摘要:

Liquid crystal-polymer composites containing a low proportion of polymer are of interest because of their low driving voltage, but they can show anomalous electro-optical curves, such as a minimum in the electro-optical curve. We explain the existence of this minimum, by a partial orientation of liquid crystal domains, together with the presence of mobile polymer fragments. This partial orientation is visible using a polarizing microscope, and the presence of polymer that is not linked to the main network is proved by size exclusion chromatography of the liquid crystal extracted from the composite.

ISSN:0267-8292    

DOI:10.1080/02678299408037342

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The phase behaviour of a mixed dispersion of dioleoyl derivatives of phosphatidylethanolamine and phosphatidylcholine (3:1, by weight) in an excess of water was compared with that in 1·8 M trehalose using dynamic X-ray diffraction, differential scanning calorimetry and freeze-fracture electron microscopy. The phase transitions of the fully-hydrated dispersion observed upon heating, proceeded with lamellar-gel→lamellar liquid crystalline→inverse cubic→inverse hexagonal phase at temperatures of −10°C, 49°C, and 67°C, respectively. Our results confirm the existence of an inverse cubic phase of this system and support the model mechanism for the lamellar/non-lamellar phase transition previously suggested by Siegel (1986,Biophys. J.49, 1155, 1171). Dispersion of the binary lipid mixture in a 1·8 M solution of the naturally occurring cryoprotective disaccharide, trehalose, inhibited the formation of both lamellar liquid crystalline and inverse cubic phases and resulted in a direct transition from lamellar-gel to inverse hexagonal phase at about −6°C. The effect of trehalose is discussed in terms of a ‘water replacement’ model and Hofmeister effects on water structure. Trehalose is regarded as a kosmotropic agent that may also interact directly with the lipid polar groups. Comparison of the relationship between temperature and the dimensions of the inverse hexagonal phase formed in the presence and absence of trehalose suggests that the osmotic effect of the impermeant trehalose prevents water molecules from being taken up by the hexagonal mesophase which is normally more hydrated that the lamellar phase.

ISSN:0267-8292    

DOI:10.1080/02678299408037343

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A series of new optically active δ-lactones were synthesized as chiral dopants for ferroelectric liquid crystals (FLCs). The response time of an FLC mixture containing 4 mol% (S)-2,2-dimethyl-5-[2-fluoro-4-(5-n-octylpyrimidin-2-yl)-phenoxy[methyl-δ-valerolactone was 25 μs at 25°C. (0–90 per cent change in light transmission, 10 V μm−1). The synthesis and properties of these materials as practical chiral dopants are reported.

ISSN:0267-8292    

DOI:10.1080/02678299408037344

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A relationship between the electro-optic switching time and dielectric parameters of a S*cferroelectric liquid crystal (FLC) is obtained. This relationship is derived in terms of spontaneous polarizationPs, relaxation time τGand dielectric strength ΔεGof the Goldstone mode. It shows clearly that the switching phenomenon in FLCs is governed by the dielectric behaviour of the Goldstone mode. Based on the Landau model, the switching time has also been related to the material parameters of the FLC.

ISSN:0267-8292    

DOI:10.1080/02678299408037345

出版商:Taylor & Francis Group    

年代:1994

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:10.1080/02678299408037331

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor