In this paper, we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer tem- plated blue phase liquid crystal grating. This grating is obtained by preforming a polymer template...In this paper, we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer tem- plated blue phase liquid crystal grating. This grating is obtained by preforming a polymer template comprised of periodic fringes, and then refilling it with a blue phase liquid crystal. Compared with conventional holographic polymer dispersed liquid crystal gratings, our grating can remarkably reduce its switching voltage from 200 V to 43 V while maintaining a sub-millisecond response time. The holographic polymer templated blue phase liquid crystal (HPTBPLC) grating is free from electrode patterning, thus leading to a lower cost and more flexible applications.展开更多
The study of phase transition processes in liquid crystals(LCs)remains challenging.Most thermotropic LCs exhibit a narrow temperature range and a rapid phase transition from the isotropic(ISO)to the nematic(N)phase,wh...The study of phase transition processes in liquid crystals(LCs)remains challenging.Most thermotropic LCs exhibit a narrow temperature range and a rapid phase transition from the isotropic(ISO)to the nematic(N)phase,which make it difficult to capture and manipulate the phase transition process.In this study,we observed the evolution of small droplets during the ISO–N phase transition in ferroelectric nematic(NF)LC RM734.After doping with metal nanoparticles(NPs),the temperature range of the phase transition broadened,and the droplets formed during the phase transition remained stable,with their diameter increasing linearly with temperature.In addition,droplets doped with NPs can be well controlled by an external electric field.This discovery not only aids in understanding the fundamental mechanisms of LC phase transitions but also provides a simple alternative method for preparing droplets,which is potentially valuable for applications in optoelectronic devices and sensors.展开更多
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
2-Hydroxyethyl methacrylate (HEMA) and styrene copolymers are prepared by photopolymerization. The electrooptical behavior and microstructure of the polymer dispersed liquid crystal films are investigated by using He-...2-Hydroxyethyl methacrylate (HEMA) and styrene copolymers are prepared by photopolymerization. The electrooptical behavior and microstructure of the polymer dispersed liquid crystal films are investigated by using He-Ne laser and scanning electron microscopy, respectively. With increasing E7 content in the copolymer, droplet size increased, threshold voltage decreased.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
Lanthanide-containing liquid crystals exhibiting smectic A phase close to room temperature were obtained. Photoacoustic (PA) spectroscopy was used to study the spectral properties and phase transitions of liquid cry...Lanthanide-containing liquid crystals exhibiting smectic A phase close to room temperature were obtained. Photoacoustic (PA) spectroscopy was used to study the spectral properties and phase transitions of liquid crystalline metal complexes. It was found that PA intensity of the ligand had a relationship with the probability of nonradiative transitions, which increased in the order of Eu(tta)3L2〈La(tta)3L2〈 Tb(tta)3L2〈Er(tta)3L2. The relaxation processes of the complexes were studied in depth from two aspects: radiative and non-radiative processes, combining with their fluorescence spectra. Phase transitions of europium(m) and erbium(m) complexes, in the temperature range of 383-358 K, could be clearly monitored by both PA amplitude and PA phase signals. As the temperature crossed the transition point, PA amplitude showed a minimum and PA phase a maximum. The results indicated that PA technique could serve as a new tool for investigating the physicochemical properties of liquid crystals containing metal ions.展开更多
Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to estab...Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to establish the multiplicity of dielectric relaxationtransitions which reflects the small- and large-scale types of molecular motion. It was shownthat dielectric relaxation processes occurring in accordance with local mechanism (relaxationtimes 10^(-9)--10^(-7)s. and the activation energy 10--50kJ/mol) are due to the mobility of kineticchain elements of different length within a monomer units. It was found that the dielectricrelaxation process connected with a large-scale form of molecular motion (relaxation times10^(-5)--10^(-6)s. and the activation energy 100kJ/mol) did not depend on the molecular massbut was infiuenced by factors changing the conformational state of the macromolecule. It isestablished tha the cooperative reorientation mobility of associated mesogenic fragments isthe source of the large-scale process.展开更多
