A plastic crack model for smectic A liquid crystals under longitudinal shear is suggested. The solution of the screw dislocation in smectic A is the key to the correct result that we obtained by overcoming a longstand...A plastic crack model for smectic A liquid crystals under longitudinal shear is suggested. The solution of the screw dislocation in smectic A is the key to the correct result that we obtained by overcoming a longstanding puzzle. We further use the dislocation pile-up principle and the singular integral equation method to construct the solution of the crack in the phase. From the solution, we can determine the size of the plastic zone at the crack tip and the crack tip opening (tearing) displacement, which are the parameters relevant to the local stability/instability of materials. Our results may be useful for developing soft-matter mechanics.展开更多
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
Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain...Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain. Dielectric relaxation study and electro-optical measurements are carried out with the classical SSFLC geometry. The field-induced phase transitions are studied and the(E,T) phase diagram is established.展开更多
In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the(E, T) phase diagram of the studied pr...In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the(E, T) phase diagram of the studied product can be obtained.In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.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
Amphiphilic molecules adsorbed at the interface could control the orientation of liquid crystals(LCs)while LCs in turn could influence the distributions of amphiphilic molecules.The studies on the interactions between...Amphiphilic molecules adsorbed at the interface could control the orientation of liquid crystals(LCs)while LCs in turn could influence the distributions of amphiphilic molecules.The studies on the interactions between liquid crystals and amphiphilic molecules at the interface are important for the development of molecular sensors.In this paper,we demonstrate that the development of smectic LC ordering from isotropic at the LC/water interface could induce local high-density distributions of amphiphilic phospholipids.Mixtures of liquid crystals and phospholipids in chloroform are first emulsified in water.By fluorescently labeling the phospholipids adsorbed at the interface,their distributions are visualized under fluorescent confocal microscope.Interestingly,local high-density distributions of phospholipids showing a high fluorescent intensity are observed on the surface of LC droplets.Investigations on the correlation between phospholipid density,surface tension and smectic LC ordering suggest that when domains of smectic LC layers nucleate and grow from isotropic at the LC/water interface as chloroform slowly evaporates at room temperature,phospholipids transition from liquid-expanded to liquid-condensed phases in response to the smectic ordering,which induces a higher surface tension at the interface.The results will provide an important insight into the interactions between liquid crystals and amphiphilic molecules at the interface.展开更多
The elec rooptic effect of a smectic A liquid crystal has been investigated by many authors. When an appropriate electric field is applied to the smectic A liquid crystal, the transparent texture is transformed to the...The elec rooptic effect of a smectic A liquid crystal has been investigated by many authors. When an appropriate electric field is applied to the smectic A liquid crystal, the transparent texture is transformed to the scattering texture through the deformation展开更多
5-[(4'-Heptoxy-4-biphenylyl)carbonyloxy]-1-pentyne(A-3,7) was synthesized and the phase structures and transitions were investigated by differential scanning calorimetry(DSC),wide angle X-ray diffraction(WAXD...5-[(4'-Heptoxy-4-biphenylyl)carbonyloxy]-1-pentyne(A-3,7) was synthesized and the phase structures and transitions were investigated by differential scanning calorimetry(DSC),wide angle X-ray diffraction(WAXD),polarized light microscopy(PLM) and the molecular packing in the crystal and liquid crystalline phases were simulated by molecular dynamic simulation.The results showed that the sample formed thermodynamically metastable SmA and SmC_2 phases before crystallized during cooling and the crystal phase directly transformed into isotropic phase during heating.展开更多
The observation of disclination cores of high strength S=-2, -3, -4, -5, -6, -7, -8 in a smectic C phase of Schiff-base type liquid crystal (LC) is reported. The results of polarizing optical microscope (POM), dif-fer...The observation of disclination cores of high strength S=-2, -3, -4, -5, -6, -7, -8 in a smectic C phase of Schiff-base type liquid crystal (LC) is reported. The results of polarizing optical microscope (POM), dif-ferential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) prove that the sample exhibits smectic C phase. It is suggested that the formation of the high strength disclination is mainly ascribed to the stronger anchoring of LC molecules on the substrate due to the formation of hydrogen bonds between the pendent hydroxyl of the LC molecule and the substrate.展开更多
