Polystyrene-styrene/butadiene diblock copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization.During the polymerization process,the molecular weight distri...Polystyrene-styrene/butadiene diblock copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization.During the polymerization process,the molecular weight distribution was narrow and the numerical molecular weight of the copolymers increased with increasing conversion of monomers,which was close to the theoretical.FT-IR and ^1H NMR results indicated that the microstructure of the polymer was mainly 1,4-trans-butadiene with small amount of 1,2-units,and composition in the copolymers was obtained.展开更多
Reversible addition-fragmentation transfer (RAPT) miniemulsion polymerizations for PMMA with cumyl dithiobenzoate (CDB) as a chain transfer agent (CTA) has been carried out. Higher temperature made the polymeriz...Reversible addition-fragmentation transfer (RAPT) miniemulsion polymerizations for PMMA with cumyl dithiobenzoate (CDB) as a chain transfer agent (CTA) has been carried out. Higher temperature made the polymerization much faster and the PDI remained below 1.20, when the temperature was upon 70 ℃.展开更多
Reversible addition-fragmentation chain transfer(RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate)(PE/PET) composite fibers was performed using γ-irradiation as the initial sourc...Reversible addition-fragmentation chain transfer(RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate)(PE/PET) composite fibers was performed using γ-irradiation as the initial source at ambient temperature. Different initial concentrations of 2-cyanoprop-2-yl dithiobenzonate were used as the chain transfer agent. The kinetics of graft polymerization is in accordance with the living RAFT polymerization. The successful grafting of acrylonitrile is proved by Fourier transform infrared spectroscopy analysis.The results of monofilament tensile test show that mechanical properties of the fibers change slightly after grafting. Scanning electronic microscopy images of the fibers show that the surface of RAFT grafted fibers is smoother than that of fibers grafted conventionally.展开更多
Bulk polymerization of styrene was carried out in the presence of a reversible addition fragmentation chain transfer (RAFT) of benzyl dithiobenzoate (BDB). The comparison between reaction systems with and without BDB ...Bulk polymerization of styrene was carried out in the presence of a reversible addition fragmentation chain transfer (RAFT) of benzyl dithiobenzoate (BDB). The comparison between reaction systems with and without BDB indicates that there is significant retardation in the reaction rate when BDB is used. The molecular weight of styrene polymer prepared with BDB shows linear relationship with the conversion of monomer, polydispersity is as narrow as 1.2, and no gel effects are observed during the polymerization with BDB, which are characteristics of a living radical polymerization. It has been found that the concentrations of BDB and azobis (isobutyronitrile) (AIBN) have opposite effects on the polymerization kinetics, and the AIBN dominates.展开更多
Usually,the aniline-based late-transition-metal catalysts often require bulky steric substituents on both sides of the ortho-aryl position to achieve efficient suppression of chain transfer in ethylene polymerization....Usually,the aniline-based late-transition-metal catalysts often require bulky steric substituents on both sides of the ortho-aryl position to achieve efficient suppression of chain transfer in ethylene polymerization.In this contribution,we demonstrated thatα-diimine catalysts based on naphthylamine with only one bulky ortho-aryl substituent also demonstrated excellent capabilities to suppress the chain transfer.Firstly,a class ofα-diimine nickel and palladium complexes with only one o-aryl-dibenzhydryl or o-aryl-dibenzosuberyl substituent were synthesized and characterized.Secondly,the as-prepared naphthylamine-based nickel catalysts demonstrated outstanding activities(up to 13.02×106 g·mol–1·h–1)and yielded lightly branched(16-40/1000C)polyethylenes with very high molecular weights(445.8-854.3 kg/mol)in ethylene polymerization.In comparison,the corresponding palladium catalysts showed moderate activities(level of 104-105 g·mol–1·h–1),generating moderately branched(47-78/1000C)polyethylenes with moderate molecular weights(21.6-82.0 kg/mol).Moreover,the palladium catalysts could also copolymerize ethylene and methyl acrylate(MA),albeit in low activities(level of 103 g·mol–1·h–1),providing E-MA copolymers with low to moderate molecular weights(1.4-16.3 kg/mol)and a moderate level of incorporation ratio(2.4-7.4 mol%)and branching density(53-84/1000C).As compared with aniline-based nickel and palladium catalysts,the naphthylamine-based catalysts displayed a superior ability to suppress the chain transfer reactions and could give access to(co)polymers with orders of magnitude higher molecular weight in ethylene(co)polymerization.展开更多
