The bulk polymerization of styrene catalyzed by Nd(P204)3/MgBu2/HMPA (hexamethyl phospho-ramide) was carried out in capped glass tubes. The effects of reaction conditions on polymerization conversion and molecular wei...The bulk polymerization of styrene catalyzed by Nd(P204)3/MgBu2/HMPA (hexamethyl phospho-ramide) was carried out in capped glass tubes. The effects of reaction conditions on polymerization conversion and molecular weight in the range of high conversion were investigated. The molecular weight of the resultant polymers is dramatically high and its distribution is relatively narrow. The polymerization process demonstrates the feature of living polymerization and auto-acceleration phenomenon. The auto-acceleration phenomenon is attributed to the non-instantaneous formation of the active species. The experimental data suggest that chain transfer to MgBu2 is one of the factors governing the molecular weight development. A mechanism of polymerization is presented with the chain transfer process incorporated.展开更多
The ＂living＇/controlled radical polymerization （LRP） of styrene （St） at room temperature is rarely reported. In this work, copper（0） （Cu（0））-mediated radical polymerization of St at room temperature was in...The ＂living＇/controlled radical polymerization （LRP） of styrene （St） at room temperature is rarely reported. In this work, copper（0） （Cu（0））-mediated radical polymerization of St at room temperature was investigated in detail. Dimethyl sulfoxide （DMSO）, N,N-dimethylformamide （DMF） as well as a binary solvent, tetrahydrofuravdl,l,l,3,3,3-hexafluoro-2- propanol were used as the solvents, respectively. Methyl-2-bromopropionate and ethyl 2-bromoisobutyrate were used as the initiators, respectively. The polymerization proceeded smoothly with moderate conversions at room temperature. It was found that DMF was a good solvent with the essential features of LRP, while DMSO was a poor solvent with uncontrollable molecular weights. Besides, the match among the initiator, solvent and molar ratios of reactants can modulate the livingness of the polymerization, and the proper selection of ligand was also crucial to a controlled process. This work provided a first example of Cu（0）-mediated radical polymerization of St at room temperature, which would enrich and strength the LRP technique.展开更多
A starved feed reactor (SFR) is a semi-batch polymerization reactor where initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. T...A starved feed reactor (SFR) is a semi-batch polymerization reactor where initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. The added initiator decomposes instantaneously and the added monomer polymerizes immediately. The molecular weight (MW) and molecular weight distribution (MWD) of the product polymer can be effectively controlled by the feed ratio of monomer to initiator. This paper presents a study on the MWD of styrene polymerization in a SFR. The MWD model parameters are regressed with experimental data. Although the solids fraction in the SFR is high (higher than 50%), viscosity is not too high and the 'gel effect' is weak due to the low molecular weight of the products. It is found that the termination rate constant is a power function of molecular weight, radicals terminate via 100% combination, the thermal initiation can be neglected even at high reaction temperature studied. And calculated results indicate that in the SFR, the validity of the long chain assumption becomes doubted. It appears that other alterative assumption should be found for an improved model.展开更多
The behaviour of water soluble and monomer soluble inhibitors in emulsion polymerization of monomersfollowing Case Ⅱ kinetics(e.g.styrene)has been investigated.Experimental studies reveal that inhibitors canhave an a...The behaviour of water soluble and monomer soluble inhibitors in emulsion polymerization of monomersfollowing Case Ⅱ kinetics(e.g.styrene)has been investigated.Experimental studies reveal that inhibitors canhave an appreciable effect on both polymer particle nucleation and growth.A mathematical model showingthese effects has been developed and simulation studies have been done.The simulation results imply that theconsequences of these effects of monomer soluble inhibitors for industrial emulsion polymerization may be quiteserious.展开更多
The difference between apparent grafting ratio and true grafting ratio in bulk graft copolymerization of styrene onto rubber and the change of rubber particle size during the overall polymerization processes were stud...The difference between apparent grafting ratio and true grafting ratio in bulk graft copolymerization of styrene onto rubber and the change of rubber particle size during the overall polymerization processes were studied. The results show that, the apparent grafting ratio increased mutationally at the phase inversion and trended to level off after the phase inversion, but the true grating ratio increased gradually with the increase of conversion. At the same time, the particle size of rubber phase in the original polymerizing mixtures almost kept constant after the phase inversion. On the contrary, the size increased with the increase of conversion when the samples were dealt with multi-solution-centrifugation.展开更多
基金Supported by the National Natural Science Foundation of China (No. 29734130).