Long-range order crystalline thin films of organic semiconductors have attracted wide attention owing to their high charge carrier mobility.However,uncontrolled crystal nucleation and growth during the thin film dryin...Long-range order crystalline thin films of organic semiconductors have attracted wide attention owing to their high charge carrier mobility.However,uncontrolled crystal nucleation and growth during the thin film drying process cause the formation of grain boundaries,thereby limiting the long-range order.Herein,we achieved the oriented nucleation and growth of organic semiconductors by off-centre spin-coating at the temperature of the smectic E(SmE)liquid crystal mesophase,and then followed by Ostwald ripening during solvent vapour annealing.The thin film of 2-(5-heptylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophne(C7-T-BTBT)blended with 40%(mass fraction)poly(methyl methacrylate)(PMMA)was prepared by off-centrespin-coating at SmE mesophase(170°C),followed by solvent vapour annealing in chloroform for 24 h(chloroform is a good solvent for C7-T-BTBT and PMMA).The C7-T-BTBT molecules grew to rod-like crystals,which were mostly arranged parallel to each other.The crystal growth was perfect and resulted in a single crystal.The average length of the crystals was approximately 87µm.Moreover,the highest charge carrier mobility is 1.62 cm^(2)·V^(−1)·s^(−1) as against that of the film prepared at 25°C(0.06 cm^(2)·V^(−1)·s^(−1)).展开更多
A liquid crystalline carbosilane dendrimer has been synthesized in successive steps, resulting in the formation of defined, unimolecular compound. 12 AZO-meso-units were attached on its periphery and it has a three di...A liquid crystalline carbosilane dendrimer has been synthesized in successive steps, resulting in the formation of defined, unimolecular compound. 12 AZO-meso-units were attached on its periphery and it has a three dimentional, tree-like, starburst structure.Its phase behavior was K64 Sx115 SA123N138I. Compared with its AZO-meso-unit, 4-nitro-4’- (llydroxyhexyl)-azobenzene, whose phase behavior was K122N132I, its phase range was enlarged about 64 ℃ and two more liquid crystalline phases SA Sx were found.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11272055)
文摘A plastic crack model for smectic A liquid crystals under longitudinal shear is suggested. The solution of the screw dislocation in smectic A is the key to the correct result that we obtained by overcoming a longstanding puzzle. We further use the dislocation pile-up principle and the singular integral equation method to construct the solution of the crack in the phase. From the solution, we can determine the size of the plastic zone at the crack tip and the crack tip opening (tearing) displacement, which are the parameters relevant to the local stability/instability of materials. Our results may be useful for developing soft-matter mechanics.
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Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain. Dielectric relaxation study and electro-optical measurements are carried out with the classical SSFLC geometry. The field-induced phase transitions are studied and the(E,T) phase diagram is established.
文摘In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the(E, T) phase diagram of the studied product can be obtained.In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.
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supported by Zhejiang Provincial Natural Science Foundation of China(No.LY20B060027)National Natural Science Foundation of China(No.21878258)+2 种基金the Spanish Ministry of Economy MINECO for a Juan de la Cierva-Incorporacion Fellowship(No.IJCI-2014-22461)supported by the National Science Foundation(No.DMR1310266)the Harvard Materials Research Science and Engineering Center(No.DMR-1420570)。
文摘Amphiphilic molecules adsorbed at the interface could control the orientation of liquid crystals(LCs)while LCs in turn could influence the distributions of amphiphilic molecules.The studies on the interactions between liquid crystals and amphiphilic molecules at the interface are important for the development of molecular sensors.In this paper,we demonstrate that the development of smectic LC ordering from isotropic at the LC/water interface could induce local high-density distributions of amphiphilic phospholipids.Mixtures of liquid crystals and phospholipids in chloroform are first emulsified in water.By fluorescently labeling the phospholipids adsorbed at the interface,their distributions are visualized under fluorescent confocal microscope.Interestingly,local high-density distributions of phospholipids showing a high fluorescent intensity are observed on the surface of LC droplets.Investigations on the correlation between phospholipid density,surface tension and smectic LC ordering suggest that when domains of smectic LC layers nucleate and grow from isotropic at the LC/water interface as chloroform slowly evaporates at room temperature,phospholipids transition from liquid-expanded to liquid-condensed phases in response to the smectic ordering,which induces a higher surface tension at the interface.The results will provide an important insight into the interactions between liquid crystals and amphiphilic molecules at the interface.
