A new series of chiral shish-kebab type liquid crystal block copolymers that form the smectic C(Sc*) phase was synthesized by solution polycondensation. The copolymers were characterized by GPC, DSC, TG, POM, X-ray di...A new series of chiral shish-kebab type liquid crystal block copolymers that form the smectic C(Sc*) phase was synthesized by solution polycondensation. The copolymers were characterized by GPC, DSC, TG, POM, X-ray diffraction and polarimeter. The copolymers 7 entered into liquid crystal phase whin they were heated to their melting temperatures (T-m) and the copolymers 8 were in liquid crystal phase at room temperature with low viscosities. The smectic sanded texture or focal-conic texture were observed on POM. All the chiral block copolymers showed high optical activity. No racemization has happened. Temperature-variable X-ray diffraction study together with POM and polarimetric analysis realized that they are chiral smectic C(Sc*) phase. Thus we offer in this report the first example of shish-kebab type liquid crystal block copolymers that form a chiral smectic C(Sc*) phase. The variation of melting and isotropization temperatures with molecular structure was also discussed.展开更多
Dielectric relaxation and spontaneous polarization studies have been carried out in a low molar mass organosiloxane liquid crystal, TSi10PPBN4 which displays a wide temperature range of de Vries Smectic A* and chiral ...Dielectric relaxation and spontaneous polarization studies have been carried out in a low molar mass organosiloxane liquid crystal, TSi10PPBN4 which displays a wide temperature range of de Vries Smectic A* and chiral Smectic C* phases. The temperature variation of the permittivity and dielectric loss studied are found to have anomalous variations in the vicinity of the phase transitions. The frequency variation of permittivity and dielectric loss are also studied in the de Vries Smectic A* and Smectic C* phases. The relaxation frequency, fR is found to decrease with decreasing temperature. Temperature variation of fR is found to follow an Arrhenius shift from which the activation energy is estimated. The thermal variation of the spontaneous polarization, Ps is measured using the polarization reversal technique in the Smectic C* phase. Ps increases initially, reaches a peak value and then drops drastically in the vicinity of the SmC*-SmA*de Vries phase transition.展开更多
A homologous series of benzothiazole derivatives, 6-methoxy-2-（4-alkanoyloxybenzylidenamino）benzothiazoles, were synthesized and characterized using FT-IR, ^1H and ^13C NMR, mass spectrometry and elemental analysis....A homologous series of benzothiazole derivatives, 6-methoxy-2-（4-alkanoyloxybenzylidenamino）benzothiazoles, were synthesized and characterized using FT-IR, ^1H and ^13C NMR, mass spectrometry and elemental analysis. Enantiotropic nematic phase was observed throughout the entire series. Smectic C phase only emerged from the decanoyloxy derivative onwards. The terminal methoxyl group and the ester linkage influenced the mesomorphic behavior of the present series.展开更多
In this paper, the synthesis of new mesomorphic benzothiazolyl derivatives, 6-ethoxy-2-[4-（4- alkyloxybenzoyloxy）benzylidenamino]benzothiazoles, is presented. The structures of the title compounds were elucidated us...In this paper, the synthesis of new mesomorphic benzothiazolyl derivatives, 6-ethoxy-2-[4-（4- alkyloxybenzoyloxy）benzylidenamino]benzothiazoles, is presented. The structures of the title compounds were elucidated using spectroscopic techniques, such as FT-IR, NMR （1H and 13C）, elemental analysis and El-MS. The mesomorphic behaviours of these compounds were determined by differential scanning calorimetric and polarizing optical microscopic techniques. Compounds exhibited nematic and tilted smectic phases upon heating from crystal phase. An obvious odd-even effect was observed in this homologous series.展开更多
In this investigation,the dielectric behaviors of three ferroelectric liquid crystals(FLCs)belonging to a homologous series have been revealed in the frequency range of 10 Hz-10 MHz.FLCs used in this study are three-r...In this investigation,the dielectric behaviors of three ferroelectric liquid crystals(FLCs)belonging to a homologous series have been revealed in the frequency range of 10 Hz-10 MHz.FLCs used in this study are three-ring calamitic LCs,namely(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-octyloxy)benzoate,(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-decyloxy)benzoate and(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-undecyloxy)benzoate.The polarizing optical microscopic and differential scanning calorimetric results confirm that these compounds,synthesized as per the known synthetic steps,show not only a ferroelectrically switchable chiral smectic C(SmC*)phase over a wide thermal range,but also other mesophases such as blue phase-I/II(BP-I/II),chiral nematic(N*)and unknown smectic(SmX)phases.Several essential dielectric parameters of the FLC phase have been measured at different temperatures.The relative permittivity has been measured with the variations of temperature and frequency.Besides,the dielectric loss and tanδhave been measured.Different dielectric relaxations have been calculated and explained at the molecular level.The systematic measurements revealed a strong anomaly,and crossover of relative permittivity values for the FLCs has been determined at selective frequencies between 1 kHz and 20 kHz.Strong dielectric anomaly/fall for the response function infers the involvement of collective response of dipolar assembly confined to ferroelectric Weiss domains.展开更多
基金This work was supported by the National Natural Science Foundation of China (No. 29674025) and the Natural Science Foundation of Henan Province.
