Papers by Keyword: Smectic A

Abstract: A series of new rod-shaped liquid crystal, 6-methoxy-2-(4-alkyloxybenzylidenamino) benzothiazoles possessingeven numbers of carbon atoms at the alkyloxy chain (C_nH_2n+1O-, n = 10, 12, 14, 16, 18) are prepared and characterized. The phase behaviour of these new compounds was studied by differential scanning calorimetry and polarising optical microscopy. All members exhibited mesophase. Influence of alkyl chain length on the mesomorphic properties was studied. Enantiotropic nematic phase was identified in all the members except for n = 18. Lower member (n = 10) exhibited monotropic (metastable) smectic A phase. The enantiotropic smectic A phase was observed from n-dodecyloxy derivatives onward to the last homologous synthesized.

Abstract: 1,4-butylene bi-p-hydroxybenzoate (BBHB) was synthesized using methyl p-hydroxyl- benzoate and 1,4-butanediol under catalyst and stabilizer conditions; Then, the thermotropic main- chain liquid crystalline polysiloxanes (MCLCPs) with flexible spacer, were synthesized using BBHB and dimethyldiethoxysilane reagents by melting polycondensation. The chemical structures and properties were characterized by FT-IR, polarized optical microscopy (POM) and differential scanning calorimeter (DSC) respectively. It was found that MCLCPs was the type of smectic A liquid crystal, and the liquid crystal temperature ranged from 58°C to 143°C, i.e. its variationrange reached 85°C. In addition, the polysiloxane was used as the flexible main-chain and the flexible chains CH₂ was embedded into the rigid structural blocks of liquid crystalline polymers, which not only decreased the melting point below the thermal decomposition temperature, but also made the clearing point and a stable liquid crystal state observed.

Abstract: A Landau-de Gennes type model for the direct isotropic/smectic A phase transition is used to study surface-enhanced smectic ordering in the stable smectic temperature regime. A unified surface-free energy functional is proposed which can be utilized for homeotropic and planar surface anchoring. The time-dependent complex Landau-Ginzburg evolution equations and boundary conditions are derived for thin-film geometry. Simulation results are presented for the two types of anchoring and compared to observations from experiments and previous simulations. Simple visualization software for smectic layering was developed and is also presented that is compatible with discretized numerical solutions of the model.