Through neodymium-mediated coordinative chain transfer copolymerizaiton(CCTcoP),polyisoprenes bearing dual hydroxylated mini-blocky chain-ends were prepared via a three-step strategy.Kinetic studies revealed that,the ...Through neodymium-mediated coordinative chain transfer copolymerizaiton(CCTcoP),polyisoprenes bearing dual hydroxylated mini-blocky chain-ends were prepared via a three-step strategy.Kinetic studies revealed that,the polymerization demonstrated typical features of CCTcoP across the whole polymerization process,i.e.,quasi-living polymerization characteristic,tunable molecular weights,narrow molecular weight distributions,and atom economies.Comparing to previously reported CCTP homopolymerization systems,the presence of oxygen-containing IpOAl polar comonomer slowed down chain transfer rates obviously,rendering slightly higher molecular weights of the resultant PIps and smaller Np(number of polymer chains per Nd atom)values.Moreover,to mimic the structure of natural rubber,the hydroxyl end groups can be facilely modified into phosphonate,amide,and UPy,whose structures were further confirmed by NMR spectra.Incorporation these functionalities could greatly improve the hydrophilic properties of the polymers,as revealed from the significantly reduced static water contact angles.展开更多
In this paper, three different kinds of β-CD derivatives were synthesized as atom transfer radical polymerization(ATRP) initiator or reversible addition-fragmentation chain transfer polymerization(RAFT) chain tra...In this paper, three different kinds of β-CD derivatives were synthesized as atom transfer radical polymerization(ATRP) initiator or reversible addition-fragmentation chain transfer polymerization(RAFT) chain transfers. The degree of substitution for each derivative was carefully characterized through 1H-NMR, 13C-NMR spectroscopy and matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF-MS). The factors influencing the degree of substitution were discussed. Moreover, the comparison between ATRP and RAFT was shown in the polymerization of Nisopropyl acrylamide(NIPAM).展开更多
The dependence of the molecular weights on the concentration of reactants in the polymerization of acrylonitrile initiated by vanadium (V)-thiourea redox system has been investigated. It was found that the molecular w...The dependence of the molecular weights on the concentration of reactants in the polymerization of acrylonitrile initiated by vanadium (V)-thiourea redox system has been investigated. It was found that the molecular weights of the polymer change nonlinearly with increasing concentrations of nitric acid and thiourea. Probably, the composition of the complexes exert a great influence on the chain initiation and termination. The reaction of 'complextermination' gives rise to the decrease of the molecular weights markedly while the concentrations of thiourea and vanadium (V)in the range from one to three molar ratios.展开更多
Effective molecularly imprinted membranes(MIMs) were developed as an efficient adsorbent for the selective removal ofp-hydroxybenzoic acid(p-HB) from acetylsalicylic acid(ASA, aspirin). The MIMs were grafted suc...Effective molecularly imprinted membranes(MIMs) were developed as an efficient adsorbent for the selective removal ofp-hydroxybenzoic acid(p-HB) from acetylsalicylic acid(ASA, aspirin). The MIMs were grafted successfully from poly(vinylidene fluoride) microfiltration membranes via reversible addition-fragmentation chain transfer(RAFT) polymerization. The graft copolymerization of acrylic acid(AA) in the presence of template p-hydroxybenzoic acid led to molecularly imprinted polymer(MIP) film coated membranes. The obtained MIMs were characterized by scanning electron microscopy(SEM), Fourier transform infrared spectrophotometer(FTIR) and Raman spectra, and batch mode adsorption studies were carried ont to investigate the specific adsorption equilibrium, kinetics and selective recognition properties of different MIMs. The kinetic properties of the MIMs could be well described by the pseudo-second-order rate equation. Selective permeation experiments were performed to evaluate the permeation selectivity of the p-HB imprinted membranes. The observed performances of the MIMs are applicable to the further purification of aspirin. Keywords Acetylsalicylic acid; Reversible addition-fragmentation chain transfer; Molecularly imprinted membrane; p-Hydroxybenzoic acid; Selective adsorption展开更多
