Synthesis of conductive polymer poly([thiophene]-[benzo[1,2,3]thiadiazole] [thiophene]) (abbreviated as P(T-Btdaz-T)) was achieved by electrochemical polymerization in hydroxypropyl cellulose (HPC)/N,N-dimethylformami...Synthesis of conductive polymer poly([thiophene]-[benzo[1,2,3]thiadiazole] [thiophene]) (abbreviated as P(T-Btdaz-T)) was achieved by electrochemical polymerization in hydroxypropyl cellulose (HPC)/N,N-dimethylformamide (DMF) in liquid crystal state. The polymer thus obtained shows fingerprint texture, which is derived from helical structure of the HPC in cholesteric liquid crystal state. Fourier transform infrared spectroscopy measurements revealed that the polymer film is P(T-Btdaz-T)/HPC composite. Circular dichroism optical absorption spectroscopy measurements show that the polymer has the optical activity. Next, electrochemical polymerization of 3,4-ethylene-dioxythiophene (EDOT) was carried out in columnar phase liquid crystal. The polymer transcribes the columnar structure and shows optical structure resembling columnar liquid crystal electrolyte solution.展开更多
This paper applies a phase field model for polycrystalline solidification in binary alloys to simulate the formation and growth of the columnar dendritic array under the isothermal and constant cooling conditions. The...This paper applies a phase field model for polycrystalline solidification in binary alloys to simulate the formation and growth of the columnar dendritic array under the isothermal and constant cooling conditions. The solidification process and microsegregation in the mushy zone are analysed in detail. It is shown that under the isothermal condition solidification will stop after the formation of the mushy zone, but dendritic coarsening will progress continuously, which results in the decrease of the total interface area. Under the constant cooling condition the mushy zone will solidify and coarsen simultaneously. For the constant cooling solidification, microsegregation predicted by a modified Brody- Flemings model is compared with the simulation results. It is found that the Fourier number which characterizes microsegregation is different for regions with different microstructures. Dendritic coarsening and the larger area of interface should account for the enhanced Fourier number in the region with well developed second dendritic arms.展开更多
The phase behaviors and structures of a triphenylene-derived discotic liquid crystal （LC） hexa-n-octoxyl- triphenylene （C8HET） were studied using the combined techniques of differential scanning calorimetry （DSC...The phase behaviors and structures of a triphenylene-derived discotic liquid crystal （LC） hexa-n-octoxyl- triphenylene （C8HET） were studied using the combined techniques of differential scanning calorimetry （DSC）, wide angle X-ray diffraction （WAXD）, selected area electron diffraction （SAED） and polarized light microscopy （PLM）. Onedimensional （1D） powder WAXD results at different temperatures coupled with DSC and PLM observations revealed that the C8HET compound possessed an LC phase and three different crystalline （K3, K2 and K1） phases below the isotropic （I） melt. The I←→ LC phase transition was thermodynamically reversible and independent of the heating and cooling rates. The development and experimental observation of the three crystalline phases relied on different thermal histories. Among the three crystalline phases in CSHET, the K3 phase is the most stable phase, while the K2 and K1 phases are metastable. Note that the K1 phase only formed via a quenching process. Oh the basis of structure sensitive diffraction experiments such as 2D WAXD of oriented samples and SAED of single crystals, detailed structures and molecular packings of these four ordered phases were identified. The LC phase exhibited a hexagonal columnar phase with 2D lattice dimensions ofa = b = 2.38 nm and γ= 120°. All the three crystalline phases possess monoclinic unit cells, yet the y angle is not 90° in the cases of the K2 and the K3 phases, while in the case of the K1 phase the a angle is not 90°.展开更多
Small change in chemical structure of discotic liquid crystals can cause big difference in their mesomorphism. Replacing of the alkoxy peripheral chains of triphenylene by oxygen-atom containing ester chains would res...Small change in chemical structure of discotic liquid crystals can cause big difference in their mesomorphism. Replacing of the alkoxy peripheral chains of triphenylene by oxygen-atom containing ester chains would result in novel mesomorphism. A series of mixed tail triphenylenes containing propoxyacetyloxy and alkoxy, abbreviated as C18H6（OCnH2n＋1）3（OCOCH2OC3H7）3, n=4-8, and hexa（propyloxyacetyloxy）triphenylene, C18H6（OCOCH2OC3H7）6 were synthesized. Thermal gravimetry analysis （TGA） of three discogens showed that they had good thermal