A new type of liquid crystalline polyesters with resorcin as one part of the mesogenic unitconnected together by polymethylene, or phenylene group, and lateral groups consisting of arigid azobenzene as another part of...A new type of liquid crystalline polyesters with resorcin as one part of the mesogenic unitconnected together by polymethylene, or phenylene group, and lateral groups consisting of arigid azobenzene as another part of the mesogenic unit were synthesized by interfacialpolymerization of diacyl chlorides in 1, 2-dichloroethane and 2, 4-dihydroxy-4'-nitroazobenzen inaqueous alkaline solution. The polyester structures were confirmed by proton NMR and IRspectra. Their phase transition behavior and texture were studied by polarizing microscopy andDSC.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
A series of poly{2,5-bis[(4-butoxyphenyl)-oxycarbonyl]styrenes}(PBPCS)with low mo-lecular weight distribution was synthesized by atom transfer radical polymerization(ATRP).The me-somorphic properties were investigated...A series of poly{2,5-bis[(4-butoxyphenyl)-oxycarbonyl]styrenes}(PBPCS)with low mo-lecular weight distribution was synthesized by atom transfer radical polymerization(ATRP).The me-somorphic properties were investigated by differential scanning calorimetry(DSC),polarizing optical microscopy(POM)and rheometer.PBPCS showed the phase transition from isotropic into liquid crystal(LC)phase,and the LC phase formed at high temperature and disappeared in the subsequent cooling procedure.Using the WAXD fiber pattern,the phase structure of the PBPCS at higher tem-perature showed hexagonal columnar nematic phase.Experimental results demonstrated that the driving force of the entropy is an important factor during the unusual LC phase formation of PBPCS.展开更多
The present paper covers the phase behavior of poly(pbenzamide)(PBA)/Nylon 6/H 2SO 4 and poly(pphenylene terephthalamide) (PPTA)/Nylon 6/H 2SO 4 systems. The transition temperatures detected by the Depolarized L...The present paper covers the phase behavior of poly(pbenzamide)(PBA)/Nylon 6/H 2SO 4 and poly(pphenylene terephthalamide) (PPTA)/Nylon 6/H 2SO 4 systems. The transition temperatures detected by the Depolarized Light Intensity measurements were used to construct the phase diagram in which the influence of temperature was shown. The enhanced depolarized light intensity observed in the ternary system suggests that the coil polymer chains may tend to be extended and contribute to the overall anisotropy of the liquid crystal phase.展开更多
Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place ov...Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place over the entire temperature range between its meltingpoint and clearing point and the orientation level is strongly temperature-dependent, thedevelopment with time of the magnetic orieatation follows an exponeotial-type relation,and the smectic phase state influences the thermal relaxation process in the absence of themagnetic field.展开更多
Photochromism is the reversible structural change of the molecules upon light irradiation having different spectral pattern before and after irradiation. Liquid crystal (LC) is a long-range orientational order of the ...Photochromism is the reversible structural change of the molecules upon light irradiation having different spectral pattern before and after irradiation. Liquid crystal (LC) is a long-range orientational order of the molecules in between solid and isotropic liquid phases which share the properties of the crystal and liquid phases. 1-Alkyl-2-(ary-lazo)imidazoles, (Raai-CnH2n+1, R = H, Me and n = 10, 12, 14, 16, 18, 20, 22) exhibits photochromism and two of them (Haai-C18H37 and Haai-C22H45) show Liquid crystal (LC) properties. One of these compounds, Meaai-C16H33 is structurally characterized by single crystal X-ray diffraction study. The compounds upon irradiation with UV light show E-to-Z isomerisation. Quantum yields (φE→Z) of E-to-Z isomerisation vary with the molar mass of the compounds. The reverse transformation, Z-to-E, is recorded in thermal condition. The activation energy (Ea) of isomerisation is determined by the controlled temperature reaction. Liquid crystal property of the molecules is examined by polarizing optical microscopy (POM) and DSC. The carbon chain length n = 18 shows nematic (N)-isotropic (I) phase transition and an unknown Smectic (Sm) phase is observed with n = 22 on heating cycle.展开更多
Various characteristics of mesomorphism can be explained using intermolecular interactions between a pair of liquid crystalline molecules. The intermolecular interactions have been calculated considering multipole-mul...Various characteristics of mesomorphism can be explained using intermolecular interactions between a pair of liquid crystalline molecules. The intermolecular interactions have been calculated considering multipole-multicentere expansion method and modified by second order perturbation treatments. For calculation of multipole i.e. charge, dipole, etc. at each atomic center of molecules, para-butyl-p’-cyano-biphenyl, GAMESS, an ab initio program, with 6-31G* basis set has been used. The stacking, in-plane and terminal interaction energies explain the liquid crystalline behaviour of the system.展开更多
