摘要:

Recently a new family of flexible mesogens has been described namely hexa-alkylated derivatives of cyclotetraveratrylene. We have functionalized these compounds, obtaining monofunctionalized and bifunctionalized derivatives with heptyloxy side groups. A model dimer and polycondensates were synthesized. Calorimetric data as well as optical data prove that they exhibit columnar meso-phases. At this point it is not clear whether the conformation of the mesogenic units in the mesophase is tetragonal pyramidic with all of the mesogens being extended in one direction or discotic because of the high internal flexibility of the mesogenic core. The synthesis of the model dimer and the polycondensates as well as the calorimetric and optical data are the subject of this article.

ISSN:0267-8292    

DOI:10.1080/02678299008029199

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An investigation of the flexoelectric effect in a spatially inhomogeneous field revealed the two specific features of the liquid crystal optical response. First the optical response occurs at frequencies up to 500 Hz testifying to possible response time for flexoelectric effect-devices from 2 to 5 ms. Secondly in a photosensitive structure a flexoelectric effect application allows the implementation of an optical analogue of synchronous detection as well as the subtraction of images.

ISSN:0267-8292    

DOI:10.1080/02678299008029200

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The ferroelectric switching behaviour of the highly ordered smectic I* phase has been investigated in the mixture which shows a S*Iphase at room temperature. The bistability was obtained in a 3.5μm thick cell. Director switching and the reorientation processes have been studied by applying symmetric square and triangular wave pulses. It has been found that an asymmetric switching occurs in the smectic I* phase for low electric fields due to the hexagonal ordering of the molecules in the layer. This asymmetric switching was confirmed by optical microscopy and four stable states have been observed for low electric field. For higher electric fields only one state is stabilized which results in symmetric switching by both methods in the smectic I* phase.

ISSN:0267-8292    

DOI:10.1080/02678299008029201

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0267-8292    

DOI:10.1080/02678299008029202

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0267-8292    

DOI:10.1080/02678299008029188

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor