A kinetic model was developed to describe the atom transfer radical polymerization (ATRP) of 2(N,N-dimethylarnino) ethyl methacrylate (DMAEMA). The model was based on a polymerization mechanism, which included the ato...A kinetic model was developed to describe the atom transfer radical polymerization (ATRP) of 2(N,N-dimethylarnino) ethyl methacrylate (DMAEMA). The model was based on a polymerization mechanism, which included the atom transfer equilibrium for primary radical, the propagation of growing polymer radical, and the atom transfer equilibrium for the growing polymer radical. An experiment was carried out to measure the conversion of monomer, the number-average molecular weight of polymer and molecular weight distribution for the ATRP process of DMAEMA. The experimental data were used to correlate the kinetic model and rate constants were obtained. The rate constants of activation and deactivation in the atom transfer equilibrium for primary radical are 1.0 x 10(4) L(.)mol(-1.)s(-1) and 0.04 L(.)mol(-1.)s(-1), respectively. The rate constant of the propagation of growing polymer radical is 8.50 L(.)mol(-1.)s(-1), and the rate constants of activation and deactivation in the atom transfer equilibrium for growing polymer radical are 0.045 L(.)mol(-1.)s(-1) and 1.2 x 10(5) L(.)mol(-1.)s(-1), respectively. The values of the rate constants represent the features of the ATRP process. The kinetic model was used to calculate the ATRP process of DMAEMA. The results show that the calculations agree well with the measurements.展开更多
Since tertiary amines （Cα-H） can be oxidized by peroxides and transition metal cations in high oxidation states into Ca2＋ radicals to initiate vinylic polymerizations of methacrylates, Cu2＋ and 2-（N,N-dimethylam...Since tertiary amines （Cα-H） can be oxidized by peroxides and transition metal cations in high oxidation states into Ca2＋ radicals to initiate vinylic polymerizations of methacrylates, Cu2＋ and 2-（N,N-dimethylamino）ethyl methacrylate （DMAEMA） form a polymerizable redox initiating pair, in which DMAEMA serves as an intrinsically reducing inimer. CuSOa-catalyzed aqueous self-initiated radical polymerizations of DMAEMA were successfully performed at ambient temperature via a continuous Cu2＋-tertiary amine redox initiation based on catalyst regeneration in the presence of O2. The polymerization kinetics was monitored by gas chromatography and the structure of PDMAEMA was characterized by gel- permeation chromatography, nuclear magnetic resonance spectroscopy, laser light scattering and online intrinsic-viscosity analysis. Both the monomer conversion and the molecular weight of PDMAEMA increase with the reaction while the molecular weight distribution maintains rather broad, as the Cu2＋-DMAEMA redox-initiation leads to linear PDMAEMA chains with terminal methacryloxyl moieties, and the Cu2＋-PDMAEMA redox-initiation results in branched chains. The branched topology forms and develops only for the high-MW components of the PDMAEMA. Our results provide a facile strategy to prepare branched polymers from such commercially available intrinsically reducing inimers using a negligible concentration of regenerative air-stable catalysts.展开更多
文摘A kinetic model was developed to describe the atom transfer radical polymerization (ATRP) of 2(N,N-dimethylarnino) ethyl methacrylate (DMAEMA). The model was based on a polymerization mechanism, which included the atom transfer equilibrium for primary radical, the propagation of growing polymer radical, and the atom transfer equilibrium for the growing polymer radical. An experiment was carried out to measure the conversion of monomer, the number-average molecular weight of polymer and molecular weight distribution for the ATRP process of DMAEMA. The experimental data were used to correlate the kinetic model and rate constants were obtained. The rate constants of activation and deactivation in the atom transfer equilibrium for primary radical are 1.0 x 10(4) L(.)mol(-1.)s(-1) and 0.04 L(.)mol(-1.)s(-1), respectively. The rate constant of the propagation of growing polymer radical is 8.50 L(.)mol(-1.)s(-1), and the rate constants of activation and deactivation in the atom transfer equilibrium for growing polymer radical are 0.045 L(.)mol(-1.)s(-1) and 1.2 x 10(5) L(.)mol(-1.)s(-1), respectively. The values of the rate constants represent the features of the ATRP process. The kinetic model was used to calculate the ATRP process of DMAEMA. The results show that the calculations agree well with the measurements.
基金financially supported by the National Natural Science Foundation of China(No.20674033)Natural Science Foundation of Jiangsu Province(No.BK2008142)Scientific Research Foundation for the Returned Overseas Chinese Scholars(State Education Ministry)
文摘Since tertiary amines （Cα-H） can be oxidized by peroxides and transition metal cations in high oxidation states into Ca2＋ radicals to initiate vinylic polymerizations of methacrylates, Cu2＋ and 2-（N,N-dimethylamino）ethyl methacrylate （DMAEMA） form a polymerizable redox initiating pair, in which DMAEMA serves as an intrinsically reducing inimer. CuSOa-catalyzed aqueous self-initiated radical polymerizations of DMAEMA were successfully performed at ambient temperature via a continuous Cu2＋-tertiary amine redox initiation based on catalyst regeneration in the presence of O2. The polymerization kinetics was monitored by gas chromatography and the structure of PDMAEMA was characterized by gel- permeation chromatography, nuclear magnetic resonance spectroscopy, laser light scattering and online intrinsic-viscosity analysis. Both the monomer conversion and the molecular weight of PDMAEMA increase with the reaction while the molecular weight distribution maintains rather broad, as the Cu2＋-DMAEMA redox-initiation leads to linear PDMAEMA chains with terminal methacryloxyl moieties, and the Cu2＋-PDMAEMA redox-initiation results in branched chains. The branched topology forms and develops only for the high-MW components of the PDMAEMA. Our results provide a facile strategy to prepare branched polymers from such commercially available intrinsically reducing inimers using a negligible concentration of regenerative air-stable catalysts.
