偶氮功能化液晶高分子的研究进展

结合一些研究结果,综述了近年来偶氮功能化液晶高分子的研究近况和合成技术进展,重点讨论了主链型偶氮液晶高分子,侧链型偶氮液晶高分子,树枝状偶氮液晶高分子以及香蕉型偶氮液晶高分子的分子结构设计,合成工艺方法和主要性能。同时对偶氮功能化液晶高分子的发展趋势及应用前景进行了分析和展望。     

液晶高分子的分子设计

简单介绍了液晶高分子的结构特点，分类及其应用状况，详细介绍了主链型和侧链型液晶高分子设计的新进展，根据溶臻主链型液晶高分子和热臻主链型液晶高分子分子结构的不同，提出今后设计主链液晶高分子的主要任务，从主链结构，液晶基元类型和柔性间隔出发介绍了侧链液晶高分子分子设计的关键，最后介绍了液晶高分子分子设计的发展趋势。     

五种新型高分子液晶研究进展及应用前景

阐述了高分子液晶的形成条件,综述了纤维素液晶、甲壳素液晶、铁电液晶、盘状液晶、卤代液晶等五种新型高分子液晶材料的结构、性能及其应用前景,并对高分子液晶的发展方向进行了展望。     

向列型含氟侧链高分子液晶的合成与表征

合成了4-(丙烯酸乙氧基酯)苯甲酸,4-(丙烯酸乙氧基酯)苯甲酰氧基苯甲酸等系列液晶中间体.首次合成了4-(丙烯酸乙氧基酯)苯甲酰氧基苯甲酸基元的含氟侧链高分子液晶,采用IR,1HNMR和19FNMR表征了其分子结构.通过DSC分析和偏光显微镜研究了含氟侧链高分子液晶的织构形态.结果表明,4-(丙烯酸乙氧基酯)苯甲酰氧基苯甲酸基元含氟侧链高分子液晶具有向列型液晶的织构形态.4-(丙烯酸乙氧基酯)苯甲酰氧基苯甲酸基元含氟侧链高分子液晶,其液晶温度范围较宽,随着液晶基元成分的降低,含氟侧链成分的增加,高分子液晶玻璃化温度略有降低.     

热致性芳香族聚酯液晶的发展

本文对芳香族聚酯(即聚芳酯)液晶高分子的发展和应用进行了研究,对市场上比较常见的几种主链芳香族聚酯液晶高分子进行了比较详细的剖析。并以Vectra为例,对芳香族聚酯液晶高分子的发展趋势做了简述。     

高分子液晶材料的应用及发展趋势

液晶相是不同于固相和液相的一种中介相态。系统地阐述了液晶的发现、形成机制以及分类,简单介绍了液晶高分子的结构特点,介绍了主链型和侧链型液晶高分子研究的新进展,并对液晶在各个领域的应用研究和潜在性能进展作了简要的阐述。     

苯并菲类高分子液晶材料的研究进展

苯并菲类衍生物因其优异的柱状相液晶性质和良好的自组装能力,被广泛应用于光电材料,并得到有机合成和光电材料工作者的广泛关注和深入探究。作为苯并菲类衍生物的一个重要分支,高分子液晶材料受到了越来越多的关注。简单介绍了苯并菲类高分子液晶的分类、性质以及各类高分子结构对其液晶性质的影响,对苯并菲类液晶高分子材料的发展历程做简单的综述。     

液晶高分子及其应用

液晶高分子是一类较新的高分子材料,是一类大规模研究工作起步较晚的液晶材料,但由于其本身无与伦比的优点,以及与信息技术、新材料和生命科学相互促进作用,已成为世纪之交的热点之一。简要介绍了液晶高分子聚合物的类型、特性、主要应用以及液晶高分子设计的前景。     

高β晶含量的聚丙烯/液晶高分子复合材料及制备

<正>本发明公开了高β晶含量的聚丙烯/液晶高分子复合材料及其制备方法,属于聚丙烯增韧改性领域。将等规聚丙烯、液晶高分子成核剂和功能助剂在高速混合机内混合均匀,并在双螺杆挤出机中熔融挤出造粒,得到高β晶含量的聚丙烯/液晶高分子复合材料。所制聚丙烯/液晶高分子复合材料中β晶相对含量在90%以上,与纯聚丙烯相比,聚丙烯/液晶高分子复合材料具有更     

聚酯液晶高分子的开发及应用

介绍了液晶高分子的结构以及分类,着重阐述了以芳香族聚酯为主链的液晶高分子的合成,工业化产品,以及其性能,应用领域和改性研究等。     

Material design for polymer/azobenzene liquid crystal/metal salt composite films possessing thermo- and photoresponsive ionic conductivity

Various azobenzene derivatives and polymers were attempted as materials for thin composite films containing a polymer, a liquid crystal, and lithium perchlorate which can undergo ionic-conductivity switching induced by light or heat. Poly(vinyl chloride) -based composite films containing enantiotropic azobenzene liquid crystals 1 , exhibited significant ionicconductivity change based on thermo- and photoinduced phase transitions of 1 , the temperature dependence on the ionic conductivity reflecting the enantiotropic phase transition behavior of the liquid crystals. Marked, reversible ionic-conductivity switching on alternating irradiation of UV and visible lights was attained with the composite films containing 1 , especially 1 (n = 12). Incorporation of monotropic liquid crystals 3 to the composite films allowed bistability in the temperature dependence on the ionic conductivity. Employment of a polycarbonate resin and poly(methyl methacrylate) as the polymer material of the composite films gave similar ionic-conductivity changes to the poly(vinyl chloride) composite films, whereas polyethyleneoxide brought about some different results in the photoinduced ionic-conductivity change.     

Intriguing liquid crystalline behavior of liquid crystalline polyrotaxane containing azobenzene mesogens

A series of liquid crystalline polyrotaxanes containing azobenzene mesogenic moieties (AzoPR) with different length of spacer were synthesized, and the relationship between the spacer length and the liquid crystalline behavior was investigated. The molecular characterization of the AzoPR was performed with ¹H NMR, FT-IR, and gel permeation chromatography. The thermal stability was investigated via thermogravimetric analysis. Their phase structures and liquid crystalline properties were studied by differential scanning calorimetry, polarized optical microscopy and wide-angle X-ray diffraction. The experimental results suggested that AzoPR with spacer length of 2 and 4 failed to show the liquid crystalline behavior, and AzoPR with spacer length of 6 showed the columnar nematic phase. However, when the spacer length increases to 11, the columnar nematic phase formed, meanwhile, the liquid crystalline domains with high ordered structure were developed by azobenzene mesogens.     

Synthesis and characterization of novel monomers and polymers containing chiral (−)-menthyl groups

To investigate the steric effects of chiral menthyl groups on the induction of cholesteric liquid crystals and the sensitivity of the photoisomerizable azobenzene derivatives, a series of chiral monomers and a photoisomerizable chiral azobenzene derivative with various spacers end-capped with (−)-menthyl group were synthesized. The structures of the novel chiral compounds synthesized in this investigation were identified using ¹³C NMR, FTIR, and elemental analysis. The phase transition temperatures of the chiral compounds were investigated using X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy. The thermogravimetric characteristics, the glass-transition temperatures (T_g) and the weight-average molecular weights (M_w) of the homopolymers were also evaluated. Polymers containing chiral menthyl groups with a biphenyl segment were found to reveal high thermal resistance. However, the existence of the steric hindered menthyl group disturbed the arrangement of chiral monomers leading to the disappearance of liquid crystal phases. The specific optical rotation of the synthesized monomers and polymers were also evaluated. The effect of the synthesized chiral compounds, monomers and photoisomerizable azobenzene derivative on the induction of the cholesteric liquid crystal films was investigated. The morphological network structure of the polymer matrix inside a liquid crystal cell was studied using a scanning electron microscope (SEM). The phototuning ability of the AzoM on the cholesteric liquid crystals was also established.     

Synthesis and characterization of fluorine‐containing liquid crystalline polysiloxanes bearing cholesteryl cinnamate mesogens and trifluoromethyl‐substituted mesogens

Several novel side‐chain liquid crystalline (LC) polysiloxanes bearing cholesteryl cinnamate mesogens and trifluoromethyl‐substituted mesogens were synthesized by a one‐step hydrosilylation reaction with poly(methylhydrogeno)siloxane, a cholesteric LC monomer cholesteryl 3‐(4‐allyloxy‐phenyl)‐acryloate and a fluoro‐containing LC monomer 4‐[2‐(3‐trifluoromethyl‐phenoxy)‐acetoxy]‐phenyl 4‐allyloxy‐benzoate. The chemical structures and LC properties of the monomers and polymers were characterized by use of various experimental techniques, such as FTIR, ¹H‐NMR, ¹³C‐NMR, TGA, DSC, POM, and XRD. The temperatures at which 5% weight loss occurred were greater than 300°C for all the polymers, and the residue weight near 600°C increased slightly with increase of the trifluoromethyl‐substituted mesogens in the fluorinated polymer systems. The samples containing mainly cholesteryl cinnamate mesogens showed chiral nematic phase when they were heated and cooled, but the samples containing more trifluoromethyl‐substituted mesogens exhibited chiral smectic A mesophase. The glass transition temperature of the series of polymers increased slightly with increase of trifluoromethyl‐substituted mesogens in the polymer systems, but mesophase–isotropic phase transition temperature did not change greatly. In XRD curves, the intensity of sharp reflections at low angle increased with increase of trifluoromethyl‐substituted mesogens in the fluorinated polymers systems, indicating that the smectic order derived from trifluoromethyl‐substituted mesogens should be strengthened. These results should be due to the fluorophobic effect between trifluoromethyl‐substituted mesogens and the polymer matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Alignment Photoregulation of a Nematic Liquid Crystal by Surface Adsorption of Aminoalkylated Azobenzenes

Adsorption behavior of azobenzenes having an aminoalkyl residue onto a silica surface is described. Immersion of a silica plate in a benzene solution of an aminoalkylated azobenzene resulted in efficient adsorption to form face-to-face aggregates which are converted into monomeric states by partial desorption. Silica plates adsorbing the azobenzene bearing an aminoalkyl residue were employed to achieve the surface-assisted photoregulation of alignment of a nematic liquid crystal between homeotropic and planar modes. Based on these observations, a convenient method to prepare command surfaces for the orientational photoregulation of liquid crystals was presented by filling a liquid crystal containing an aminoalkylated azobenzene into an empty cell composed of clear silica plates.     

Synthesis and physical properties of liquid‐crystalline copolymers with azobenzene segments

To investigate the effects of photoisomerizable azobenzene segments on the liquid‐crystalline characteristics and thermal properties of polymers, a series of liquid‐crystalline homopolymers and copolymers with azobenzene segments was synthesized. The azobenzene contents of the copolymers were estimated with elemental analysis. The photoisomerization of the azobenzene derivatives was studied with ultraviolet–visible (UV–vis) spectroscopy. The UV–vis absorption of the copolymers was found to be parallel with the content of the azobenzene segments. UV irradiation was found to cause a decrease in the copolymer transmittance around 355 nm due to the photoinduced isomerization from entgegen (E) to zusammen (Z). The phase‐transition temperatures and molecular weights of the polymers were investigated with differential scanning calorimetry and gel permeation chromatography, respectively. The variation in the phase‐transition temperature of the homopolymers before and after UV (365 nm) irradiation was investigated. The bended Z structure was found to disturb the order of the orientation of liquid crystals and to lower the phase‐transition temperature. The appearance of the polymer film was changed from opaque to clear after sufficient UV irradiation. The image recording of the polymer films was achieved after UV irradiation through a mask with pictures. The stability and reliability of the Nematic‐Isotropic phase transition of the homopolymers was evaluated with repeated cycles of 365‐nm UV irradiation and heating at 130°C. After the recycle phase transition was repeated nine times, no significant decay in the response and transmittance could be found. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 2006     