Reversible chain transfer catalyzed polymerization(RTCP)is a practical and efficient process for the precise synthesis of polymers with special architecture by using simple phenols(2,4,6-trimethylphenol,TMP)or hydroca...Reversible chain transfer catalyzed polymerization(RTCP)is a practical and efficient process for the precise synthesis of polymers with special architecture by using simple phenols(2,4,6-trimethylphenol,TMP)or hydrocarbons(xanthene,XT)as efficient organocatalysts.Herein,alkyl iodide(R-1),which was gen erated from in situ bromine-iodine transformation of alkyl bromide(R-Br)with sodium iodide(Nal),was served as initiator to mediate RTCP with TMP or XT.MMA and other functional methacrylates,including GMA,DEAM,DMAEMA and BzMA,were successfully initiated by combining orga no catalysts and azo in itiators to yield polymers with low-polydispersity(M_(w)/M_(n)=1.1-1.5)and ideal mono mer conversions(50%-90%)at moderate temperature.More over,3-armstar polymers were also obtained by this method.The high chain-end fidelity of the obtained poly(methyl methacrylate)with iodine as chain-end group(PMMA-I)was confirmed by chain-extension reaction.The en vironme ntally frie ndly initiators and orga no catalysts exhibit powerful polymerization properties toward RTCP,providing a sign ificant method to synthesize functional polymers.展开更多
Tremendous advances has been witnessed in the past few years in the lanthanide complexes mediated coordinative chain transfer polymerization(CCTP) of conjugated dienes. CCTP features catalyst economy, well-controlling...Tremendous advances has been witnessed in the past few years in the lanthanide complexes mediated coordinative chain transfer polymerization(CCTP) of conjugated dienes. CCTP features catalyst economy, well-controlling over both microstructure and architecture of the resulting polymers, and accessibility for novel(co)polymers. This review highlights the recent progresses made in the field of CCTP of dienes. After a brief introduction, the body of this review is divided into three parts:(1) principle of CCTP;(2) coordinative chain transfer homopolymerization of dienes;(3) coordinative chain transfer copolymerization of dienes.At the end, we present some challenges remaining in this area and our personal opinion regarding where this field should continue to develop. CCTP represents a novel strategy to prepare polydiene synthetic rubbers with controlled high molecular weight and narrow molecular weight distribution, which has reached the practical industrial application level, demonstrating a great potential in industrialization.展开更多
Hg in acid soil could be activited by liming and become available to plant,if excessive or insufficient amount of line was applied.The changes of Hg activity in acid soil with different rates of CaCO3 amendment were s...Hg in acid soil could be activited by liming and become available to plant,if excessive or insufficient amount of line was applied.The changes of Hg activity in acid soil with different rates of CaCO3 amendment were studied by a pot experiment.To predict the adequate amount of lime application,a simple method using the pH(EDTA) as an indicator was suggested.The suitable range of lime application was the amount of lime addition when the pH of soil-EDTA system was raised to 4.0-4.3.展开更多
Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methac...Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent,pentaerythritol tetrakis(3-mercaptopropinate).At appropriate monomer conversions,two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were o...展开更多
The combination of Pt^2+, benzoquinone and NaNO2 forms an electron-transfer chain, which leads to the oxidation of methane by O2 in CF3COOH aqueous solution. The overall turnover number per hour (TOF) of methane at...The combination of Pt^2+, benzoquinone and NaNO2 forms an electron-transfer chain, which leads to the oxidation of methane by O2 in CF3COOH aqueous solution. The overall turnover number per hour (TOF) of methane at 120 ℃ is 0.5 h^-1, however, only about one fourth (23%) of methane is converted to the desired product of methanol in the formation of CF3COOCH3. The over-oxidation of methane to CO2, over the catalyst with the Pt^2+ species immobilized via 2,2'-bipyridyl as a ligand on the silica substrate, is depressed distinctly. Under the same conditions, the conversion to methanol dominates, and no CO2 is observed, on account of the over-oxidation of methane, as confirmed by the isotope experiment.展开更多
