Surface patterning was aroused much interest because of its great importance in the applications to microfluidic devices, etc. In this paper, we report a novel method to realize surface patterning on an electro-sensit...Surface patterning was aroused much interest because of its great importance in the applications to microfluidic devices, etc. In this paper, we report a novel method to realize surface patterning on an electro-sensitive polymerpoly(2-acrylamido-2-methylpropanesulfonic acid). Through imposing the external electrical field utilizing a copper mesh film used in SEM as electrode, the film exhibits different properties in the areas that contact or not contact with the metal part of the mesh, which resulting in a pattern being the same as the mesh. This effect can be well explained by the conformational change of the polymer chains in the electric field.展开更多
The coil-to-globule transition of thermally sensitive linear poly（N-isopropylacrylamide） （PNIPAM） labeled with dansyl group is induced by 1.54 μm laser pulses （widths10 ns）. The dansyl group is used to follow t...The coil-to-globule transition of thermally sensitive linear poly（N-isopropylacrylamide） （PNIPAM） labeled with dansyl group is induced by 1.54 μm laser pulses （widths10 ns）. The dansyl group is used to follow the transition kinetics because its fluorescence intensity is very sensitive to its micro-environment. As the molar ratio of NIPAM monomer to dansyl group increases from 110 to 300, the effect of covalently attached dansyl fluorophores on the transition decreases. In agreement with our previous study in which we used 8-anilino- l-naphthalensulfonic acid ammonium salt free in water as a fluorescent probe, the current study reveals that the transition has two distinct stages with two characteristic times, namely, Tfast≈0.1 ms, which can be attributed to the nucleation and formation of some ＂pearls＂ （locally contracting segments） on the chain, and tslow≈0.5 ms, which is related to the merging and coarsening of the ＂pearls＂.Tfast is independent of the PNIPAM chain length over a wide range （Mw=2.8× 10^6-4.2 × 10^7 g/mol）. On the other hand, Tslow only slightly increases with the chain length.展开更多
Ultra‐small metal nanoclusters have high surface energy and abundant active sites,and thereforetheir catalytic activities are usually significantly higher than those of larger nanoparticles.A temperature‐responsive ...Ultra‐small metal nanoclusters have high surface energy and abundant active sites,and thereforetheir catalytic activities are usually significantly higher than those of larger nanoparticles.A temperature‐responsive copolymer,namely poly(ethylene glycol)‐co‐poly(N‐isopropylacrylamide)(PEG‐PNIPAM)was synthesized as the first step,and then ultra‐small Pd clusters stabilized withinPEG‐PNIPAM copolymer micelles were formed by direct reduction.Pd nanoclusters of size less than2nm showed outstanding catalytic activity in the Suzuki coupling reaction.The reaction betweeniodobenzene and phenylboronic acid was completed in as little as10s(turnover frequency=4.3×104h?1).A yield of64%was achieved in5min in the reaction between chlorobenzene and phenylboronicacid.The catalyst showed significant deactivation during three consecutive runs.However,this composite catalyst consisting of Pd/PEG‐PNIPAM can be easily recycled based on the reversiblephase transition of temperature‐responsive PEG‐PNIPAM.This catalyst therefore has good potentialfor practical applications.展开更多
The main objective of this work is to propose new mixture response parameters and to compare correlations with rut depths and sensitivity of permanent deformation response parameters based on field extracted cores and...The main objective of this work is to propose new mixture response parameters and to compare correlations with rut depths and sensitivity of permanent deformation response parameters based on field extracted cores and lab-mixed duplicates. A new "mix-confined" test is developed and four new parameters for this test are proposed. Correlation coefficients with rut depths and coefficients of variation (sensitivity) are compared between the four new and two existing parameters. Some parameters are recommended to be used for the newly developed test. The results show that, newly developed test can capture the changes of permanent deformation of asphalt mixtures. Only one new parameter (D1 of Stephen Price model) and one existing parameter (flow number, Fn ) have strong correlations with rut depths of asphalt pavements (R2 greater than 0.7) and have relative small sensitivity (coefficient of variation, COV, less than 30%). For polymer modified asphalt mixtures, the parameter D1 rather than Fn should be used. These findings can be used to check the permanent deformation of asphalt mixture during the mix design.展开更多
