Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopan...Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopant and monomer concentrations on the electro-optical properties, such as contrast ratio, driving voltage, hysteresis width and response time, are investigated. The reasons of electro-optical properties influenced by the concentrations of the materials are discussed. Through the proper material recipe, the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.展开更多
Liquid crystal（LC） compound with isothiocyanate and naphthyl group is an attractive high birefringence LC material,and can be used in optical devices. In this paper, the electro-optical properties of a series of thi...Liquid crystal（LC） compound with isothiocyanate and naphthyl group is an attractive high birefringence LC material,and can be used in optical devices. In this paper, the electro-optical properties of a series of this type of LC compounds were investigated. The melting points and enthalpy values of these LC compounds were higher than those of corresponding compounds with the phenyl group. These compounds exhibited high birefringence with a maximum value of 0.66. Fluorine substitution in the molecular almost does not affect the birefringence value. When these LC compounds with the naphthyl group were dissolved in a commercial LC mixture, the electro-optical properties depending on temperature were investigated. In the low-temperature region, LC mixtures with the naphthyl-group LC compounds exhibited higher viscosity than pure commercial LCs. In the high-temperature region, viscosity values very closely approached each other. When response performance was investigated, figure-of-merit（FoM） values were measured. The Fo M values of LC mixtures containing LC compounds with naphthyl group were lower than those of reference benzene LCs in the low-temperature region. However, in the high-temperature region, the results were reversed. These isothiocyanate LC compounds with naphthyl group can be applied in special fast-response LC device, particularly the ones used under high-temperature conditions.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
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
Excellent electro-optical （E-O） performances are essential for high-quality reflective cholesteric liquid crystal （LC） displays, but are often limited by the high driving voltages required by these displays. Dispe...Excellent electro-optical （E-O） performances are essential for high-quality reflective cholesteric liquid crystal （LC） displays, but are often limited by the high driving voltages required by these displays. Dispersing functional nanomaterials into the LCs has emerged as a promising approach to achieve outstanding E-O properties. In this work, we report the facet-controlled E-O properties of a chiral nematic LC （N＊LC） doped with cubic, octahedral, and rhornbic dodecahedral Cu20. The outstanding E-O properties of the doped systems are related to the interaction between the liquid crystals and Cu20 dopants with different exposed crystal planes. Doping with octahedral and rhombic dodecahedral Cu20 reduces the stability of the planar state, as a result of both the surface abundance of active Cu atoms that interact with the polarized LC molecules, and the large amounts of vertexes and edges on the crystal surfaces, which accelerate the transition from the planar to the focal conic state under an applied electric field. Rhombic Cu20 is the most effective dopant for improving the E-O properties of the present LCs, resulting in a 65.31% reduction of the threshold voltage. The facet and morphology effects highlighted in this work provide a new pathway to develop excellent energy-saving meso-materials with exposed high-reactivity facets, improving their potential applications in electro-optical technologies and information displays.展开更多
Nanoparticles （NPs） with flower-like and frame morphologies were synthesized from CuS, a remarkable transition-metal sulfide. We introduced two kinds of CuS NPs into a nematic liquid crystal （LC） 4-cyano-4＇-n-pen...Nanoparticles （NPs） with flower-like and frame morphologies were synthesized from CuS, a remarkable transition-metal sulfide. We introduced two kinds of CuS NPs into a nematic liquid crystal （LC） 4-cyano-4＇-n-pentylbiphenyl （5CB） and investigated the morphology- and concentration-dependent alignment and electro-optic （E-O） effects of CuS NPs on 5CB. A trace amount of flower-like CuS NPs induced a uniform homeotropic orientation of LC molecules; this is attributable to the obtained desirable compact nanosheet structure. Moreover, both flower-like and frame CuS NPs induced a remarkable improvement in the E-O properties of 5CB, and the flower-like CuS/5CB system exhibited a better performance. The doped CuS NPs in the LC host suppressed the shielding effect and strengthened the electric field, resulting in outstanding E-O properties. At a doping concentration of 0.05 wt.%, CuS NPs were well-dispersed and achieved the optimum E-O performance. This study provides a novel method for inducing a uniform orientation and enhanced E-O properties of LC molecules by doping with extraordinary CuS NPs, leading to potential applications in establishing flexible LC displays.展开更多
This Letter introduces the design and simulation of a microstrip-line-based electro-optic （EO） polymer optical phase modulator （PM） that is further enhanced by the addition of photonic crystal （PhC） structures t...This Letter introduces the design and simulation of a microstrip-line-based electro-optic （EO） polymer optical phase modulator （PM） that is further enhanced by the addition of photonic crystal （PhC） structures that are in close proximity to the optical core. The slow-wave PhC structure is designed for two different material configurations and placed in the modulator as a superstrate to the optical core; simulation results are depicted for both 1D and 2D PhC structures. The PM characteristics are modeled using a combination of the finite element method and the optical beam propagation method in both the RF and optical domains, respectively. The phase-shift simulation results show a factor of 1.7 increase in an effective EO coefficient （120 pm/V） while maintaining a broadband bandwidth of 40 GHz.展开更多
基金Project partially supported by the National Natural Science Foundation of China （Grant Nos. 60736042, 60578035 and 50703039） and the Science Foundation of Jilin Province of China （Grant Nos. 20050520 and 20050321-2）.