In order to satisfy the requirement of SI-traceable on-orbit absolute radiation calibration transfer with high accuracy for satellite remote sensors,a transfer chain consisting of a fiber coupling monochromator(FBM)...In order to satisfy the requirement of SI-traceable on-orbit absolute radiation calibration transfer with high accuracy for satellite remote sensors,a transfer chain consisting of a fiber coupling monochromator(FBM) and an integrating sphere transfer radiometer(ISTR) was designed in this paper.Depending on the Sun,this chain based on detectors provides precise spectral radiometric calibration and measurement to spectrometers in the reflective solar band(RSB) covering 300–2500 nm with a spectral bandwidth of 0.5–6 nm.It shortens the traditional chain based on lamp source and reduces the calibration uncertainty from 5% to 0.5% by using the cryogenic radiometer in space as a radiometric benchmark and trap detectors as secondary standard.This paper also gives a detailed uncertainty budget with reasonable distribution of each impact factor,including the weak spectral signal measurement with uncertainty of 0.28%.According to the peculiar design and comprehensive uncertainty analysis,it illustrates that the spectral radiance measurement uncertainty of the ISTR system can reach to 0.48%.The result satisfies the requirements of SI-traceable on-orbit calibration and has wider significance for expanding the application of the remote sensing data with high-quality.展开更多
As for the factors affecting the heat transfer performance of complex and nonlinear oscillating heat pipe (OHP),grey relational analysis (GRA) was used to deal with the relationship between heat transfer rate of a loo...As for the factors affecting the heat transfer performance of complex and nonlinear oscillating heat pipe (OHP),grey relational analysis (GRA) was used to deal with the relationship between heat transfer rate of a looped copper-water OHP and charging ratio,inner diameter,inclination angel,heat input,number of turns,and the main influencing factors were defined.Then,forecasting model was obtained by using main influencing factors (such as charging ratio,interior diameter,and inclination angel) as the inputs of function chain neural network.The results show that the relative average error between the predicted and actual value is 4%,which illustrates that the function chain neural network can be applied to predict the performance of OHP accurately.展开更多
In this paper, the electronic transfer integrals, the energy gap, and the bandwidth of a planar trans polyacetylene chain are calculated in Wannier representation, in which a combination of the wave function of hydrog...In this paper, the electronic transfer integrals, the energy gap, and the bandwidth of a planar trans polyacetylene chain are calculated in Wannier representation, in which a combination of the wave function of hydrogen like atoms is used to stand for the Wannier function. When the effective nuclear charge number Z = 2.125 and the distortion amplitude of the carbon sites u =0.0038 nm, the nearest, next, and third neighbor hopping energies obtained are -3.224 78 eV, -2.388 61 eV, 0.148 14 eV, 0.006 65 eV, and 0.006 50 eV, respectively. The energy bandwidth and gap corresponding to these values are W d =11.19 eV and E g =1.70 eV, respectively. These results coincide with the experimental values.展开更多
基金supported by Major Program of National Natural Science Foundation of China(No. 20836007)National Natural Science Foundation of China(No.20806067).
文摘Polystyrene-styrene/butadiene diblock copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization.During the polymerization process,the molecular weight distribution was narrow and the numerical molecular weight of the copolymers increased with increasing conversion of monomers,which was close to the theoretical.FT-IR and ^1H NMR results indicated that the microstructure of the polymer was mainly 1,4-trans-butadiene with small amount of 1,2-units,and composition in the copolymers was obtained.
文摘Reversible addition-fragmentation transfer (RAPT) miniemulsion polymerizations for PMMA with cumyl dithiobenzoate (CDB) as a chain transfer agent (CTA) has been carried out. Higher temperature made the polymerization much faster and the PDI remained below 1.20, when the temperature was upon 70 ℃.
基金Supported by the National Natural Science Foundation of China(Nos.11475246 and 11175234)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA02030205)
文摘Reversible addition-fragmentation chain transfer(RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate)(PE/PET) composite fibers was performed using γ-irradiation as the initial source at ambient temperature. Different initial concentrations of 2-cyanoprop-2-yl dithiobenzonate were used as the chain transfer agent. The kinetics of graft polymerization is in accordance with the living RAFT polymerization. The successful grafting of acrylonitrile is proved by Fourier transform infrared spectroscopy analysis.The results of monofilament tensile test show that mechanical properties of the fibers change slightly after grafting. Scanning electronic microscopy images of the fibers show that the surface of RAFT grafted fibers is smoother than that of fibers grafted conventionally.
