AbstractThe synthesis of two series of side-chain liquid crystalline polyoxetanes and polyoxiranes containing 4-alkanyloxybiphenyl-4′ -yl (2S,3S)-2-chloro-3-methylvalerate side groups is presented. Differential scanning calorimetry, polarizing optical microscopy, and X-ray diffractometry reveal smectic mesomorphism for all obtained polymers. Most of the prepared polyoxetanes present smectic A and chiral smectic C phases. The polyoxetane containing tweleve methylene units in the spacer is the only one showing two enantiotropic smectic A and B phases. All of the obtained polyoxiranes display two enantiotropic smectic A and B phases. Although the polyoxetane and polyoxirane backbones are more flexible than the polymethacrylate backbone, side-chain crystallization do not occur in any of the synthesized polymers.
A disk-like molecule, in which six α-linked terthiophenes are connected to a central benzene core via a thioether linkage, shows a sequence of calamitic liquid crystalline mesomorphism involving smectic C, smectic A and nematic phases.
Properties near the nematic-smectic-A-smectic-C multicritical point present in binary liquid-crystal mixtures are reviewed. Recent dynamic Fréedericksz deformation and quasielastic light-scattering results are described and their relationship with data from X-ray scattering and static light scattering is discussed.
ABSTRACTThe synthesis, characterization and phase transition studies of higher homologues of N(p-nbutoxybenzylidene)p-n-alkylanilines, Viz., 4O.m series (m=14 and 16) are carried out by thermal microscopy, differential scanning calorimetry and density. The compounds exhibit a phase variant of nematic and smectic-A. Density studies reveal a first order nature of IN transitions and a weak first order NA transitions. An estimate of pressure dependence of the phase transition temperatures using the volume and enthalpy data are presented. A comparison of these results with other reported results in nO.m and other compounds are presented.
ABSTRACTA low-molecular-weight liquid crystalline amphiphilic compound (Az6Bu) and a liquid crystalline polymethacrylate [P(Az6Bu)] with amphiphilic-mesogenic side-chains are reported in this present paper. A polyethyleneimine chain with 2-hydroxyethyl side-groups was used as the water-soluble spacer. Az6Bu exhibited a lyotropic columnar phase and no thermotropic mesophase. P(Az6Bu) showed thermotropic and lyotropic liquid crystalline properties. P(Az6Bu) formed thermotropic smectic A and C mesophases on the heating and cooling processes. The lyotropic systems consisting of P(Az6Bu) and water exhibited a smectic C lyomesophase with oilystreak and schlieren textures. The layered structures formed in the thermotropic and lyotropic mesophases are composed of a sublayer produced by the anisotropic alignment of aromatic-mesogenic groups and a sublayer of hydrophilic groups.
Anomalous solid structures formed by a thermotropic liquid crystalline polyimide (PI-LC) were investigated by thermal analysis, polarized light microscopy and x-ray analysis. It was revealed that PI-LC should undergo a phase transition from the crystalline to the isotropic phase through the smectic or nematic phase in the temperature range 277–300 °C. The PI-LC filament extruded at 280 °C, at which temperature the polymer was in liquid crystalline phase, was formed to have a structure similar to the smectic C phase, while that extruded and melt-drawn at 310 °C, at which temperature the polymer was in the isotropic phase, had a structure similar to the smectic A phase.
Two higher homologues of N(p-n-nonyloxybenzylidene)p-n-alkylanilines, viz. the 9O.m series with m = 12 and 16, are synthesised and characterised by thermal microscopy, differential scanning calorimetry and density studies. The compounds exhibit the phase variants smectic-A, smectic-B and smectic-G. Density studies reveal the first order nature of the isotropic to smectic-A and smectic-A to smectic-B transitions. An estimate of the pressure dependence of the phase transition temperature, using volume and enthalpy data, is presented. A comparison of these results with those reported on nO.m and other liquid crystalline compounds is presented.
Hexakis(terthiophenylthio)benzene as a Mew Class Liquid Crystalline Molecule