We report on the fabrication of fluorescent and multicolor probes for Zn^2＋ ions and temperature from a mixture of three types of fluorophore-labeled responsive block copolymers in aqueous media. Quinoline-based Zn^2...We report on the fabrication of fluorescent and multicolor probes for Zn^2＋ ions and temperature from a mixture of three types of fluorophore-labeled responsive block copolymers in aqueous media. Quinoline-based Zn^2＋-recognizing fluorescent mono- mer ZQMA, red-emitting rhodamine B-based monomer RhBEA, and blue-emitting coumarin derivative Coum-OH, were syn- thesized first. A ZQMA-labeled well-defined double hydrophilic block copolymer （DHBC）, PEG-b-P（MEO2MA-co-ZQMA）, was synthesized via reversible addition-fragmentation chain-transfer （RAFT） polymerization of 2-（2-methoxyethoxy）ethyl methacrylate （MEOzMA） and ZQMA by utilizing a PEG-based macroRAFT agent. Following similar procedures, PEG-b-P（St-co-RhBEA） amphiphilic diblock copolymer and PEG-b-P（MEOzMA-co-Coum） DHBC were also synthesized, where P（St-co-RhBEA） was a RhBEA-labeled polystyrene （PS） block. At room temperature in aqueous solution, almost non- fluorescent PEG-b-P（MEOzMA-co-ZQMA） can effectively bind Zn2＋ ions, leading to prominent green fluorescence enhance- ment due to the coordination of ZQMA with Zn^2＋ ions. However, by mixing red-emitting PEG-b-P（St-co-RhBEA） and blue-emitting PEG-b-P（MEO2MA-co-Coum） with PEG-b-P（MEO2MA-co-ZQMA） at an appropriate ratio, three color transitions could be observed. In the absence of Zn^2＋ ions, a mixed pink fluorescent originating from Coum and RhBEA was ob- served; upon the addition of a certain amount of Zn^2＋ ions, the green fluorescence enhanced dramatically, leading to a white fluorescence readout. By further increasing the amount of Zn2＋ ions, the green fluorescence further enhanced and overwhelmed the blue and red emissions, leading to a green-dominant mixed-fluorescence emission. In addition, upon increasing the temperature, the fluorescence of Coum decreased considerably due to the fluorescence-resonance energy transfer （FRET） between Coum and ZQMA moieties. In this way, a ratiometric fluorescent thermometer can be constructed.展开更多
文摘Surface patterning was aroused much interest because of its great importance in the applications to microfluidic devices, etc. In this paper, we report a novel method to realize surface patterning on an electro-sensitive polymerpoly(2-acrylamido-2-methylpropanesulfonic acid). Through imposing the external electrical field utilizing a copper mesh film used in SEM as electrode, the film exhibits different properties in the areas that contact or not contact with the metal part of the mesh, which resulting in a pattern being the same as the mesh. This effect can be well explained by the conformational change of the polymer chains in the electric field.
文摘The coil-to-globule transition of thermally sensitive linear poly（N-isopropylacrylamide） （PNIPAM） labeled with dansyl group is induced by 1.54 μm laser pulses （widths10 ns）. The dansyl group is used to follow the transition kinetics because its fluorescence intensity is very sensitive to its micro-environment. As the molar ratio of NIPAM monomer to dansyl group increases from 110 to 300, the effect of covalently attached dansyl fluorophores on the transition decreases. In agreement with our previous study in which we used 8-anilino- l-naphthalensulfonic acid ammonium salt free in water as a fluorescent probe, the current study reveals that the transition has two distinct stages with two characteristic times, namely, Tfast≈0.1 ms, which can be attributed to the nucleation and formation of some ＂pearls＂ （locally contracting segments） on the chain, and tslow≈0.5 ms, which is related to the merging and coarsening of the ＂pearls＂.Tfast is independent of the PNIPAM chain length over a wide range （Mw=2.8× 10^6-4.2 × 10^7 g/mol）. On the other hand, Tslow only slightly increases with the chain length.