文摘Bulk polymerization of styrene was carried out in the presence of a reversible addition fragmentation chain transfer (RAFT) of benzyl dithiobenzoate (BDB). The comparison between reaction systems with and without BDB indicates that there is significant retardation in the reaction rate when BDB is used. The molecular weight of styrene polymer prepared with BDB shows linear relationship with the conversion of monomer, polydispersity is as narrow as 1.2, and no gel effects are observed during the polymerization with BDB, which are characteristics of a living radical polymerization. It has been found that the concentrations of BDB and azobis (isobutyronitrile) (AIBN) have opposite effects on the polymerization kinetics, and the AIBN dominates.
基金supported by Natural Science Foundation of Anhui Province(2108085Y06)Anhui Provincial Key Laboratory Open Project Foundation(LCECSC-01)Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology(BM2012110).
文摘Usually,the aniline-based late-transition-metal catalysts often require bulky steric substituents on both sides of the ortho-aryl position to achieve efficient suppression of chain transfer in ethylene polymerization.In this contribution,we demonstrated thatα-diimine catalysts based on naphthylamine with only one bulky ortho-aryl substituent also demonstrated excellent capabilities to suppress the chain transfer.Firstly,a class ofα-diimine nickel and palladium complexes with only one o-aryl-dibenzhydryl or o-aryl-dibenzosuberyl substituent were synthesized and characterized.Secondly,the as-prepared naphthylamine-based nickel catalysts demonstrated outstanding activities(up to 13.02×106 g·mol–1·h–1)and yielded lightly branched(16-40/1000C)polyethylenes with very high molecular weights(445.8-854.3 kg/mol)in ethylene polymerization.In comparison,the corresponding palladium catalysts showed moderate activities(level of 104-105 g·mol–1·h–1),generating moderately branched(47-78/1000C)polyethylenes with moderate molecular weights(21.6-82.0 kg/mol).Moreover,the palladium catalysts could also copolymerize ethylene and methyl acrylate(MA),albeit in low activities(level of 103 g·mol–1·h–1),providing E-MA copolymers with low to moderate molecular weights(1.4-16.3 kg/mol)and a moderate level of incorporation ratio(2.4-7.4 mol%)and branching density(53-84/1000C).As compared with aniline-based nickel and palladium catalysts,the naphthylamine-based catalysts displayed a superior ability to suppress the chain transfer reactions and could give access to(co)polymers with orders of magnitude higher molecular weight in ethylene(co)polymerization.
基金financially supported by the National Natural Science Foundation of China(No.U1862206)Jilin Province Department of Education(No.JJKH20200665KJ)+3 种基金Dr.W.Zhao thanks for the financial support from China Postdoctoral Science Foundation(No.2021M701818)Shandong Provincial Natural Science Foundation,China(No.ZR2022QE237)Qingdao Postdoctoral Applied Research Project,PetroChina Company Limited(No.2020B-2711)H.Liu sincerely acknowledges the financial support from the Taishan Scholars Program。
文摘Through neodymium-mediated coordinative chain transfer copolymerizaiton(CCTcoP),polyisoprenes bearing dual hydroxylated mini-blocky chain-ends were prepared via a three-step strategy.Kinetic studies revealed that,the polymerization demonstrated typical features of CCTcoP across the whole polymerization process,i.e.,quasi-living polymerization characteristic,tunable molecular weights,narrow molecular weight distributions,and atom economies.Comparing to previously reported CCTP homopolymerization systems,the presence of oxygen-containing IpOAl polar comonomer slowed down chain transfer rates obviously,rendering slightly higher molecular weights of the resultant PIps and smaller Np(number of polymer chains per Nd atom)values.Moreover,to mimic the structure of natural rubber,the hydroxyl end groups can be facilely modified into phosphonate,amide,and UPy,whose structures were further confirmed by NMR spectra.Incorporation these functionalities could greatly improve the hydrophilic properties of the polymers,as revealed from the significantly reduced static water contact angles.
基金financially supported by the National Natural Science Foundation of China(Nos.21174076 and 21374053)
文摘In this paper, three different kinds of β-CD derivatives were synthesized as atom transfer radical polymerization(ATRP) initiator or reversible addition-fragmentation chain transfer polymerization(RAFT) chain transfers. The degree of substitution for each derivative was carefully characterized through 1H-NMR, 13C-NMR spectroscopy and matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF-MS). The factors influencing the degree of substitution were discussed. Moreover, the comparison between ATRP and RAFT was shown in the polymerization of Nisopropyl acrylamide(NIPAM).
