within the nanogel and the rapid stabilization by the polymer results in small well defined particles. Well defined particles were produced for each metal with different size ranges for each. Nanogel formation is critical mechanism for control in each system and was seen only in systems containing dianionic species