In this paper,we study the isotropic-nematic phase transition for the nematic liquid crystal based on the Landau-de GennesQ-tensor theory.We justify the limit from the Landau-de Gennes flow to a sharp interface model...In this paper,we study the isotropic-nematic phase transition for the nematic liquid crystal based on the Landau-de GennesQ-tensor theory.We justify the limit from the Landau-de Gennes flow to a sharp interface model:in the isotropic region,Q≡0;in the nematic region,theQ-tensor is constrained on the manifolds={s_(+)(n−1/3I),n∈S^(2)}with s_(+) positive constant,and the evolution of alignment vector fieldobeys the harmonic map heat flow,while the interface separating the isotropic and nematic regions evolves by the mean curvature flow.This problem can be viewed as a concrete but representative case of the Rubinstein-Sternberg-Keller problem introduced in Rubinstein et al.(SIAM J.Appl.Math.49:116-133,1989;SIAM J.Appl.Math.49:1722-1733,1989).展开更多
In this work, the mesophase properties were tuned via mixing two discotic molecules with structural complementarity. Compared with the liquid crystalline hexakis(n-hexyloxy)triphenylene(H6TP)materials(columnar he...In this work, the mesophase properties were tuned via mixing two discotic molecules with structural complementarity. Compared with the liquid crystalline hexakis(n-hexyloxy)triphenylene(H6TP)materials(columnar hexagonal phase from 53 ℃ to 91 ℃), mesophase types as well as phase transition temperatures varied with the introduction of crystalline hexaazatriphenylene derivative(PBH)molecules. The introduction of less than 33% amount of PBH disrupted the columnar hexagonal phase formed by H6 TP remarkably, followed by the decreased clearing temperatures of liquid crystals. As the PBH amount was further increased, the destroyed columnar hexagonal phase was turned into the columnar rectangular phase, in which H6 TP and PBH molecules together formed the columnar mesophase. The formation of new mesophase contributed to the enlarged mesophase temperature(from44 ℃ to 144 ℃). We speculated that the alkyl chains interaction induced by the PBH component competed with the strong p–p stacking between H6 TP molecules, thus altering the liquid crystalline properties including mesophase types and phase transition temperatures.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 synthesis and characterization of novel Schiff base liquid crystalline crown ethers prepared from the inter-mediates 4-(4-alkoxylbiphenyl-4-carbonyl)benzaldehyde, cis- and trans-4,4-diaminodibenzo-18-crown-6 are d...The synthesis and characterization of novel Schiff base liquid crystalline crown ethers prepared from the inter-mediates 4-(4-alkoxylbiphenyl-4-carbonyl)benzaldehyde, cis- and trans-4,4-diaminodibenzo-18-crown-6 are de-scribed. The structure of these compounds have been well characterized by elemental analysis, IR, 1H NMR and MS spectroscopy. The liquid-crystalline behavior of these compounds was also inverstigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) with a heating stage and polarimetric analysis.展开更多
Molecular motions of the luminescent liquid crystals(LLCs)show a significant effect on fluorescent emission and heat generation.In this article,a series of cyanostilbene-based LLCs(CSs:CS1-6,CS1-12,CS2-6 and CS2-12)ar...Molecular motions of the luminescent liquid crystals(LLCs)show a significant effect on fluorescent emission and heat generation.In this article,a series of cyanostilbene-based LLCs(CSs:CS1-6,CS1-12,CS2-6 and CS2-12)are synthesized to investigate how the pho-toluminescence and photothermal effect balanced.Among these materials,the mesogens peripheried by single alkyl chains formed enantiotropic nematic(CS1-6)or smectic C(CS1-12)phase with different alkyl tail lengths.When the single aliphatic chain is re-placed by mini-dendrons,room temperature(RT)monotropic hexagonal columnar phase(CS2-12)or molecular liquid(CS2-6)is formed.The results revealed that all these materials exhibited high efficiency emission with the highest quantum yield reaching 59.0%.The photoluminescence and photothermal effect can be effectively tuned by dispersing CSs into a commercially available RT liquid crystal matrix 8CB,which output significantly improved photothermal conversion efficiency of 63.2%.Furthermore,the pho-tothermal can rapidly trigger the Smectic A-Nematic-Isotropic sequence transitions of 8CB doped with CSs.This work paves a way of adjusting the balance of photoluminescence and photothermal properties of the LLC materials.展开更多