文摘The dependence of the molecular weights on the concentration of reactants in the polymerization of acrylonitrile initiated by vanadium (V)-thiourea redox system has been investigated. It was found that the molecular weights of the polymer change nonlinearly with increasing concentrations of nitric acid and thiourea. Probably, the composition of the complexes exert a great influence on the chain initiation and termination. The reaction of 'complextermination' gives rise to the decrease of the molecular weights markedly while the concentrations of thiourea and vanadium (V)in the range from one to three molar ratios.
基金Supported by the National Natural Science Foundation of China(No.21606099), the Natural Science Foundation of Jilin Province, China(No.20180623042TC) and the Science and Technology Research Foundation of the Department of Education of Jilin Province, China(Nos. JJKH20180 782KJ, JJKH20180761K J, JJKH20170376K J).
文摘Effective molecularly imprinted membranes(MIMs) were developed as an efficient adsorbent for the selective removal ofp-hydroxybenzoic acid(p-HB) from acetylsalicylic acid(ASA, aspirin). The MIMs were grafted successfully from poly(vinylidene fluoride) microfiltration membranes via reversible addition-fragmentation chain transfer(RAFT) polymerization. The graft copolymerization of acrylic acid(AA) in the presence of template p-hydroxybenzoic acid led to molecularly imprinted polymer(MIP) film coated membranes. The obtained MIMs were characterized by scanning electron microscopy(SEM), Fourier transform infrared spectrophotometer(FTIR) and Raman spectra, and batch mode adsorption studies were carried ont to investigate the specific adsorption equilibrium, kinetics and selective recognition properties of different MIMs. The kinetic properties of the MIMs could be well described by the pseudo-second-order rate equation. Selective permeation experiments were performed to evaluate the permeation selectivity of the p-HB imprinted membranes. The observed performances of the MIMs are applicable to the further purification of aspirin. Keywords Acetylsalicylic acid; Reversible addition-fragmentation chain transfer; Molecularly imprinted membrane; p-Hydroxybenzoic acid; Selective adsorption
基金We gratefully acknowledge the financial support from Natural Science Foundation of Fujian Province(No.2019J05040)Key Program of Qingyuan Innovation Laboratory(No.00221003)‘111'program and Talent program of Fuzhou University(No.GXRC-18041).
文摘Reversible chain transfer catalyzed polymerization(RTCP)is a practical and efficient process for the precise synthesis of polymers with special architecture by using simple phenols(2,4,6-trimethylphenol,TMP)or hydrocarbons(xanthene,XT)as efficient organocatalysts.Herein,alkyl iodide(R-1),which was gen erated from in situ bromine-iodine transformation of alkyl bromide(R-Br)with sodium iodide(Nal),was served as initiator to mediate RTCP with TMP or XT.MMA and other functional methacrylates,including GMA,DEAM,DMAEMA and BzMA,were successfully initiated by combining orga no catalysts and azo in itiators to yield polymers with low-polydispersity(M_(w)/M_(n)=1.1-1.5)and ideal mono mer conversions(50%-90%)at moderate temperature.More over,3-armstar polymers were also obtained by this method.The high chain-end fidelity of the obtained poly(methyl methacrylate)with iodine as chain-end group(PMMA-I)was confirmed by chain-extension reaction.The en vironme ntally frie ndly initiators and orga no catalysts exhibit powerful polymerization properties toward RTCP,providing a sign ificant method to synthesize functional polymers.
基金supported by the National Key R&D Program of China(Grant Nos.2017YFB0307100,2017YFB0307103)the National Basic Research Program of China(Grant Nos.2015CB654700,2015CB654702)
文摘Tremendous advances has been witnessed in the past few years in the lanthanide complexes mediated coordinative chain transfer polymerization(CCTP) of conjugated dienes. CCTP features catalyst economy, well-controlling over both microstructure and architecture of the resulting polymers, and accessibility for novel(co)polymers. This review highlights the recent progresses made in the field of CCTP of dienes. After a brief introduction, the body of this review is divided into three parts:(1) principle of CCTP;(2) coordinative chain transfer homopolymerization of dienes;(3) coordinative chain transfer copolymerization of dienes.At the end, we present some challenges remaining in this area and our personal opinion regarding where this field should continue to develop. CCTP represents a novel strategy to prepare polydiene synthetic rubbers with controlled high molecular weight and narrow molecular weight distribution, which has reached the practical industrial application level, demonstrating a great potential in industrialization.