基金supported by the National Natural Science Foundation of China (51502089,51302008)the Fundamental Research Funds for the Central Universities (2016MS03)~~
文摘Ultra‐small metal nanoclusters have high surface energy and abundant active sites,and thereforetheir catalytic activities are usually significantly higher than those of larger nanoparticles.A temperature‐responsive copolymer,namely poly(ethylene glycol)‐co‐poly(N‐isopropylacrylamide)(PEG‐PNIPAM)was synthesized as the first step,and then ultra‐small Pd clusters stabilized withinPEG‐PNIPAM copolymer micelles were formed by direct reduction.Pd nanoclusters of size less than2nm showed outstanding catalytic activity in the Suzuki coupling reaction.The reaction betweeniodobenzene and phenylboronic acid was completed in as little as10s(turnover frequency=4.3×104h?1).A yield of64%was achieved in5min in the reaction between chlorobenzene and phenylboronicacid.The catalyst showed significant deactivation during three consecutive runs.However,this composite catalyst consisting of Pd/PEG‐PNIPAM can be easily recycled based on the reversiblephase transition of temperature‐responsive PEG‐PNIPAM.This catalyst therefore has good potentialfor practical applications.
基金Project(08Y038) supported by Jiangsu Transportation Engineering Construction Bureau,China
文摘The main objective of this work is to propose new mixture response parameters and to compare correlations with rut depths and sensitivity of permanent deformation response parameters based on field extracted cores and lab-mixed duplicates. A new "mix-confined" test is developed and four new parameters for this test are proposed. Correlation coefficients with rut depths and coefficients of variation (sensitivity) are compared between the four new and two existing parameters. Some parameters are recommended to be used for the newly developed test. The results show that, newly developed test can capture the changes of permanent deformation of asphalt mixtures. Only one new parameter (D1 of Stephen Price model) and one existing parameter (flow number, Fn ) have strong correlations with rut depths of asphalt pavements (R2 greater than 0.7) and have relative small sensitivity (coefficient of variation, COV, less than 30%). For polymer modified asphalt mixtures, the parameter D1 rather than Fn should be used. These findings can be used to check the permanent deformation of asphalt mixture during the mix design.
基金supported by the National Natural Science Foundation of China(21274137,51273190,91027026,and 51033005)the Specialized Research Fund for the Doctoral Program of Higher Education(20123402130010)
文摘We report on the fabrication of fluorescent and multicolor probes for Zn^2＋ ions and temperature from a mixture of three types of fluorophore-labeled responsive block copolymers in aqueous media. Quinoline-based Zn^2＋-recognizing fluorescent mono- mer ZQMA, red-emitting rhodamine B-based monomer RhBEA, and blue-emitting coumarin derivative Coum-OH, were syn- thesized first. A ZQMA-labeled well-defined double hydrophilic block copolymer （DHBC）, PEG-b-P（MEO2MA-co-ZQMA）, was synthesized via reversible addition-fragmentation chain-transfer （RAFT） polymerization of 2-（2-methoxyethoxy）ethyl methacrylate （MEOzMA） and ZQMA by utilizing a PEG-based macroRAFT agent. Following similar procedures, PEG-b-P（St-co-RhBEA） amphiphilic diblock copolymer and PEG-b-P（MEOzMA-co-Coum） DHBC were also synthesized, where P（St-co-RhBEA） was a RhBEA-labeled polystyrene （PS） block. At room temperature in aqueous solution, almost non- fluorescent PEG-b-P（MEOzMA-co-ZQMA） can effectively bind Zn2＋ ions, leading to prominent green fluorescence enhance- ment due to the coordination of ZQMA with Zn^2＋ ions. However, by mixing red-emitting PEG-b-P（St-co-RhBEA） and blue-emitting PEG-b-P（MEO2MA-co-Coum） with PEG-b-P（MEO2MA-co-ZQMA） at an appropriate ratio, three color transitions could be observed. In the absence of Zn^2＋ ions, a mixed pink fluorescent originating from Coum and RhBEA was ob- served; upon the addition of a certain amount of Zn^2＋ ions, the green fluorescence enhanced dramatically, leading to a white fluorescence readout. By further increasing the amount of Zn2＋ ions, the green fluorescence further enhanced and overwhelmed the blue and red emissions, leading to a green-dominant mixed-fluorescence emission. In addition, upon increasing the temperature, the fluorescence of Coum decreased considerably due to the fluorescence-resonance energy transfer （FRET） between Coum and ZQMA moieties. In this way, a ratiometric fluorescent thermometer can be constructed.
