胆甾液晶／聚合物多组分体系的结构与性能研究（Ⅲ）──ChN／poly（MMA－CO－BMA）混合体系的形态结构

应用Ｘ射线衍射、偏光显微镜及电子显微镜研究了胆甾液晶与甲基丙烯酸甲酯（ＭＭＡ）─甲基丙烯酸丁酯（ＢＭＡ）无规共聚物共混体系的形态结构。研究了体系的结晶态及液晶态的行为和共聚物含量及组成对光学织构的影响。     

Liquid crystal-directed assembly and phase morphology of a squaraine dye

The squaraine (SQ) dye, 2,4-bis [4-(N,N-di-n-hexylamino)-2-hydroxyphenyl]squaraine was synthesised, and a series of SQ dye/cholesteryl pelargonate binary mixtures with varying dye concentrations (1%, 3%, 7.5%, 10.8%, 15% and 20% w/w) were prepared. Their phase transitions were investigated using differential scanning calorimetry, polarised light microscopy and X-ray diffraction. The SQ dye itself exhibited no liquid crystalline behaviour. The concentration of the dye in the cholesteric compound proved to have a significant effect on the dye aggregation behaviour and phase transitions in cholesteryl pelargonate, resulting in the appearance of new mesophases and the formation of J- and H-aggregates. The texture morphology, X-ray diffraction data and UV–vis absorbance spectra provide strong evidence of the viability of liquid crystal-directed assembly of the SQ dye.     

6-Hydroxyhexyl 4-(E)-4-alkoxy/halostyryl)benzoates: synthesis,characterisation and study of mesomorphic and fluorescent properties

Hydroxyhexyl esters of alkoxy and halostilbene carboxylic acids were prepared and studied for thermal, liquid crystalline and fluorescent properties. The decomposition temperatures were determined thermogravimetrically and the compounds were found stable at least up to 200°C. Differential scanning calorimetry (DSC) indicated two mesophases in alkoxystilbene caboxylates. The smectic nature of the liquid crystal (LC) compounds was identified from the optical textures and confirmed through X-ray diffraction (XRD) measurements, where SmA, SmB and CrE mesophases were observed. The compounds 3a-g and 3h-k show single absorption maxima in UV-visible spectra at around 338 and 322 nm, respectively. All the alkoxy compounds emit blue light in solution and in solid state in the wavelength range of 422–425 nm.     

Investigations on liquid crystalline partially fluorinated alkyl and succinimidyl benzoates

The synthesis and mesophase properties of partially fluorinated alkoxy-substituted benzoic alkyl and succinimidyl (NHS) esters with one, two and three perfluoroalkyl alkoxy chains are reported. The mesophases were studied using differential scanning calorimetry (DSC), polarizing optical microscopy and X-ray diffraction of non-oriented samples. The SmA phases of the one-chain methyl esters are monotropic, while those of the one-chain NHS esters are enantiotropic. The more wedge-shaped two- and three-chain alkyl esters do not form mesophases, whereas the succinimidyl analogues exhibit hexagonal columnar phases. Their enhanced mesophase stability is caused by the higher polarity of the succinimidyl ring with respect to the alkyl ester groups. Aggregation of the dipolar succinimidyl groups, together with the microsegregation of the lipophilic and fluorophilic segments of the partially fluorinated alkoxy chains, is assumed to lead to a threefold structured morphology in both the SmA and the Col_h phases. This threefold structuring can be regarded as analogous to known morphologies of ABC triblock copolymers.     

Investigations on liquid crystalline partially fluorinated alkyl and succinimidyl benzoates

The synthesis and mesophase properties of partially fluorinated alkoxy‐substituted benzoic alkyl and succinimidyl (NHS) esters with one, two and three perfluoroalkyl alkoxy chains are reported. The mesophases were studied using differential scanning calorimetry (DSC), polarizing optical microscopy and X‐ray diffraction of non‐oriented samples. The SmA phases of the one‐chain methyl esters are monotropic, while those of the one‐chain NHS esters are enantiotropic. The more wedge‐shaped two‐ and three‐chain alkyl esters do not form mesophases, whereas the succinimidyl analogues exhibit hexagonal columnar phases. Their enhanced mesophase stability is caused by the higher polarity of the succinimidyl ring with respect to the alkyl ester groups. Aggregation of the dipolar succinimidyl groups, together with the microsegregation of the lipophilic and fluorophilic segments of the partially fluorinated alkoxy chains, is assumed to lead to a threefold structured morphology in both the SmA and the Col_h phases. This threefold structuring can be regarded as analogous to known morphologies of ABC triblock copolymers.     

Properties of molten carboxylates part 5. A quantitative differential thermal analysis study of mesophase formation in the sytems lead(II)dodecanoate/lead(II) oxide and lead(II)dodecanoate/hendecane

Measurements have been made of the temperatures and enthalpy changes of phase transitions in the systems lead dodecanoate/lead oxide and lead dodecanoate/hendecane. The data have been discussed in terms of the R theory of amphiphylic mesophases. The concepts of the R theory are shown to be useful in the interpretation of phase transitions in molten carboxylate systems.     

STUDIES ON THE KINETICS OF PHASE TRANSITIONS OF A MAIN CHAIN THERMOTROPIC POLYESTER

The kinetics of phase transitions including a transition between mesophases were studied for a main-chain thermotropic polyester by means of DSC and depolarizing transmittance techniques. The isothermal process of these transitions was found to be described by the Avrami equation to high conversions. The Avrami exponents n are about 2,4, 5.3 and 2.2 for liquid crystallization, transition between mesophases and crystallization from mesophase respectively. The liquid crystallization from isotropic liquid phase occurs at very low undercoolings with high transformation rate. This behavior is explained as the results of the smaller value of the surface free energy for mesophase than that for crystallites which is evidenced by the very weak temperature dependence of liquid crystallization rate.     

Effect of a lanthanide ion on the micellation and self-organization of lyotropic liquid crystal systems

Lanthanide-containing lyotropic liquidcrystalline systems were synthesized and their phase behavior, as well as the micellar behavior of aqueous solutions of decaethylene glycol monodecyl ether in the absence and presence of a lanthanide ion, were studied. Tensimetry and conductometry were used to determine the critical micellation concentration, and the values obtained by these methods were found to be in close agreement with each other. Polarization microscopy observations showed that, in concentrated aqueous solutions, ordered lyotropic mesophases arise. The parameters of the phase transitions in the systems under study were determined. The mesophase obtained was demonstrated to have a 2D hexagonal supramolecular structure.     

Gas-liquid chromatographic determination of fatty acid composition of cholesteryl esters in human serum using silica Sep-Pak cartridges

A simple and fast analytical procedure for separation and purification of cholesteryl esters of human serum is described. A single lipid extract, together with spiked cholesteryl pentadecanoate, as an internal standard, was passed through a Silica Sep-Pak cartridge. 1.5% diethyl ester in light petroleum was used to elute cholesteryl esters from the column. The separation was verified with thin-layer chromatography on silica gel using light petroleum-diethyl ether-glacial acetic acid (80:20:1) as a solvent. A very clean thin-layer chromatogram of cholesteryl esters without any additional spots of other lipids was obtained. The cholesteryl esters were quantitated by analyzing their fatty acid composition as methyl esters by gas-liquid chromatography. The coefficients of variation were 0.8--4.9% for the major fatty acids (C16:0, C16:1, C18:1, C18:2, C20:4) and 6.7--30.8% for the minor fatty acids (C18:0 and C20:0). The recoveries for cholesteryl palmitate, cholesteryl oleate and cholesteryl linoleate were 90.7, 92.3 and 91.0%, respectively.     

Thermische Analyse binärer Systeme Organischer Verbindungen,die induzierte smektische Phasen bilden

Zusammenfassung Acht binäre Systeme einer homologen Reihe von Cholesterylestern (Cholesterylpropionat bis Cholesteryldecanoat) mit trans-4-Propylcyclohexyl-4-(trans-4-pentylcyclohexyl) benzoat (Licristal 1223, Merck, Darmstadt) wurden thermomikroskopisch und DSC-analytisch untersucht. In sechs Fällen wurden induzierte smektische A-Phasen mit Umwandlungspunktmaxima festgestellt. Die cholesterischen bzw. nematischen Phasen bilden kontinuierliche Reihen von cholesterischen Mischkristallen, während die festkristallinen Phasen bei allen Systemen einfache Eutektika aufweisen.

