摘要:

A new family of chiral smectic liquid-crystalline compounds having a core structure of(Y ˭ C≡C or CH2CH2) have been synthesized and their thermal stabilities have been examined systematically in terms of influences of the linkage between the benzene ring and the pyridine ring, and the chain length of the terminal alkyl group.

ISSN:0267-8292    

DOI:10.1080/02678299008047396

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

On applying an appropriate electric field to a thin sample of ferroelectric liquid crystal a texture of long domains appears perpendicular to the smectic layers. We present observations showing that such treatment of the cell leads to its perfect bistability (i.e. a memory effect). The analysis of the equilibrium equations describing smectic liquid crystal elasticity shows how the director orientation is fixed both by a bulk deformation caused by the electric field treatment and by surface anchoring.

ISSN:0267-8292    

DOI:10.1080/02678299008047397

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

It is shown that molecules with tetrahedral symmetry can give smectic liquid-crystalline phases, both with liquid and with ordered layers. In contrast to the usual behaviour the layering is rather strong, leading to three orders in the X-ray diffraction pattern. A tentative model is given in which the long mesogenic substituents are bent at the spacers with which they are attached to the central carbon atom, such that in spite of the tetrahedral angles a rod-like shape is obtained.

ISSN:0267-8292    

DOI:10.1080/02678299008047398

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Several examples of liquid-crystalline carbohydrate derivatives incorporating a carbocyclic ring in the side chain are reported and the influence of structural variations discussed. The mesophase observed for all compounds described is smectic A and the mesophase stability is strongly affected by the linking unit between the carbocyclic and carbohydrate moieties.

ISSN:0267-8292    

DOI:10.1080/02678299008047399

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new type of chiral discotic liquid crystal is described. It is based on a triphenylene core but carries only one asymmetric side chain per mesogen. This system displays a columnar liquid-crystalline mesophase with a helical superstructure and a pitch of 3·0 nm over a temperature range of 227 K. Upon cooling it forms a glassy state. By broadband dielectric and2H NMR spectroscopy two motional processes are detected. The axial rotation of the discs around the column axis exhibits non-Arrhenius behaviour and is directly related to the glass transition. The second process is ascribed to localized side chain motions involving the ester linkages.

ISSN:0267-8292    

DOI:10.1080/02678299008047400

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor