The driven polymer translocation through a nanopore with unbiased initial configuration has been studied by using Langevin dynamics(LD) simulations.It is found that the scaling relationship between translocation time ...The driven polymer translocation through a nanopore with unbiased initial configuration has been studied by using Langevin dynamics(LD) simulations.It is found that the scaling relationship between translocation time and the polymer chain length is strongly affected by the friction coefficient in LD and the driving force.However,there is no scaling relationship between the translocation time and the friction coefficient.The translocation time is almost inversely proportional to the driving force,which is in agreement with those obtained in biased translocation.The scaling relationship between gyration radius(R g) of subchain at the trans side with the subchain length(L) is R g ～L 0.33 that is in good agreement with the limiting value for molten globule state,while the curve of R g of subchain at the cis side has two distinct stages.During translocation,the subchain at the cis side is being stretched gradually,and the structure of the subchain transforms from sphere-like to rod-like.When the effect of stretching reaches the tail end,the subchain is at the most stretched state.Finally the subchain will rapidly restore to coil structure.According to the results of force analysis,the retarding force at the trans side is more crucial during the practical translocation.展开更多
High-temperature proton exchange membrane(HT-PEM)fuel cells offer more advantages than low-temperature PEM fuel cells.The ideal characteristics of HT-PEMs are high conductivities,low-humidity operation conditions,adeq...High-temperature proton exchange membrane(HT-PEM)fuel cells offer more advantages than low-temperature PEM fuel cells.The ideal characteristics of HT-PEMs are high conductivities,low-humidity operation conditions,adequate mechanical properties,and competitive costs.Various molecular moieties,such as benzimidazole,benzothiazole,imide,and ether ether ketone,have been introduced to polymer chain backbones to satisfy the application requirements for HT-PEMs.The most common sulfonated polymers based on the main chain backbones have been employed to improve the rties.Side group/chain engineering,including the introduction of SO_(3)^(-) on the side chain,grafting,branching,and crosslinking,has been widely applied to HTPEMs to further improve their proton conductivity,thermal stability,and mechanical properties.Currently,phosphoric acid-doped polybenzimidazole is the most successful polymer material for application in HT-PEMs.The compositing/blending modification methods of polymers are effective in obtaining high PA-doping levels and superior mechanical properties.In this review,the current progress of various membrane materials used for HT-PEMs is summarized.The synthesis and performance characteristics of polymers containing specific moieties in the chain backbones applied to HT-PEMs are discussed systemically.Various modification approaches and their deficiencies associated with HT-PEMs are analyzed and clarified.Prospects and future challenges are also presented.展开更多
In recent years, with the rapid development of polymer science, the application of classical named reactions has transferred from small-molecule compounds to polymers. The versatility of named reactions in terms of mo...In recent years, with the rapid development of polymer science, the application of classical named reactions has transferred from small-molecule compounds to polymers. The versatility of named reactions in terms of monomer selection, solvent environment, reaction temperature, and post-modification permits the synthesis of sophisticated macromolecular structures under conditions where other reaction processes will not operate. In this review, we divided the named reactions employed in polymer-chain synthesis into three types: transition metal-catalyzed cross-coupling reactions, metal-free cross-coupling reactions, and multi-components reactions. Thus, we focused our discussion on the progress in the utilization of these named reactions in polymer synthesis.展开更多
基金Supported by the National Natural Science Foundation of China (20736002, 20706013)the Open Project of the State Key Laboratory of Chemical Engineering ECUST (SKL-ChE-09C02)the Natural Science Fund of the Education Department of Anhui Province (KJ2011B116)
文摘The driven polymer translocation through a nanopore with unbiased initial configuration has been studied by using Langevin dynamics(LD) simulations.It is found that the scaling relationship between translocation time and the polymer chain length is strongly affected by the friction coefficient in LD and the driving force.However,there is no scaling relationship between the translocation time and the friction coefficient.The translocation time is almost inversely proportional to the driving force,which is in agreement with those obtained in biased translocation.The scaling relationship between gyration radius(R g) of subchain at the trans side with the subchain length(L) is R g ～L 0.33 that is in good agreement with the limiting value for molten globule state,while the curve of R g of subchain at the cis side has two distinct stages.During translocation,the subchain at the cis side is being stretched gradually,and the structure of the subchain transforms from sphere-like to rod-like.When the effect of stretching reaches the tail end,the subchain is at the most stretched state.Finally the subchain will rapidly restore to coil structure.According to the results of force analysis,the retarding force at the trans side is more crucial during the practical translocation.
基金supported by the National Key Research and Development Program of China(2019YFC1906602)the National Natural Science Foundation of China(U1904171)+3 种基金the Foundation for"Talent Program"the Open Fund of the State Key Laboratory of Biochemical Engineering,Institute of Process Engineering(IPE)Chinese Academy of Sciences(CAS),the Project Fund of Jiangsu Bingcheng Hydrogen Energy Technology Co.,Ltd.the Young Backbone Teachers Training Program Foundation of Henan University of Technology。
文摘High-temperature proton exchange membrane(HT-PEM)fuel cells offer more advantages than low-temperature PEM fuel cells.The ideal characteristics of HT-PEMs are high conductivities,low-humidity operation conditions,adequate mechanical properties,and competitive costs.Various molecular moieties,such as benzimidazole,benzothiazole,imide,and ether ether ketone,have been introduced to polymer chain backbones to satisfy the application requirements for HT-PEMs.The most common sulfonated polymers based on the main chain backbones have been employed to improve the rties.Side group/chain engineering,including the introduction of SO_(3)^(-) on the side chain,grafting,branching,and crosslinking,has been widely applied to HTPEMs to further improve their proton conductivity,thermal stability,and mechanical properties.Currently,phosphoric acid-doped polybenzimidazole is the most successful polymer material for application in HT-PEMs.The compositing/blending modification methods of polymers are effective in obtaining high PA-doping levels and superior mechanical properties.In this review,the current progress of various membrane materials used for HT-PEMs is summarized.The synthesis and performance characteristics of polymers containing specific moieties in the chain backbones applied to HT-PEMs are discussed systemically.Various modification approaches and their deficiencies associated with HT-PEMs are analyzed and clarified.Prospects and future challenges are also presented.
基金supported by the National Natural Science Foundation of China(21174158,21274162,21474127)Shanghai Scientific and Technological Innovation Project(12JC1410500,13ZR1464800,14QA1404500,14520720100)the State Key Laboratory of Molecular Engineering of Polymers(K2015-02)
文摘In recent years, with the rapid development of polymer science, the application of classical named reactions has transferred from small-molecule compounds to polymers. The versatility of named reactions in terms of monomer selection, solvent environment, reaction temperature, and post-modification permits the synthesis of sophisticated macromolecular structures under conditions where other reaction processes will not operate. In this review, we divided the named reactions employed in polymer-chain synthesis into three types: transition metal-catalyzed cross-coupling reactions, metal-free cross-coupling reactions, and multi-components reactions. Thus, we focused our discussion on the progress in the utilization of these named reactions in polymer synthesis.