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Eight binary systems of a homologous series of cholesteryl esters (from cholesteryl propionate to cholesteryl decanoate) with trans-4-propylcyclohexyl-4-(trans-4-pentyl-cyclohexyl) benzoate (Licristal 1223, Merck, Darmstadt) were examined by thermomicroscopy and DSC analysis. In six cases induced smectic A phases with transition point maxima were observed. The cholesteric resp. nematic phases form continuous series of cholesteric mixed crystals, while the solid phases show simple eutectics.

     

Banana-shaped mesogens: effect of 2-methylresorcinol as the central unit on the mesomorphic properties of five-ring esters

Three homologous series of banana-shaped five-ring esters and one series of seven-ring esters derived from 2-methylresorcinol have been synthesized. This has been carried out to understand the effect of chemical structure on the mesomorphic properties of such compounds. It is shown that the 2-methyl substituent in the central phenyl ring destabilizes the mesophases when they are compared with those of the analogous unsubstituted compounds. Replacement of a phenyl ring by a biphenyl moiety (seven-ring esters) in the two arms of the bent-core molecule enhances the thermal range of the mesophases as well as the clearing temperatures. The mesophases have been characterized using techniques such as polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction, and by electro-optical investigations. In the 32 compounds investigated, two mesophases, B 1 and B 2 , have been identified.     

Synthesis and characterization of non-symmetrical liquid crystals containing a cholesteryl ester moiety

In this paper,a series of chiral non-symmetrical liquid crystals(nBA-chol)consisting of a cholesteryl ester moiety as chiral entity and a biphenyl aromatic core with different terminal alkyl chain has been synthesized and investigated for their liquid crystalline properties.Effects of numbers of methylene units in the terminal alkyl chain on the phase transition temperatures and on the temperature-dependent pitch lengths of the chiral liquid crystals have been studied.The long terminal alkyl chain tends ...     

Synthesis and properties of FeIII complexes with deuteroporphyrin and hematoporphyrin

Deuteroporphyrin and hematoporphyrin as complete methyl esters and their complexes with iron(III) were synthesized and characterized by NMR and electronic spectroscopy. For the first time the changes of the specific heat capacity of these solid biological objects with temperature were investigated by the method of differential scanning calorimetry. These parameters are shown to be smooth functions of temperature in the range 290–360 K, indicating the absence of the phase transitions in these systems.     

甾核基酯类化合物的合成与液晶性能

分别以胆固醇、胆酸为原料,合成了5种甾核基酯类化合物,采用红外光谱（FTIR）和紫外光谱（UV）对其结构进行表征,并用偏光显微镜（POM）和示差扫描量热法（DSC）研究其液晶行为。结果表明,合成的小分子产物丙酸胆固醇酯、苯甲酸胆固醇酯具有一定的液晶性能,而乳酸胆固醇酯和高分子的聚乳酸胆固醇酯、聚乳酸-胆酸共聚物在熔融状态下不具有液晶性质。     

Mesophases II

In the continuation of a review of the classification, properties and applications of mesophases, the general features of thermodynamic data of thermotropic liquid–crystalline phase transitions are surveyed. The orientation of molecules in liquid–crystalline mesophases is discussed in relation to the electrical properties. Some applications of mesophases are outlined. After surveys of both the structural classes of lyotropic mesophases and the properties of plastic crystals in cubic phases, the thermodynamic, structural and other properties of all mesophases-are summarily considered in relation to the present state of the knowledge in this field.     

Solidification-induced and shear-induced band texture in thermotropic liquid crystalline polymer films

Two phase diagrams of a six-ring double-swallow-tailed compound are presented where the mixing components involve electron-acceptor compounds. In the mixed phase region, nematic, smectic A and C, cubic and columnar phases are induced. In this way transitions between lamellar, cubic and columnar phases can be realized by variation of the con- centration. The mesophases occurring in these systems have been characterized by X-ray investigations.     

4-(5-Alkyl-2-pyridinyl)phenyl alkanoates: Some novel smectic materials for display devices

Abstract

Three homologous series of 4-(5-alkyl-2-pyridinyl)phenyl alkanoates have been prepared. The synthesis and the liquid crystal transition temperatures of these esters are reported. Many members of these three ester series exhibit enantiotropic, wide range smectic F mesophases and some narrow range smectic C mesophases. However, in admixture with a chiral smectic C base mixture, the esters often induce a substantial increase in the chiral smectic C–smectic A transition temperature and, at the same time, decrease the temperature of crystallization. Thus, the temperature range of the chiral smectic C mesophase is substantially extended at both high and low temperatures. Ordered smectic mesophases are only observed at very low temperatures, if at all. These chiral smectic C mixtures are characterized by short switching times in surface-stabilized ferroelectric liquid crystal displays (SSFLCD). These novel esters are of especial interest for short-pitch chiral smectic C mixtures for short pitch bistable ferroelectric liquid crystal displays (SBFLCD) with short response times.     

