The methyl methacrylate(MMA) reversible addition-fragmentation chain transfer(RAFT) miniemulsion polymerization in the presence of β-cyclodextrin(β-CD) was investigated. β-CD is found to act both as an efficient so...The methyl methacrylate(MMA) reversible addition-fragmentation chain transfer(RAFT) miniemulsion polymerization in the presence of β-cyclodextrin(β-CD) was investigated. β-CD is found to act both as an efficient solubilizer for RAFT agent(2-cyanopro-2-yl dithiobenzoate) and as a stabilizer for heterogeneous polymerization. The RAFT miniemulsion polymerizations with or without β-CD were compared in terms of kinetics and the molecular weight distribution. The problem of poor latex stability was observed in this system. A good result of the control over RAFT miniemulsion polymerization of MMA was obtained with β-CD. The increase of the molecular weight of poly(methyl methacrylate) shows a linear relationship with the monomer conversion. The polydispersity index of the polymer with β-CD(PDI=1.18—1.21) is smaller than that without β-CD. TEM photographs showed that the PMMA particles produced with β-CD had smooth surfaces and uniform particle size. Higher amount of sodium dodecyl sulfate and hexadecane was found in favor of improving the controllability of the system. Oil soluble initiator is beneficial to the controllability of the polymerization.展开更多
Two opposing explanations to significant rate retardation in dithioester-mediated polymerization with reversible addition fragmentation chain transfer process(RAFT),e.g: slow fragmentation of intermediate radicals (Mo...Two opposing explanations to significant rate retardation in dithioester-mediated polymerization with reversible addition fragmentation chain transfer process(RAFT),e.g: slow fragmentation of intermediate radicals (Model A),and cross termination between intermediates and growing radicals (Model B),had been proposed by Davis and Monteiro independently. In this paper,a comparison of simulation results of Model A and Model B with experiment results was presented. The simulated results show that the intermediate concentration of Model A is much higher than that of experiments,while Model B gives a rather high polymerization rate than experiments with large concentration of dithioesters. The reaction model was better fitted,in light of kinetics,intermediate concentration and distribution of molecular weight,to experimental data when both cross termination and slow fragmentation were taken into account. [WT5HZ]展开更多
文摘The methyl methacrylate(MMA) reversible addition-fragmentation chain transfer(RAFT) miniemulsion polymerization in the presence of β-cyclodextrin(β-CD) was investigated. β-CD is found to act both as an efficient solubilizer for RAFT agent(2-cyanopro-2-yl dithiobenzoate) and as a stabilizer for heterogeneous polymerization. The RAFT miniemulsion polymerizations with or without β-CD were compared in terms of kinetics and the molecular weight distribution. The problem of poor latex stability was observed in this system. A good result of the control over RAFT miniemulsion polymerization of MMA was obtained with β-CD. The increase of the molecular weight of poly(methyl methacrylate) shows a linear relationship with the monomer conversion. The polydispersity index of the polymer with β-CD(PDI=1.18—1.21) is smaller than that without β-CD. TEM photographs showed that the PMMA particles produced with β-CD had smooth surfaces and uniform particle size. Higher amount of sodium dodecyl sulfate and hexadecane was found in favor of improving the controllability of the system. Oil soluble initiator is beneficial to the controllability of the polymerization.
文摘Two opposing explanations to significant rate retardation in dithioester-mediated polymerization with reversible addition fragmentation chain transfer process(RAFT),e.g: slow fragmentation of intermediate radicals (Model A),and cross termination between intermediates and growing radicals (Model B),had been proposed by Davis and Monteiro independently. In this paper,a comparison of simulation results of Model A and Model B with experiment results was presented. The simulated results show that the intermediate concentration of Model A is much higher than that of experiments,while Model B gives a rather high polymerization rate than experiments with large concentration of dithioesters. The reaction model was better fitted,in light of kinetics,intermediate concentration and distribution of molecular weight,to experimental data when both cross termination and slow fragmentation were taken into account. [WT5HZ]