Understanding Photomechanical Behavior of Liquid Crystalline-Based Actuators

Liquid crystalline-based actuators containing azobenzene photoswitches have been used to demonstrate light-responsive motion in soft actuator systems. Understanding the mechanical performance of these light-responsive actuators as a function of the polymer chemistry as well as the nature and concentration of the photoswitches is crucial for developing advanced applications. A systematic study is presented here that clarifies the role of azobenzene photoswitches and the liquid crystalline networks in generating the desired photomechanical performance. Through measurement of photo stimulated mechanical behavior, in particular generated force and strain, a generalized set of guidelines concerning the appropriate subset of polymer chemistry and photoswitches required to achieve the desired performance for actuator design is derived.     

Unusual chain configuration of main-chain liquid crystal polyesters having Y-shaped mesogens in nematic phase

The nematic liquid crystals of main-chain liquid crystalline (MCLC) Y-n polyesters were investigated and compared with those of conventional MCLC L-n polyesters. Y-n polyesters have Y-shaped mesogens that are connected by spacers at their branch ends as an alternative to the columitic mesogens of L-n polyesters. The nematic phases of both polyesters under polarized optical microscopy exhibited Schlieren textures that are typical of uniaxial nematic liquid crystals. The isotropization temperature and entropy change estimated by differential scanning calorimetry show odd-even oscillations, which are characteristic of MCLC polymers, and the entropy change of Y-n are significantly smaller than those of L-n. Such a low entropy change is associated with the Y-n chain configuration, which is unusual for MCLC polymers, as revealed by X-ray diffraction and infrared dichroic spectroscopy. The uniaxial nematic structure is formed by Y-shaped mesogens arranging their trunks along the director direction and being rotated about their trunks without any correlation. Connecting these mesogens by using spacers that are placed preferentially along the director enables us to depict the chain that oscillates along the director direction and performs a random walk in the direction perpendicular to the director.     

Fabrication of surface‐relief gratings on an azobenzene‐containing epoxy‐based polymer film using atomic force microscopy

Many studies have been reported on the photo‐fabrication of surface‐relief gratings (SRGs) in azo‐polymer films using the interference of two laser beams of appropriate polarization. However, there are few reports in the literature concerning the electro‐fabrication of SRGs on such types of polymer films. The goal of the work reported was the electro‐patterning of an azobenzene‐containing epoxy thermoplastic film. An epoxy‐based polymer functionalized with an azo‐chromophore was synthesized and characterized using thermal analysis. The reversible optical storage properties and photo‐induced dichroism were studied. SRGs were fabricated on a film of the synthesized azobenzene‐containing polymer using contact mode current‐sensing atomic force microscopy which locally applied an electric field that aligned the azobenzene moieties. The anisotropic mass transport of the azo‐polymer film was observed after applying an electric field. Additionally, the effect of the relief formation in the polymeric film surface was investigated by means of atomic force microscopy and electrostatic force microscopy. Copyright © 2010 Society of Chemical Industry     

Photo-Orientation at the Interface between Thermotropic Nematic Liquid Crystal and Water Caused by Azobenzene Polymer Additives

Photoinduced orientational transitions in a thermotropic nematic liquid crystal caused by modulation of the boundary conditions at the water surface were observed and investigated. The initially degenerated planar anchoring of liquid crystal at the water surface becomes homeotropic under near-UV irradiation which induces photoizomerization of comb-shaped azobenzene polymer additives adsorbed from the liquid crystal to its interface with water. After irradiation, the photoinduced orientational structures spontaneously relax to the initial ones. It was shown that the orientational sensitivity to light irradiation strongly depends on the polymerization degree of azobenzene additives.