A series of novel tolane-type liquid crystals with amide group as terminal group have been prepared. The terminal amide groups were modified, and the influence of these structural parameters on liquid crystal phases w...A series of novel tolane-type liquid crystals with amide group as terminal group have been prepared. The terminal amide groups were modified, and the influence of these structural parameters on liquid crystal phases was investigated by polarizing optical microscope (POM) and differential scanning calorimetry (DSC). Three of these new compounds exhibit nematic phase, good thermal stabilities. In general, these liquid crystals with amide as end groups have high melting points and phase transition temperatures, which result from the hydrogen bonds. Based on theoretical calculations, these new molecules with strong electron donating amide as end group have narrower HOMO-LUMO energy gap and higher dipole moment than tolane.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2013CB328804)the National Natural Science Foundation of China(Grant No.61307028)+1 种基金the Funds from the Science and Technology Commission of Shanghai Municipality(Grant Nos.11JC1405300,13ZR1420000,and14ZR1422300)the Fundamental Research Funds for the Central Universities,China(Grant No.XDJK 2011C047)
文摘In this paper, we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer tem- plated blue phase liquid crystal grating. This grating is obtained by preforming a polymer template comprised of periodic fringes, and then refilling it with a blue phase liquid crystal. Compared with conventional holographic polymer dispersed liquid crystal gratings, our grating can remarkably reduce its switching voltage from 200 V to 43 V while maintaining a sub-millisecond response time. The holographic polymer templated blue phase liquid crystal (HPTBPLC) grating is free from electrode patterning, thus leading to a lower cost and more flexible applications.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1405000)the Natural Science Foundation of Jiangsu Province(Grant No.BK20211277)+2 种基金the Frontier Leading Technology Basic Research Project of Jiangsu Province(Grant No.BK20212004)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX230971)the Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant No.NY223087).
文摘The study of phase transition processes in liquid crystals(LCs)remains challenging.Most thermotropic LCs exhibit a narrow temperature range and a rapid phase transition from the isotropic(ISO)to the nematic(N)phase,which make it difficult to capture and manipulate the phase transition process.In this study,we observed the evolution of small droplets during the ISO–N phase transition in ferroelectric nematic(NF)LC RM734.After doping with metal nanoparticles(NPs),the temperature range of the phase transition broadened,and the droplets formed during the phase transition remained stable,with their diameter increasing linearly with temperature.In addition,droplets doped with NPs can be well controlled by an external electric field.This discovery not only aids in understanding the fundamental mechanisms of LC phase transitions but also provides a simple alternative method for preparing droplets,which is potentially valuable for applications in optoelectronic devices and sensors.
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.
文摘2-Hydroxyethyl methacrylate (HEMA) and styrene copolymers are prepared by photopolymerization. The electrooptical behavior and microstructure of the polymer dispersed liquid crystal films are investigated by using He-Ne laser and scanning electron microscopy, respectively. With increasing E7 content in the copolymer, droplet size increased, threshold voltage decreased.
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the National Natural Science Foundation of China (10574073, 10574071)
文摘Lanthanide-containing liquid crystals exhibiting smectic A phase close to room temperature were obtained. Photoacoustic (PA) spectroscopy was used to study the spectral properties and phase transitions of liquid crystalline metal complexes. It was found that PA intensity of the ligand had a relationship with the probability of nonradiative transitions, which increased in the order of Eu(tta)3L2〈La(tta)3L2〈 Tb(tta)3L2〈Er(tta)3L2. The relaxation processes of the complexes were studied in depth from two aspects: radiative and non-radiative processes, combining with their fluorescence spectra. Phase transitions of europium(m) and erbium(m) complexes, in the temperature range of 383-358 K, could be clearly monitored by both PA amplitude and PA phase signals. As the temperature crossed the transition point, PA amplitude showed a minimum and PA phase a maximum. The results indicated that PA technique could serve as a new tool for investigating the physicochemical properties of liquid crystals containing metal ions.
文摘Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to establish the multiplicity of dielectric relaxationtransitions which reflects the small- and large-scale types of molecular motion. It was shownthat dielectric relaxation processes occurring in accordance with local mechanism (relaxationtimes 10^(-9)--10^(-7)s. and the activation energy 10--50kJ/mol) are due to the mobility of kineticchain elements of different length within a monomer units. It was found that the dielectricrelaxation process connected with a large-scale form of molecular motion (relaxation times10^(-5)--10^(-6)s. and the activation energy 100kJ/mol) did not depend on the molecular massbut was infiuenced by factors changing the conformational state of the macromolecule. It isestablished tha the cooperative reorientation mobility of associated mesogenic fragments isthe source of the large-scale process.
基金This work is supported by the Structure Research Laboratory,University of Science and Technology of China
文摘A new type of liquid crystalline polyesters with resorcin as one part of the mesogenic unitconnected together by polymethylene, or phenylene group, and lateral groups consisting of arigid azobenzene as another part of the mesogenic unit were synthesized by interfacialpolymerization of diacyl chlorides in 1, 2-dichloroethane and 2, 4-dihydroxy-4'-nitroazobenzen inaqueous alkaline solution. The polyester structures were confirmed by proton NMR and IRspectra. Their phase transition behavior and texture were studied by polarizing microscopy andDSC.
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.
基金This work was supported by the National Natural Science Foundation of China(Grant No.20134010)the Ministry of Education of China(Key Project No.104005).
文摘A series of poly{2,5-bis[(4-butoxyphenyl)-oxycarbonyl]styrenes}(PBPCS)with low mo-lecular weight distribution was synthesized by atom transfer radical polymerization(ATRP).The me-somorphic properties were investigated by differential scanning calorimetry(DSC),polarizing optical microscopy(POM)and rheometer.PBPCS showed the phase transition from isotropic into liquid crystal(LC)phase,and the LC phase formed at high temperature and disappeared in the subsequent cooling procedure.Using the WAXD fiber pattern,the phase structure of the PBPCS at higher tem-perature showed hexagonal columnar nematic phase.Experimental results demonstrated that the driving force of the entropy is an important factor during the unusual LC phase formation of PBPCS.
基金Supported by the National Natural Science Foundation of China(Grant No.59803002) and the State EducationalMinistry for the Ove
文摘The present paper covers the phase behavior of poly(pbenzamide)(PBA)/Nylon 6/H 2SO 4 and poly(pphenylene terephthalamide) (PPTA)/Nylon 6/H 2SO 4 systems. The transition temperatures detected by the Depolarized Light Intensity measurements were used to construct the phase diagram in which the influence of temperature was shown. The enhanced depolarized light intensity observed in the ternary system suggests that the coil polymer chains may tend to be extended and contribute to the overall anisotropy of the liquid crystal phase.
文摘Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place over the entire temperature range between its meltingpoint and clearing point and the orientation level is strongly temperature-dependent, thedevelopment with time of the magnetic orieatation follows an exponeotial-type relation,and the smectic phase state influences the thermal relaxation process in the absence of themagnetic field.
文摘Photochromism is the reversible structural change of the molecules upon light irradiation having different spectral pattern before and after irradiation. Liquid crystal (LC) is a long-range orientational order of the molecules in between solid and isotropic liquid phases which share the properties of the crystal and liquid phases. 1-Alkyl-2-(ary-lazo)imidazoles, (Raai-CnH2n+1, R = H, Me and n = 10, 12, 14, 16, 18, 20, 22) exhibits photochromism and two of them (Haai-C18H37 and Haai-C22H45) show Liquid crystal (LC) properties. One of these compounds, Meaai-C16H33 is structurally characterized by single crystal X-ray diffraction study. The compounds upon irradiation with UV light show E-to-Z isomerisation. Quantum yields (φE→Z) of E-to-Z isomerisation vary with the molar mass of the compounds. The reverse transformation, Z-to-E, is recorded in thermal condition. The activation energy (Ea) of isomerisation is determined by the controlled temperature reaction. Liquid crystal property of the molecules is examined by polarizing optical microscopy (POM) and DSC. The carbon chain length n = 18 shows nematic (N)-isotropic (I) phase transition and an unknown Smectic (Sm) phase is observed with n = 22 on heating cycle.
文摘Various characteristics of mesomorphism can be explained using intermolecular interactions between a pair of liquid crystalline molecules. The intermolecular interactions have been calculated considering multipole-multicentere expansion method and modified by second order perturbation treatments. For calculation of multipole i.e. charge, dipole, etc. at each atomic center of molecules, para-butyl-p’-cyano-biphenyl, GAMESS, an ab initio program, with 6-31G* basis set has been used. The stacking, in-plane and terminal interaction energies explain the liquid crystalline behaviour of the system.
