Kinetic studies and applications of atom transfer radical polymerization.

摘要

The study of basic kinetic parameters in atom transfer radial polymerization (ATRP) is reported. Novel methods were developed for measuring the activation and deactivation rate constants in ATRP. Using the developed methods, the rate constants for several model systems were determined under various conditions. The obtained data were consistent with the observations in ATRP, and provided further quantitative insight into understanding of the ATRP processes. Two applications of the developed methods are described. Firstly, the participation of free radical intermediates in copper catalyzed atom transfer reactions was investigated using three kinetic methods: racemization, halogen exchange and trapping reactions. The similar rates of these three reactions suggested that the rate-determining step in these three reactions is the generation of the same intermediate, presumably a free radical in the atom transfer process. The second application of the developed methods was comparison of the catalytic activity of several Cu-based tridentate ligands. The systematic evaluation of activities of different ligands elucidated a correlation between atom transfer reactions and ligand structures.; The controlled homopolymerizations of methyl acrylate and acrylonitrile are reported. The use of CuBr/substituted 2,2′-bipyridine based catalysts led to the successful controlled ATRP of methyl acrylate. The results of the kinetic study of methyl acrylate were consistent with the proposed mechanism. Also, the successful preparation of well-defined polyacrylonitrile was achieved. However, there were questions about the side reactions resulting in the reduction in the polymerization rate. An interpretation of the abnonnal kinetic behavior was proposed based on extensive end group analysis.; Using site transformation techniques, block copolymerizations of two monomers were achieved where one monomer was polymerizable via ATRP and the other monomer was not. Three different examples are presented. The first study was the ring opening metathesis polymerization (ROMP) of strained monomers such as norbornene and dicyclopentadiene using a molybdenum based alkylidine initiator, followed by ATRP. Second, four different methods of block copolymerization, combining atom transfer radical polymerization (ATRP) and conventional radical polymerization of vinyl acetate, were studied. Also, a method to modify poly(vinyl chloride) with ATRP was developed. The modification of vinyl chloride was achieved by grafting from PVC backbone containing ATRP initiators.; Immobilizing ATRP catalysts on solid supports was developed using either inorganic or organic supports. Through the initial studies, the difficulties related to the diffusion controlled deactivation reaction, were found.