Solid-State polymerization of the binary mixture of methacrylate and liquid-crystalline compound by electron beam

Solid-state polymerization of a binary mixture of nonliquid-crystalline monomer and liquidcrystalline compound was carried out using electron beam. The monomers were benzoic acid containing 4-[ω-(meth)acryloyloxyalkyloxy] benzoic acids, in which the alkylene spacer was ethylene, hexamethylene, or undecamethylene. The conversion yield of monomer to polymer to a large extent increased with increasing content of a liquid-crystalline compound with a terminal carboxylic group, such as 4-n-alkyloxybenzoic acid, while the addition of a liquid-crystalline compound without terminal carboxylic group did not affect polymerization of the monomer. Phase diagrams of the mixture of monomer and liquid-crystalline compound were examined using cross-polarizing microscopy and differential scanning calorimetry (DSC). All mixtures of monomer and 4-n-alkyloxybenzoic acid or liquid-crystalline compound without terminal carboxylic group showed liquid-crystallinity in a broad composition range. It was concluded that liquid-crystalline compounds with terminal carboxylic acid may form hydrogen bondings with methacrylate or acrylate monomer having terminal carboxylic acid which enhance polymerizability of the mixture. The stereoregularity of polymers determined by NMR depended on increasing irradiation dose and temperature rather than the content of the added liquid-crystalline 4-n-decanoxybenzoic acid.     

Discotic charge transfer twins Structure and mesophase behaviour of covalently linked triphenylenes and trinitrofluorenones

Discotic charge transfer twins, a novel class of discotic liquid-crystalline compounds were studied. These compounds consist of triphenylene units (as donors) which are chemically linked via flexible spacers of various lengths to trinitrofluorenone units (acting as acceptor). They display a liquid-crystalline phase over a wide temperature range extending up to 240-260°C. Based on X-ray analysis a structural model is proposed for the liquid-crystalline phase: the molecules are arranged in columns in such a way that mixed stacks occur, the intercolumnar packing possesses an orthorhombic symmetry. The neighbouring columns are connected along specific directions via flexible spacers which give rise to highly anisotropic structural properties of this columnar liquid-crystalline phase.     

Neutral-carrier-type potassium ion-selective electrodes based on polymer-supported liquid-crystal membranes for practical use.

Polymer-supported liquid-crystal membranes have been designed for neutral-carrier-type potassium ion-selective electrodes, aiming for practical applications of high-performance liquid-crystalline membrane ion sensors. Two types of polymer-supported liquid-crystal membranes were tested for their usefulness; one is microporous poly(tetra fluoroethylene) (PTFE) membranes impregnated by thermotropic liquid-crystalline compounds, and another is poly(methyl methacrylate) (PMMA) membrane dispersing the same liquid-crystalline compounds. Both of the polymer-supported liquid-crystal membranes containing a liquid-crystalline benzo-15-crown-5 neutral carrier as well as a lipophilic anion excluder work well as ion-sensing membranes for potassium ion-selective electrodes, the ion selectivities of which can be switched by the measurement temperatures. Specifically, PTFE-impregnated liquid-crystal membranes are better than the PMMA-dispersed ones in the sensitivity and selectivity of the resulting ion electrodes. A potassium ion assay in blood sera has proved that neutral-carrier-type ion-selective electrodes based on the polymer-supported liquid-crystal membranes are reliable for practical uses.     

X-ray investigation of combined main-chain/side-chain liquid-crystalline polymers

Structural investigations on six combined liquid-crystalline polymers using the X-ray technique are described. The measurements have allowed a characterization of the liquid-crystalline phases and have led to our first ideas about the phase structures. All mesogenic groups are arranged parallel to each other, the shortest segment in the main-chain or in the side-chain determines the smectic layer spacing. A modified designation for liquid-crystalline phases of high polymers is proposed.     

Induction of smectic mesomorphism by mixing a non-liquid-crystalline methacrylate with a nematic liquid-crystalline compound having a cyano-containing mesogen

The structure and phase diagram of a binary mixture of a non-liquid-crystalline, mono-functional (meth)acrylate monomer and a liquid-crystalline compound having a cyano group-containing mesogen were examined. The monomers had mesogenic units such as biphenylene and phenyl benzoate, but did not show liquid-crystallinity. The liquid-crystalline compounds possessed a cyanobiphenyl or a cyanophenyl benzoate mesogenic unit. The liquid-crystalline 4-cyanophenyl 4'-n-octyloxybenzoate did not show a smectic A phase, while the binary mixture of the 4-butoxy-4'-(ω-methacryloyloxyhexyloxy)biphenyl monomer with 4-cyanophenyl 4'-n-octyloxybenzoate showed the induction of a smectic A phase in a nearly equimolar composition range. However, the binary mixture of the monomer, containing a phenyl benzoate group, and the liquid-crystalline compound did not induce a smectic phase.     

Amphotropic liquid-crystalline behaviour of glycolipids in amino acid ionic liquids

We examined lyotropic liquid-crystalline behaviour of glycolipids (GLs) with a normal alkyl chain or a diacetylene-functionalised alkyl chain in several amino acid ionic liquids (AAILs). It was found that the mixtures of GL and AAIL form various nanosegregated liquid-crystalline phases, such as smectic, bicontinuous cubic and hexagonal columnar phases, depending on the two-component ratio and AAIL species. The observed liquid-crystalline behaviours were summarised as phase diagrams. It is noteworthy that the employment of amino acid anions with superior hydrogen-bonding ability, such as aspartic and glutamic acid anions, gives a phase diagram with a wide liquid-crystalline region. Comparing with a phase diagram obtained for the GL/water mixtures, we gained insights on the similarity/dissimilarity between water and AAILs as self-organisation media of amphiphiles. For the diacetylene-functionalised molecule, UV irradiation was carried out to progress polymerisation. It is of interest that the polymerisation reaction progressed when the glycolipid formed a smectic phase in an AAIL while a reaction progress was not found when it formed a bicontinuous cubic phase in another AAIL. We believe that AAILs have a great potential to be a liquid media not only for amphiphiles but for various functional materials, such as polymers and colloids, to form novel assemblies.     

Curing kinetics of liquid-crystalline epoxy resins

By endcapping mesogenic rigid rod molecules with reactive epoxy groups a novel class of liquid-crystalline thermoset has been obtained. In fact is has been shown that the nematic molecular arrangement is sustained over the crosslinking reaction of liquid-crystalline epoxy resins when the curing reaction is carried out in the thermal stability range of the liquid-crystalline phase. Calorimetric analysis was used in characterizing the isothermal cure. An unsophisticated model is proposed for evaluating the activation energies of the crosslinking reaction. For liquid-crystalline epoxy resins lower activation energies result with respect to the cure reactions for non liquid-crystalline epoxy resins.     

Evaluation of the Effect of Citronellol Group on Functionalized Mesogenic Materials by Capillary GC

In this paper, the effects of functionalization with terpenes on two new liquid-crystalline stationary phases for gas chromatography (GC) are described. Citronellol was used as the terminal group in the first material, and tetrahydrogeraniol was used with a second material. Inverse GC showed that the new materials have wide liquid-crystalline ranges (mesophases), 371–500 and 395–501 K, respectively. Moreover, they show good thermal stability up to 523 K and good potential as stationary phases for capillary GC. To clarify the effects of the liquid crystal structures and functional groups on retention and separation, the chromatographic behaviors of the two stationary phases were compared by eluting alkylbenzenes, polycyclic aromatic hydrocarbons, aromatic compounds, and terpenoids. The selectivities for a wide range of analytes achieved using the citronellol column were significantly better than those obtained using the tetrahydrogeraniol column. The columns showed different retention behaviors and fine resolutions for some of the main constituents of essential oils. Introduction of the double bond of citronellol greatly improved the polarization interactions involved in the shape recognition of the liquid-crystalline state for isomers. The new citronellol liquid-crystalline stationary phase, therefore, has a high affinity for natural compounds.

     

Hybrid thermotropic liquid-crystalline block copolymers

A new approach to the preparation of two classes of block copolymers containing liquid-crystalline segments is reported. Copolymers 1 and 2 are constituted by polytetrahydrofuran and side-chain liquid-crystalline polymethacrylate blocks, whereas block copolymers 3 consist of polystyrene and main-chain liquid-crystalline polyester blocks. The synthetic procedures leading to copolymers 1-3 are extremely versatile and can be used to prepare a great variety of block copolymer architectures. In both copolymer classes the chemically different blocks are strongly segregated in the solid and melt phases and undergo individual phase transitions. The mesophase transition temperatures of the liquid-crystalline blocks are very similar to those of the corresponding homopolymers, and their enthalpies are directly proportional to the content of the liquid-crystalline block.     