文摘In this paper,we study the isotropic-nematic phase transition for the nematic liquid crystal based on the Landau-de GennesQ-tensor theory.We justify the limit from the Landau-de Gennes flow to a sharp interface model:in the isotropic region,Q≡0;in the nematic region,theQ-tensor is constrained on the manifolds={s_(+)(n−1/3I),n∈S^(2)}with s_(+) positive constant,and the evolution of alignment vector fieldobeys the harmonic map heat flow,while the interface separating the isotropic and nematic regions evolves by the mean curvature flow.This problem can be viewed as a concrete but representative case of the Rubinstein-Sternberg-Keller problem introduced in Rubinstein et al.(SIAM J.Appl.Math.49:116-133,1989;SIAM J.Appl.Math.49:1722-1733,1989).
基金supported by the National Natural Science Foundation of China(No.51303177)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB12020300)
文摘In this work, the mesophase properties were tuned via mixing two discotic molecules with structural complementarity. Compared with the liquid crystalline hexakis(n-hexyloxy)triphenylene(H6TP)materials(columnar hexagonal phase from 53 ℃ to 91 ℃), mesophase types as well as phase transition temperatures varied with the introduction of crystalline hexaazatriphenylene derivative(PBH)molecules. The introduction of less than 33% amount of PBH disrupted the columnar hexagonal phase formed by H6 TP remarkably, followed by the decreased clearing temperatures of liquid crystals. As the PBH amount was further increased, the destroyed columnar hexagonal phase was turned into the columnar rectangular phase, in which H6 TP and PBH molecules together formed the columnar mesophase. The formation of new mesophase contributed to the enlarged mesophase temperature(from44 ℃ to 144 ℃). We speculated that the alkyl chains interaction induced by the PBH component competed with the strong p–p stacking between H6 TP molecules, thus altering the liquid crystalline properties including mesophase types and phase transition temperatures.
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.
文摘The synthesis and characterization of novel Schiff base liquid crystalline crown ethers prepared from the inter-mediates 4-(4-alkoxylbiphenyl-4-carbonyl)benzaldehyde, cis- and trans-4,4-diaminodibenzo-18-crown-6 are de-scribed. The structure of these compounds have been well characterized by elemental analysis, IR, 1H NMR and MS spectroscopy. The liquid-crystalline behavior of these compounds was also inverstigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) with a heating stage and polarimetric analysis.
基金supported bythe National Natural ScienceFoundation of China(Nos.21875143and21875157)the InnovationResearch Foundationof Shenzhen(No.JCYJ20180507182229597)the Natural Science Foundation of Guangdong Province(No.2016-A030312002)and theopen foundation of State Key Laboraatory of Chemical Engineering(No.SKL ChE-20B04).
文摘Molecular motions of the luminescent liquid crystals(LLCs)show a significant effect on fluorescent emission and heat generation.In this article,a series of cyanostilbene-based LLCs(CSs:CS1-6,CS1-12,CS2-6 and CS2-12)are synthesized to investigate how the pho-toluminescence and photothermal effect balanced.Among these materials,the mesogens peripheried by single alkyl chains formed enantiotropic nematic(CS1-6)or smectic C(CS1-12)phase with different alkyl tail lengths.When the single aliphatic chain is re-placed by mini-dendrons,room temperature(RT)monotropic hexagonal columnar phase(CS2-12)or molecular liquid(CS2-6)is formed.The results revealed that all these materials exhibited high efficiency emission with the highest quantum yield reaching 59.0%.The photoluminescence and photothermal effect can be effectively tuned by dispersing CSs into a commercially available RT liquid crystal matrix 8CB,which output significantly improved photothermal conversion efficiency of 63.2%.Furthermore,the pho-tothermal can rapidly trigger the Smectic A-Nematic-Isotropic sequence transitions of 8CB doped with CSs.This work paves a way of adjusting the balance of photoluminescence and photothermal properties of the LLC materials.
基金The authors gratefully acknowledge the support of National Natural Science Foundation of China (No. 21272080), Department of Science and Technology, Guangdong Province (Nos. 2010A020507001-76, 5300410, FIPL-05-003) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry.
文摘A series of novel tolane-type liquid crystals with amide group as terminal group have been prepared. The terminal amide groups were modified, and the influence of these structural parameters on liquid crystal phases was investigated by polarizing optical microscope (POM) and differential scanning calorimetry (DSC). Three of these new compounds exhibit nematic phase, good thermal stabilities. In general, these liquid crystals with amide as end groups have high melting points and phase transition temperatures, which result from the hydrogen bonds. Based on theoretical calculations, these new molecules with strong electron donating amide as end group have narrower HOMO-LUMO energy gap and higher dipole moment than tolane.