文摘Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopant and monomer concentrations on the electro-optical properties, such as contrast ratio, driving voltage, hysteresis width and response time, are investigated. The reasons of electro-optical properties influenced by the concentrations of the materials are discussed. Through the proper material recipe, the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61378075,61377032,11604327,and 61475152)the Science Foundation of State Key Laboratory of Applied Optics,China
文摘Liquid crystal（LC） compound with isothiocyanate and naphthyl group is an attractive high birefringence LC material,and can be used in optical devices. In this paper, the electro-optical properties of a series of this type of LC compounds were investigated. The melting points and enthalpy values of these LC compounds were higher than those of corresponding compounds with the phenyl group. These compounds exhibited high birefringence with a maximum value of 0.66. Fluorine substitution in the molecular almost does not affect the birefringence value. When these LC compounds with the naphthyl group were dissolved in a commercial LC mixture, the electro-optical properties depending on temperature were investigated. In the low-temperature region, LC mixtures with the naphthyl-group LC compounds exhibited higher viscosity than pure commercial LCs. In the high-temperature region, viscosity values very closely approached each other. When response performance was investigated, figure-of-merit（FoM） values were measured. The Fo M values of LC mixtures containing LC compounds with naphthyl group were lower than those of reference benzene LCs in the low-temperature region. However, in the high-temperature region, the results were reversed. These isothiocyanate LC compounds with naphthyl group can be applied in special fast-response LC device, particularly the ones used under high-temperature conditions.
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.
文摘Excellent electro-optical （E-O） performances are essential for high-quality reflective cholesteric liquid crystal （LC） displays, but are often limited by the high driving voltages required by these displays. Dispersing functional nanomaterials into the LCs has emerged as a promising approach to achieve outstanding E-O properties. In this work, we report the facet-controlled E-O properties of a chiral nematic LC （N＊LC） doped with cubic, octahedral, and rhornbic dodecahedral Cu20. The outstanding E-O properties of the doped systems are related to the interaction between the liquid crystals and Cu20 dopants with different exposed crystal planes. Doping with octahedral and rhombic dodecahedral Cu20 reduces the stability of the planar state, as a result of both the surface abundance of active Cu atoms that interact with the polarized LC molecules, and the large amounts of vertexes and edges on the crystal surfaces, which accelerate the transition from the planar to the focal conic state under an applied electric field. Rhombic Cu20 is the most effective dopant for improving the E-O properties of the present LCs, resulting in a 65.31% reduction of the threshold voltage. The facet and morphology effects highlighted in this work provide a new pathway to develop excellent energy-saving meso-materials with exposed high-reactivity facets, improving their potential applications in electro-optical technologies and information displays.
文摘Nanoparticles （NPs） with flower-like and frame morphologies were synthesized from CuS, a remarkable transition-metal sulfide. We introduced two kinds of CuS NPs into a nematic liquid crystal （LC） 4-cyano-4＇-n-pentylbiphenyl （5CB） and investigated the morphology- and concentration-dependent alignment and electro-optic （E-O） effects of CuS NPs on 5CB. A trace amount of flower-like CuS NPs induced a uniform homeotropic orientation of LC molecules; this is attributable to the obtained desirable compact nanosheet structure. Moreover, both flower-like and frame CuS NPs induced a remarkable improvement in the E-O properties of 5CB, and the flower-like CuS/5CB system exhibited a better performance. The doped CuS NPs in the LC host suppressed the shielding effect and strengthened the electric field, resulting in outstanding E-O properties. At a doping concentration of 0.05 wt.%, CuS NPs were well-dispersed and achieved the optimum E-O performance. This study provides a novel method for inducing a uniform orientation and enhanced E-O properties of LC molecules by doping with extraordinary CuS NPs, leading to potential applications in establishing flexible LC displays.
文摘This Letter introduces the design and simulation of a microstrip-line-based electro-optic （EO） polymer optical phase modulator （PM） that is further enhanced by the addition of photonic crystal （PhC） structures that are in close proximity to the optical core. The slow-wave PhC structure is designed for two different material configurations and placed in the modulator as a superstrate to the optical core; simulation results are depicted for both 1D and 2D PhC structures. The PM characteristics are modeled using a combination of the finite element method and the optical beam propagation method in both the RF and optical domains, respectively. The phase-shift simulation results show a factor of 1.7 increase in an effective EO coefficient （120 pm/V） while maintaining a broadband bandwidth of 40 GHz.