掺杂聚苯胺溶致液晶相的产生和表征

聚苯胺（PAN）具有共轭结构,从理论上满足形成液晶相的基本条件［1,2］．但由于聚苯胺难溶、难熔,长期以来对于聚苯胺溶液（尤其是浓溶液）或熔体的研究甚少．近年来,人们采用具有“增塑作用”的大分子功能质子酸对聚苯胺进行掺杂,获得可溶于多种有机溶剂中的掺杂态聚苯胺［3～5］．然而,聚苯胺溶液的结构与性能的特点及能否产生溶致液晶相等问题目前尚未见报道．为此,我们研究了十二烷基苯磺酸（DBSA）掺杂聚苯胺在有机溶剂中形成液晶相的条件,探讨了不同掺杂方法对PAN－DBSA的溶解性及形成液晶棺的影响;采用差式扫描量热分…     

Rotational viscosity of ferroelectric liquid-crystalline polysiloxanes

Some physical parameters of comb-shaped ferroelectric liquid-crystalline polymers were measured. Their rotational viscosities are two or three orders of magnitude larger than that of low molecular weight ferroelectric liquid crystals. Furthermore, they are found generally to be proportional to the second power of the weight-average molecular weight. Spontaneous polarization of the ferroelectric liquid-crystalline polymers has little dependence on molecular weight.     

Synthesis and characterization of liquid-crystalline side group polymers with benzylideneaniline as mesogenic moiety

Two new thermotropic liquid-crystalline side group polymers were synthesized, characterized and compared with the liquid-crystalline monomeric analogues. Some packing features of these polymeric liquid crystals are discussed.

Investigations were carried out by differential calorimetry (D.S.C.), polarization microscopic observation and X-ray diffraction on non-aligned and magnetic field-aligned samples in the wide and small angle region.

The synthesized polymers contain as mesogenic moiety a benzylideneaniline group which is attached in the 4 position via a hexamethylene spacer to a poly-methacrylate backbone. The benzylideneaniline group is substituted in 4′ position with an ethoxy or butoxy group (PEt or PBu). The monomeric analogues are denoted MEt and MBu. The two polymers show a phase sequence crystalline-smectic A-nematic-isotropic. The liquid-crystalline temperature range is observed between 90 and 150°C. The monomeric MEt exhibits only a monotropic nematic, MBu an enantiotropic nematic and a smectic A phase.     

Influence of Perfluoroarene–Arene Interactions on the Phase Behavior of Liquid Crystalline and Polymeric Materials

A stabilization of the liquid-crystalline mesophase and thus an enlarged temperature range of the mesogenic phase is achieved by adding perfluorotriphenylene to a chiral liquid-crystalline triphenylene. This mesophase is based on 1:1 perfluoroarene–arene interactions (see picture). In a polymer with triphenylenes as mesogens in the side chains, the addition of perfluorotriphenylene led to crystallization.     

Liquid-Crystalline Polymer Particles Prepared by Classical Polymerization Techniques

Liquid-crystalline polymer particles prepared by classical polymerization techniques are receiving increased attention as promising candidates for use in a variety of applications including micro-actuators, structurally colored objects, and absorbents. These particles have anisotropic molecular order and liquid-crystalline phases that distinguish them from conventional polymer particles. In this minireview, the preparation of liquid-crystalline polymer particles from classical suspension, (mini-)emulsion, dispersion, and precipitation polymerization reactions are discussed. The particle sizes, molecular orientations, and liquid-crystalline phases produced by each technique are summarized and compared. We conclude with a discussion of the challenges and prospects of the preparation of liquid-crystalline polymer particles by classical polymerization techniques.     

Discotic liquid-crystalline side chain polymers with inositol derivatives as mesogens

The synthesis of monofunctionalized myo- and scyllo-inositol derivatives and their attachment as side groups on a polysiloxane backbone are described. All polymers with scyllo-inositol mesogens show liquid-crystalline behaviour. In contrast to this the myo-inosital mesogens containing polymers exhibit no liquid-crystalline phases.     

Rotational viscosity of ferroelectric liquid-crystalline polysiloxanes

Abstract

Some physical parameters of comb-shaped ferroelectric liquid-crystalline polymers were measured. Their rotational viscosities are two or three orders of magnitude larger than that of low molecular weight ferroelectric liquid crystals. Furthermore, they are found generally to be proportional to the second power of the weight-average molecular weight. Spontaneous polarization of the ferroelectric liquid-crystalline polymers has little dependence on molecular weight.     