Effect of terminal perfluorocarbon chain containing mesogens on phase behaviors of chiral comb-like liquid crystalline polymers

A novel perfluorinated liquid crystal 4′-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoyloxy)biphenyl-4-yl undec-10-enoate (PFOBU) was synthesized, which exhibited smectic C phase. Several liquid crystalline polymers (PI–PVI) were synthesized by use of poly(methylhydrogeno)siloxane, PFOBU, and cholesteryl 3-(4-allyloxy-phenyl)-acryloate. The chemical structures and liquid crystalline (LC) properties of the monomers and polymers, and some ferroelectric properties of the chiral smectic C (S_C^*) phase were characterized by use of various experimental techniques. The effect of perfluorocarbon chains on phase behaviors of the fluorinated LC polysiloxanes was studied as well. PI and PII showed single chiral nematic (N^*) mesophase when they were heated and cooled, but PIII, PIV, PV, and PVI containing more perfluorocarbon chain units exhibited S_C^* phase besides N^* mesophase. Introduction of perfluorocarbon chain containing mesogens to the chiral cholesteryl-containing polymer systems resulted in a S_C^* mesophases, indicating that the fluorophobic effect could lead to microphase segregation and modifications of smectic mesophases from the chiral nematic phase.     

Polymorphism and mesomorphism of oligomeric surfactants: effect of the degree of oligomerization

A series of cationic oligomeric surfactants (quaternary dodecyldimethylammonium ions with two, three, or four chains connected by an ethylene spacer at the headgroup level, abbreviated as dimer, trimer, and tetramer) were synthesized and characterized. The influence of the degree of oligomerization on their polymorphic and mesomorphic properties was investigated by means of X-ray diffraction, polarizing optical microscopy, thermogravimetry, and differential scanning calorimetry. All compounds display layered arrangements with interdigitated dodecyl chains. The increase in the degree of oligomerization increases the interlayer distance and decreases the ordering in the solid phase; whereas the dimer sample is fully crystalline with well-developed 3D ordering and the trimer and tetramer crystallize as highly ordered crystal smectic phases. The number of thermal phase transitions and sequence of phases are markedly affected by the number of dodecyl chains. Anhydrous samples exhibit polymorphism and thermotropic mesomorphism of the smectic type, with the exception of the tetramer that displays only transitions at higher temperature associated with decomposition and melting. All hydrated compounds form lyotropic mesophases showing reversible phase transitions upon heating and cooling. The sequence of liquid-crystalline phases for the dimer, typical of concentrated ionic surfactant systems, comprises a hexagonal phase at lower temperatures and a smectic phase at higher temperatures. In contrast, the trimer and tetramer reveal textures of the hexagonal phase.     

Mesomorphic structure peculiarities of two mix-substituted phthalocyanines of the A3B type

Mesomorphic properties and structures of two mix-substituted lipophilic phthalocyanine derivatives of the A₃B type, with a different ratio of electron-donating (hexadecyloxy-) and electron-withdrawing (Cl-) substituents on the isoindol fragments ‘A’ and ‘B’, correspondingly, were studied by polarising optical microscopy, differential scanning calorimetry and small-angle X-ray scattering. Both compounds display columnar mesophases, and the type of organisation of the columns in the mesomorphic state was found to strongly depend on the number of peripheral chlorine substituents in the molecule. The di-chloro-substituted phthalocyanine forms a solid pasty lamellar phase at room temperature, which on heating undergoes successive transitions to two large-lattice columnar mesophases (2D-Col_h and 3D-M_Col) arising from the aggregation of several phthalocyanine-containing piles. On the contrary, aggregation of columns does not occur for the tetra-chloro-substituted phthalocyanine, which forms a nematic columnar mesophase of single phthalocyanine piles (1D-N_Col). While the di-chloro-compound partly crystallises on cooling, the nematic phase of the tetra-chloro-compound freezes at room temperature. The reasons for this different self-organisation behaviour are not yet fully understood, but some hints may be deduced from the proposed supramolecular models.