文摘The elec rooptic effect of a smectic A liquid crystal has been investigated by many authors. When an appropriate electric field is applied to the smectic A liquid crystal, the transparent texture is transformed to the scattering texture through the deformation
基金the financial supports of National Natural Science Foundation of China (No21074073)Shenzhen Key Laboratory of Functional Polymers(NoFP20100011)
文摘5-[(4'-Heptoxy-4-biphenylyl)carbonyloxy]-1-pentyne(A-3,7) was synthesized and the phase structures and transitions were investigated by differential scanning calorimetry(DSC),wide angle X-ray diffraction(WAXD),polarized light microscopy(PLM) and the molecular packing in the crystal and liquid crystalline phases were simulated by molecular dynamic simulation.The results showed that the sample formed thermodynamically metastable SmA and SmC_2 phases before crystallized during cooling and the crystal phase directly transformed into isotropic phase during heating.
基金the National Natural Science Foundation of China (Nos.29874020, 59573029), the Natural Science Foundation of Shandong Province of China and the Science Foundation of Polymer Physics Laboratory, the Chinese Academy of Sciences.
文摘The observation of disclination cores of high strength S=-2, -3, -4, -5, -6, -7, -8 in a smectic C phase of Schiff-base type liquid crystal (LC) is reported. The results of polarizing optical microscope (POM), dif-ferential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) prove that the sample exhibits smectic C phase. It is suggested that the formation of the high strength disclination is mainly ascribed to the stronger anchoring of LC molecules on the substrate due to the formation of hydrogen bonds between the pendent hydroxyl of the LC molecule and the substrate.
基金supported by the National Natural Science Foundation of China(Nos.51933010,91833306,52003269)the Key Scientific and Technological Innovation Team Project of Shaanxi Province,China(No.2020TD-002).
文摘Long-range order crystalline thin films of organic semiconductors have attracted wide attention owing to their high charge carrier mobility.However,uncontrolled crystal nucleation and growth during the thin film drying process cause the formation of grain boundaries,thereby limiting the long-range order.Herein,we achieved the oriented nucleation and growth of organic semiconductors by off-centre spin-coating at the temperature of the smectic E(SmE)liquid crystal mesophase,and then followed by Ostwald ripening during solvent vapour annealing.The thin film of 2-(5-heptylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophne(C7-T-BTBT)blended with 40%(mass fraction)poly(methyl methacrylate)(PMMA)was prepared by off-centrespin-coating at SmE mesophase(170°C),followed by solvent vapour annealing in chloroform for 24 h(chloroform is a good solvent for C7-T-BTBT and PMMA).The C7-T-BTBT molecules grew to rod-like crystals,which were mostly arranged parallel to each other.The crystal growth was perfect and resulted in a single crystal.The average length of the crystals was approximately 87µm.Moreover,the highest charge carrier mobility is 1.62 cm^(2)·V^(−1)·s^(−1) as against that of the film prepared at 25°C(0.06 cm^(2)·V^(−1)·s^(−1)).
文摘A liquid crystalline carbosilane dendrimer has been synthesized in successive steps, resulting in the formation of defined, unimolecular compound. 12 AZO-meso-units were attached on its periphery and it has a three dimentional, tree-like, starburst structure.Its phase behavior was K64 Sx115 SA123N138I. Compared with its AZO-meso-unit, 4-nitro-4’- (llydroxyhexyl)-azobenzene, whose phase behavior was K122N132I, its phase range was enlarged about 64 ℃ and two more liquid crystalline phases SA Sx were found.