Synthesis and properties of photochromic liquid-crystalline polyacrylates containing a spirooxazine group

The novel photochromic liquid-crystalline polyacrylates containing a spirooxazine group were synthesized. The photochromic polymer containing (4-penta- methyleneoxy)biphenylene moiety at the 5-position of spironaphthoxazine showed nematic phase from 122.9 to 133.8°C. The photochromic polymer containing undeca- methylene instead of pentamethylene showed smectic phase from 93.1 to 169.7°C. On the other hand, the photochromic polymer containing both undecamethylene as a spacer and spironaphthoxazine-bound biphenylene moiety at 9′-position did not show any liquid crystallinity. All spirooxazine-containing liquid-crystalline polymers showed photochromism in the solid state at room temperature. Because the shape of the absorption spectra of the photochromic quenched liquid-crystalline polymer films was almost the same as those of the photochromic amorphous polymer films, the photochromic properties did not depend on the mesophase in the polymers examined. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3513–3522, 1999     

Supramolecular liquid-crystalline materials: molecular self-assembly and self-organization through intermolecular hydrogen bonding

Supramolecular liquid-crystals are molecular complexes formed from different and independent molecular species through specific molecular interactions such as hydrogen bonding. We have recently developed new types of H-bonded liquid-crystalline materials obtained by molecular self-assembly processes: (1) doubly H-bonded liquid-crystalline complexes through a molecular recognition process between 2,6-bis(acylamino)pyridines and benzoic acids, (2) liquid-crystalline polymer blends involving an H-bonding interaction between poly(4-vinylphenol) and a thermotropic main-chain polyester containing a lateral pyridyl substituent, (3) liquid-crystalline networks built through hydrogen bonds between multifunctional H-bonding components. These new materials may bridge a gap between liquid crystals and supramolecular systems.     

High-resolution characterization of liquid-crystalline [60]fullerenes using solid-state nuclear magnetic resonance spectroscopy

Liquid-crystalline materials containing fullerenes are valuable in the development of supramolecular switches and in solar cell technology. In this study, we characterize the liquid-crystalline and dynamic properties of fullerene-containing thermotropic compounds using solid-state natural abundance (13)C NMR experiments under stationary and magic angle spinning sample conditions. Chemical shifts spectra were measured in isotropic, liquid-crystalline nematic and smectic A and crystalline phases using one-dimensional (13)C experiments, while two-dimensional separated local-field experiments were used to measure the (1)H- (13)C dipolar couplings in mesophases. Chemical shift and dipolar coupling parameters were used to characterize the structure and dynamics of the liquid-crystalline dyads. NMR data of fullerene-containing thermotropic liquid crystals are compared to that of basic mesogenic unit and mesomorphic promoter compounds. Our NMR results suggest that the fullerene-ferrocene dyads form highly dynamic liquid-crystalline phases in which molecules rotate fast around the symmetry axis on the characteristic NMR time scale of approximately 10 (-4) s.     

Laterally attached liquid-crystalline polymers as stationary phases in reversed-phase high-performance liquid chromatography. III. Effect of the local anisotropic order on the separation of polycyclic aromatic hydrocarbons

Specific stationary phases based upon non-liquid-crystalline polymers, liquid-crystalline molecules and side-on fixed liquid-crystalline polymers (SO-LCP) have been synthesized for use as silica modified stationary phases in high-performance liquid chromatography (HPLC). The mesogenic side group of the SO-LCP was composed of three phenyl ring benzoate type with terminal alkoxy chains and was laterally linked to a polysiloxane backbone via an alkyl ester spacer arm. This study demonstrated that the shape recognition of stationary phases based upon SO-LCP towards the length-to-breath ratio (L/B) was strongly connected to the existence of a local liquid-crystalline order into the pores of silica gel, warranting the interest of the collective organization of mesomorphic materials in liquid chromatography. Furthermore, the chromatographic performances depended on the kind of anisotropic order and it was more advantageous to use smectic side-on liquid-crystalline polymer than nematic and obviously non-liquid-crystalline ones. Finally, for a series of polymers having the same mesomorphism, the larger the temperature stability range of the mesophase, the more pronounced the local order effect and the higher the shape recognition.