stability till 350 ℃. The mesomorphism was investigated through differential scanning calorimetry （DSC） and polarized optical microscopy （POM）. The preliminary X-ray diffraction （XRD） results of one compound showed that it exhibited ordered hexagonal columnar （Colho） mesophase. These mixed tail triphenylene derivatives possessed much stable Colho mesophase and wider mesophase ranges than their hexaalkoxytriphenylene C18H6（OR）6 and hexaalkanoyloxytriphenylene C18H6（OCOR＇）6 analogues. The asymmetrical compounds 2,6,11-trialkoxy-3,7,10-tri（2-propyloxyacetyloxy）triphenylenes with n=5-8 displayed higher clearing points and wider temperature ranges than their symmetrical isomers 2,6,10-trialkoxy-3,7,11-tri（2-propyloxyacetyloxy）- triphenylenes, while C18H6（OCOCH2OC3H7）6 had the highest clearing point due to the β-oxygen-atom effect.展开更多
A series of side chain liquid crystalline polymers （SCLCPs） containing triphenylene （Tp） units in the side chains, denoted as PMTS （without spacer） and PMTnS （n = 2, 3, 4, 6, which is the number of the methylen...A series of side chain liquid crystalline polymers （SCLCPs） containing triphenylene （Tp） units in the side chains, denoted as PMTS （without spacer） and PMTnS （n = 2, 3, 4, 6, which is the number of the methylene units between the main chain and Tp moieties in the side chains）, with different lengths of spacers were synthesized through conventional free radical polymerization. The chemical structures of the monomers were confirmed by 1H/IaC-NMR, and the phase behaviors were examined by differential scanning calorimetry （DSC）, polarized optical microscopy （POM） and wide-angle X-ray diffraction （1D and 2D WAXD）. The molecular characterization of the polymers was performed with 1H-NMR, gel permeation chromatography （GPC） and thermogravimetric analysis （TGA）. The phase behaviors of the polymers have been investigated by a combination of techniques including DSC, POM, 1D and 2D WAXD. The results showed that the length of spacer has significant effects on the LC phase behavior of polymers. For PMTS and PMT2S, they displayed the columnar phase developed by the Tp moieties and the main chain as a whole due to the strong coupling effect of the Tp moieties and the main chain. For the PMT3S, PMT4S and PMT6S, they formed the symmetry hexagonal columnar （~n） phase owing to the decoupling effect. All of these indicated that the ＂decoupling effect＂ or ＂coupling effect＂ depended on the length of spacers, leading to the different LC phase formation mechanism.展开更多
文摘Synthesis of conductive polymer poly([thiophene]-[benzo[1,2,3]thiadiazole] [thiophene]) (abbreviated as P(T-Btdaz-T)) was achieved by electrochemical polymerization in hydroxypropyl cellulose (HPC)/N,N-dimethylformamide (DMF) in liquid crystal state. The polymer thus obtained shows fingerprint texture, which is derived from helical structure of the HPC in cholesteric liquid crystal state. Fourier transform infrared spectroscopy measurements revealed that the polymer film is P(T-Btdaz-T)/HPC composite. Circular dichroism optical absorption spectroscopy measurements show that the polymer has the optical activity. Next, electrochemical polymerization of 3,4-ethylene-dioxythiophene (EDOT) was carried out in columnar phase liquid crystal. The polymer transcribes the columnar structure and shows optical structure resembling columnar liquid crystal electrolyte solution.
基金supported by the National Natural Science Foundation of China (Grant No 50401013)Doctorate Foundation of Northwestern Polytechnical University,China
文摘This paper applies a phase field model for polycrystalline solidification in binary alloys to simulate the formation and growth of the columnar dendritic array under the isothermal and constant cooling conditions. The solidification process and microsegregation in the mushy zone are analysed in detail. It is shown that under the isothermal condition solidification will stop after the formation of the mushy zone, but dendritic coarsening will progress continuously, which results in the decrease of the total interface area. Under the constant cooling condition the mushy zone will solidify and coarsen simultaneously. For the constant cooling solidification, microsegregation predicted by a modified Brody- Flemings model is compared with the simulation results. It is found that the Fourier number which characterizes microsegregation is different for regions with different microstructures. Dendritic coarsening and the larger area of interface should account for the enhanced Fourier number in the region with well developed second dendritic arms.
基金This work was supported by National Science Foundation of USA (DMR-0516602). The 1D X-ray diffraction research was carried out at the National Synchrotron Light Source in Brookhaven National Laboratory supported by the Department of Energy.
