| The kinetics of Atom Transfer Radical Polymerization (ATRP) is discussed along with applications to materials synthesis. Specifically, a full kinetic investigation of the ATRP of methyl acrylate using methyl 2-bromopropionate as the initiator and the Cu(I)Br/4,4′-di-(5-nonyl)-2,2 ′-bipyridine catalyst system is detailed, along with unique features of the system. Evidence for a reversible interaction between the methyl acrylate radicals generated in the conventional radical polymerization initiated by AIBN and the CuBr/N,N,N′, N″,N″-pentamethyldiethylenctriamine complex is presented, along with a detailed explanation of its relevance to ATRP. The optimal conditions for the ATRP of t-butyl acrylate using the Cu(I)Br/NNN,N″,N ′-pentamethyldiethylenetriamine catalyst system are also detailed. The poly(t-butyl acrylate) was subsequently hydrolyzed to poly(acrylic acid), which provided a route to amphiphilic, block copolymers when combined with poly(styrene). Several chain architectures and topologies were prepared and their efficiency as surfactants in the conventional emulsion polymerization of styrene was investigated. These details are presented in a corresponding publication. The ATRP of n-butylmethacrylate was also undertaken, again using the Cu(I)/N,N,N′ ,N″,N ″-pentamethyldiethylenetriamine catalyst system. However, the high equilibrium constant for the monomer combined with the high activity of the catalyst created a system with a high concentration of radicals that was difficult to control. Approaches to overcoming these problems are presented. Additionally, different combinations of alkyl (pseudo)halide initiators and Cu(I) species were used for the ATRP of styrene and methyl acrylate to explore their effects of the polymerizations. The thiocyanate based initiator and Cu(I) complex, although useful when combined with a halogen containing species, cannot be used together, as an uncontrolled polymerization results. Reasons behind these results are discussed. Furthermore, it was expected that an iodine-based system would promote the most rapid ATRP reaction due to the lability of the carbon-iodine bond, however, this was not the case. Possible explanations are presented. Finally, using the knowledge gained in the investigations of the homopolymerizations, mono-, di-, and trifuntional ABC triblock copolymers were successfully synthesized that combined several different types of monomers including styrene, acrylates, methacrylates, and vinyl pyridine. Strategies to create well-defined block copolymers via ATRP are detailed, with an emphasis placed on achieving control over the polymerization through manipulation of the reaction conditions. |