文摘The bulk polymerization of styrene catalyzed by Nd(P204)3/MgBu2/HMPA (hexamethyl phospho-ramide) was carried out in capped glass tubes. The effects of reaction conditions on polymerization conversion and molecular weight in the range of high conversion were investigated. The molecular weight of the resultant polymers is dramatically high and its distribution is relatively narrow. The polymerization process demonstrates the feature of living polymerization and auto-acceleration phenomenon. The auto-acceleration phenomenon is attributed to the non-instantaneous formation of the active species. The experimental data suggest that chain transfer to MgBu2 is one of the factors governing the molecular weight development. A mechanism of polymerization is presented with the chain transfer process incorporated.
基金supported by the National Natural Science Foundation of China (Nos. 20904036 and 21174094)the Nature Science Key Basic Research of Jiangsu Province for High Education (No. 12KJA150007)Creative Experiment Plan of Soochow University Undergraduates (57315977)
文摘The ＂living＇/controlled radical polymerization （LRP） of styrene （St） at room temperature is rarely reported. In this work, copper（0） （Cu（0））-mediated radical polymerization of St at room temperature was investigated in detail. Dimethyl sulfoxide （DMSO）, N,N-dimethylformamide （DMF） as well as a binary solvent, tetrahydrofuravdl,l,l,3,3,3-hexafluoro-2- propanol were used as the solvents, respectively. Methyl-2-bromopropionate and ethyl 2-bromoisobutyrate were used as the initiators, respectively. The polymerization proceeded smoothly with moderate conversions at room temperature. It was found that DMF was a good solvent with the essential features of LRP, while DMSO was a poor solvent with uncontrollable molecular weights. Besides, the match among the initiator, solvent and molar ratios of reactants can modulate the livingness of the polymerization, and the proper selection of ligand was also crucial to a controlled process. This work provided a first example of Cu（0）-mediated radical polymerization of St at room temperature, which would enrich and strength the LRP technique.
基金Supported by the State Key Polymerization Reaction Engineering Laboratory of Zhejiang University.
文摘A starved feed reactor (SFR) is a semi-batch polymerization reactor where initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. The added initiator decomposes instantaneously and the added monomer polymerizes immediately. The molecular weight (MW) and molecular weight distribution (MWD) of the product polymer can be effectively controlled by the feed ratio of monomer to initiator. This paper presents a study on the MWD of styrene polymerization in a SFR. The MWD model parameters are regressed with experimental data. Although the solids fraction in the SFR is high (higher than 50%), viscosity is not too high and the 'gel effect' is weak due to the low molecular weight of the products. It is found that the termination rate constant is a power function of molecular weight, radicals terminate via 100% combination, the thermal initiation can be neglected even at high reaction temperature studied. And calculated results indicate that in the SFR, the validity of the long chain assumption becomes doubted. It appears that other alterative assumption should be found for an improved model.
文摘The behaviour of water soluble and monomer soluble inhibitors in emulsion polymerization of monomersfollowing Case Ⅱ kinetics(e.g.styrene)has been investigated.Experimental studies reveal that inhibitors canhave an appreciable effect on both polymer particle nucleation and growth.A mathematical model showingthese effects has been developed and simulation studies have been done.The simulation results imply that theconsequences of these effects of monomer soluble inhibitors for industrial emulsion polymerization may be quiteserious.
文摘The difference between apparent grafting ratio and true grafting ratio in bulk graft copolymerization of styrene onto rubber and the change of rubber particle size during the overall polymerization processes were studied. The results show that, the apparent grafting ratio increased mutationally at the phase inversion and trended to level off after the phase inversion, but the true grating ratio increased gradually with the increase of conversion. At the same time, the particle size of rubber phase in the original polymerizing mixtures almost kept constant after the phase inversion. On the contrary, the size increased with the increase of conversion when the samples were dealt with multi-solution-centrifugation.