文摘Hg in acid soil could be activited by liming and become available to plant,if excessive or insufficient amount of line was applied.The changes of Hg activity in acid soil with different rates of CaCO3 amendment were studied by a pot experiment.To predict the adequate amount of lime application,a simple method using the pH(EDTA) as an indicator was suggested.The suitable range of lime application was the amount of lime addition when the pH of soil-EDTA system was raised to 4.0-4.3.
文摘Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent,pentaerythritol tetrakis(3-mercaptopropinate).At appropriate monomer conversions,two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were o...
基金Ministry of Science and Technology of China (2005CB221405)
文摘The combination of Pt^2+, benzoquinone and NaNO2 forms an electron-transfer chain, which leads to the oxidation of methane by O2 in CF3COOH aqueous solution. The overall turnover number per hour (TOF) of methane at 120 ℃ is 0.5 h^-1, however, only about one fourth (23%) of methane is converted to the desired product of methanol in the formation of CF3COOCH3. The over-oxidation of methane to CO2, over the catalyst with the Pt^2+ species immobilized via 2,2'-bipyridyl as a ligand on the silica substrate, is depressed distinctly. Under the same conditions, the conversion to methanol dominates, and no CO2 is observed, on account of the over-oxidation of methane, as confirmed by the isotope experiment.
基金Project supported by the National Natural Science Foundation of China(Grant No.41474161)the National High-Technology Program of China(Grant No.2015AA123703)
文摘In order to satisfy the requirement of SI-traceable on-orbit absolute radiation calibration transfer with high accuracy for satellite remote sensors,a transfer chain consisting of a fiber coupling monochromator(FBM) and an integrating sphere transfer radiometer(ISTR) was designed in this paper.Depending on the Sun,this chain based on detectors provides precise spectral radiometric calibration and measurement to spectrometers in the reflective solar band(RSB) covering 300–2500 nm with a spectral bandwidth of 0.5–6 nm.It shortens the traditional chain based on lamp source and reduces the calibration uncertainty from 5% to 0.5% by using the cryogenic radiometer in space as a radiometric benchmark and trap detectors as secondary standard.This paper also gives a detailed uncertainty budget with reasonable distribution of each impact factor,including the weak spectral signal measurement with uncertainty of 0.28%.According to the peculiar design and comprehensive uncertainty analysis,it illustrates that the spectral radiance measurement uncertainty of the ISTR system can reach to 0.48%.The result satisfies the requirements of SI-traceable on-orbit calibration and has wider significance for expanding the application of the remote sensing data with high-quality.
基金Project(531107040300) supported by the Fundamental Research Funds for the Central Universities in ChinaProject(2006BAJ04B04) supported by the National Science and Technology Pillar Program during the Eleventh Five-year Plan Period of China
文摘As for the factors affecting the heat transfer performance of complex and nonlinear oscillating heat pipe (OHP),grey relational analysis (GRA) was used to deal with the relationship between heat transfer rate of a looped copper-water OHP and charging ratio,inner diameter,inclination angel,heat input,number of turns,and the main influencing factors were defined.Then,forecasting model was obtained by using main influencing factors (such as charging ratio,interior diameter,and inclination angel) as the inputs of function chain neural network.The results show that the relative average error between the predicted and actual value is 4%,which illustrates that the function chain neural network can be applied to predict the performance of OHP accurately.
基金The project supported by National Natural Science Foundation of China under Grant No. 10474104 and the National Fundamental Research Program of China under Grant No. 2001CB309310
文摘In this paper, the electronic transfer integrals, the energy gap, and the bandwidth of a planar trans polyacetylene chain are calculated in Wannier representation, in which a combination of the wave function of hydrogen like atoms is used to stand for the Wannier function. When the effective nuclear charge number Z = 2.125 and the distortion amplitude of the carbon sites u =0.0038 nm, the nearest, next, and third neighbor hopping energies obtained are -3.224 78 eV, -2.388 61 eV, 0.148 14 eV, 0.006 65 eV, and 0.006 50 eV, respectively. The energy bandwidth and gap corresponding to these values are W d =11.19 eV and E g =1.70 eV, respectively. These results coincide with the experimental values.