文摘The phase behaviors and structures of a triphenylene-derived discotic liquid crystal （LC） hexa-n-octoxyl- triphenylene （C8HET） were studied using the combined techniques of differential scanning calorimetry （DSC）, wide angle X-ray diffraction （WAXD）, selected area electron diffraction （SAED） and polarized light microscopy （PLM）. Onedimensional （1D） powder WAXD results at different temperatures coupled with DSC and PLM observations revealed that the C8HET compound possessed an LC phase and three different crystalline （K3, K2 and K1） phases below the isotropic （I） melt. The I←→ LC phase transition was thermodynamically reversible and independent of the heating and cooling rates. The development and experimental observation of the three crystalline phases relied on different thermal histories. Among the three crystalline phases in CSHET, the K3 phase is the most stable phase, while the K2 and K1 phases are metastable. Note that the K1 phase only formed via a quenching process. Oh the basis of structure sensitive diffraction experiments such as 2D WAXD of oriented samples and SAED of single crystals, detailed structures and molecular packings of these four ordered phases were identified. The LC phase exhibited a hexagonal columnar phase with 2D lattice dimensions ofa = b = 2.38 nm and γ= 120°. All the three crystalline phases possess monoclinic unit cells, yet the y angle is not 90° in the cases of the K2 and the K3 phases, while in the case of the K1 phase the a angle is not 90°.
基金Project supported by the National Natural Science Foundation of China （Nos. 50473062, 50673069）, the Sichuan Province Youth Foundation （No. 04-ZQ026-044） and the Research Project of Sichuan Province （No. 05GG009-005）, China.
文摘Small change in chemical structure of discotic liquid crystals can cause big difference in their mesomorphism. Replacing of the alkoxy peripheral chains of triphenylene by oxygen-atom containing ester chains would result in novel mesomorphism. A series of mixed tail triphenylenes containing propoxyacetyloxy and alkoxy, abbreviated as C18H6（OCnH2n＋1）3（OCOCH2OC3H7）3, n=4-8, and hexa（propyloxyacetyloxy）triphenylene, C18H6（OCOCH2OC3H7）6 were synthesized. Thermal gravimetry analysis （TGA） of three discogens showed that they had good thermal stability till 350 ℃. The mesomorphism was investigated through differential scanning calorimetry （DSC） and polarized optical microscopy （POM）. The preliminary X-ray diffraction （XRD） results of one compound showed that it exhibited ordered hexagonal columnar （Colho） mesophase. These mixed tail triphenylene derivatives possessed much stable Colho mesophase and wider mesophase ranges than their hexaalkoxytriphenylene C18H6（OR）6 and hexaalkanoyloxytriphenylene C18H6（OCOR＇）6 analogues. The asymmetrical compounds 2,6,11-trialkoxy-3,7,10-tri（2-propyloxyacetyloxy）triphenylenes with n=5-8 displayed higher clearing points and wider temperature ranges than their symmetrical isomers 2,6,10-trialkoxy-3,7,11-tri（2-propyloxyacetyloxy）- triphenylenes, while C18H6（OCOCH2OC3H7）6 had the highest clearing point due to the β-oxygen-atom effect.
基金Supported by National Natural Science Foundation of China(51161003,51561031)Natural Science Foundation of Guangxi Province of China(2015GXNSFBA139240)+1 种基金Scientific Research Foundation of Higher Education Institutions of Guangxi Province of China(YB2014318)Open Foundation of Guangxi Colleges and Universities Key Laboratory of Complex System Optimization and Large Data Processing(2016CSOBDP0101)
基金financially supported by the National Natural Science Foundation of China(No.51373148)the Innovation Platform Open Foundation of University of Hunan Province(No.CX2013B265)
文摘A series of side chain liquid crystalline polymers （SCLCPs） containing triphenylene （Tp） units in the side chains, denoted as PMTS （without spacer） and PMTnS （n = 2, 3, 4, 6, which is the number of the methylene units between the main chain and Tp moieties in the side chains）, with different lengths of spacers were synthesized through conventional free radical polymerization. The chemical structures of the monomers were confirmed by 1H/IaC-NMR, and the phase behaviors were examined by differential scanning calorimetry （DSC）, polarized optical microscopy （POM） and wide-angle X-ray diffraction （1D and 2D WAXD）. The molecular characterization of the polymers was performed with 1H-NMR, gel permeation chromatography （GPC） and thermogravimetric analysis （TGA）. The phase behaviors of the polymers have been investigated by a combination of techniques including DSC, POM, 1D and 2D WAXD. The results showed that the length of spacer has significant effects on the LC phase behavior of polymers. For PMTS and PMT2S, they displayed the columnar phase developed by the Tp moieties and the main chain as a whole due to the strong coupling effect of the Tp moieties and the main chain. For the PMT3S, PMT4S and PMT6S, they formed the symmetry hexagonal columnar （~n） phase owing to the decoupling effect. All of these indicated that the ＂decoupling effect＂ or ＂coupling effect＂ depended on the length of spacers, leading to the different LC phase formation mechanism.