文摘A new series of chiral shish-kebab type liquid crystal block copolymers that form the smectic C(Sc*) phase was synthesized by solution polycondensation. The copolymers were characterized by GPC, DSC, TG, POM, X-ray diffraction and polarimeter. The copolymers 7 entered into liquid crystal phase whin they were heated to their melting temperatures (T-m) and the copolymers 8 were in liquid crystal phase at room temperature with low viscosities. The smectic sanded texture or focal-conic texture were observed on POM. All the chiral block copolymers showed high optical activity. No racemization has happened. Temperature-variable X-ray diffraction study together with POM and polarimetric analysis realized that they are chiral smectic C(Sc*) phase. Thus we offer in this report the first example of shish-kebab type liquid crystal block copolymers that form a chiral smectic C(Sc*) phase. The variation of melting and isotropization temperatures with molecular structure was also discussed.
文摘Dielectric relaxation and spontaneous polarization studies have been carried out in a low molar mass organosiloxane liquid crystal, TSi10PPBN4 which displays a wide temperature range of de Vries Smectic A* and chiral Smectic C* phases. The temperature variation of the permittivity and dielectric loss studied are found to have anomalous variations in the vicinity of the phase transitions. The frequency variation of permittivity and dielectric loss are also studied in the de Vries Smectic A* and Smectic C* phases. The relaxation frequency, fR is found to decrease with decreasing temperature. Temperature variation of fR is found to follow an Arrhenius shift from which the activation energy is estimated. The thermal variation of the spontaneous polarization, Ps is measured using the polarization reversal technique in the Smectic C* phase. Ps increases initially, reaches a peak value and then drops drastically in the vicinity of the SmC*-SmA*de Vries phase transition.
基金Universiti Tunku Abdul Rahrnan(UTAR) for the research facilities and financial support(No.6202/K06)the Malaysian Toray Science Foundation(No.4359/000) for funding this project.T.M.Koh would like to acknowledge UTAR for the award of the research and teaching assistantships.
文摘A homologous series of benzothiazole derivatives, 6-methoxy-2-（4-alkanoyloxybenzylidenamino）benzothiazoles, were synthesized and characterized using FT-IR, ^1H and ^13C NMR, mass spectrometry and elemental analysis. Enantiotropic nematic phase was observed throughout the entire series. Smectic C phase only emerged from the decanoyloxy derivative onwards. The terminal methoxyl group and the ester linkage influenced the mesomorphic behavior of the present series.
基金Universiti Tunku Abdul Rahman for the fnancial supports and research facilities
文摘In this paper, the synthesis of new mesomorphic benzothiazolyl derivatives, 6-ethoxy-2-[4-（4- alkyloxybenzoyloxy）benzylidenamino]benzothiazoles, is presented. The structures of the title compounds were elucidated using spectroscopic techniques, such as FT-IR, NMR （1H and 13C）, elemental analysis and El-MS. The mesomorphic behaviours of these compounds were determined by differential scanning calorimetric and polarizing optical microscopic techniques. Compounds exhibited nematic and tilted smectic phases upon heating from crystal phase. An obvious odd-even effect was observed in this homologous series.
文摘In this investigation,the dielectric behaviors of three ferroelectric liquid crystals(FLCs)belonging to a homologous series have been revealed in the frequency range of 10 Hz-10 MHz.FLCs used in this study are three-ring calamitic LCs,namely(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-octyloxy)benzoate,(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-decyloxy)benzoate and(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-undecyloxy)benzoate.The polarizing optical microscopic and differential scanning calorimetric results confirm that these compounds,synthesized as per the known synthetic steps,show not only a ferroelectrically switchable chiral smectic C(SmC*)phase over a wide thermal range,but also other mesophases such as blue phase-I/II(BP-I/II),chiral nematic(N*)and unknown smectic(SmX)phases.Several essential dielectric parameters of the FLC phase have been measured at different temperatures.The relative permittivity has been measured with the variations of temperature and frequency.Besides,the dielectric loss and tanδhave been measured.Different dielectric relaxations have been calculated and explained at the molecular level.The systematic measurements revealed a strong anomaly,and crossover of relative permittivity values for the FLCs has been determined at selective frequencies between 1 kHz and 20 kHz.Strong dielectric anomaly/fall for the response function infers the involvement of collective response of dipolar assembly confined to ferroelectric Weiss domains.
