摘要:

The synthesis of novel liquid-crystalline heteroaromatic compounds incorporating the five membered thiophene and furan rings is described. The objective of the present work is to substitute the mesogenic units styrylthiophene, styrylfuran, phenylthiophene and phenylfuran for the aromatic structural units styrylbenzene and biphenyl in known mesomorphic compounds, thereby permitting a comparison of the effect of heterocyclic units on mesomorphic properties. The compounds synthesized with the mesogenic units styrylthiophene and phenylthiophene exhibited liquid-crystalline properties while compounds with the units styrylfuran and phenylfuran did not. The existence of mesophases in these compounds is closely associated with the configuration (linearity) of the molecule. The heterocyclic rings thiophene and furan are pentagonal and 2,5-disubstitution leads to non-collinear bonds which produce a deviation from linearity of the order of 32° and 54°, respectively.

ISSN:0267-8292    

DOI:10.1080/02678299308029058

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An analysis of the permitted structures for a cholesteric liquid crystal based on the continuum theory as a function of the anchoring conditions and the thickness of the liquid crystal layer is presented. A new type of bistability is found. The stability domains of various structure types are given.

ISSN:0267-8292    

DOI:10.1080/02678299308029059

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The thermodynamics of the SA‒N phase transition has been studied within the framework of the McMillan model generalized to biaxial molecules. The influence of the biaxiality of the molecular pseudopotential has been shown to be weak for the transition temperatureTSAN, noticeable for the tricritical point positionTSAN. on the line of SA‒N transitions and strong for the entropy of the transition ΔSSAN. With the McMillan parameters α and δ being constant the entropy change ΔSSANdecreases with increasing biaxiality parameter λ For sufficiently high values of δ and for α corresponding to a narrow nematic range increasing λ can result in changing the SA‒N transition from first to second order. The influence of λ on the change of the biaxialityG=Sxx—Syyof the molecular order parameter in the smectic phase is in agreement with available experimental data.

ISSN:0267-8292    

DOI:10.1080/02678299308029060

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Fluoro and non-fluoro polymer alignment layers of high and low pre-tilt angle were developed for ferroelectric liquid crystal display devices to exploit the effect of rubbed polyimide, polyamide-imide and polyamide alignment layers on pre-tilt angle and other electro-optical properties. Fluorine containing polyimide and polyamide alignment control layers displayed high pre-tilt angle (< 10°) and good alignment of liquid crystal molecules with no zig-zag defects by means of standard rubbing techniques. Non-fluoro polymer alignment layers showed relatively small pre-tilt angle (< 5°) with good or random alignment having some zig-zag defects in the ferroelectric liquid crystal cells. The ferroelectric liquid crystal used in the experiment was CS-1011 having the phase sequences SC*-SA-N*-I. The characteristic changes due to structurally different polymer layers on ferroelectric liquid crystal alignment are described.

ISSN:0267-8292    

DOI:10.1080/02678299308029061

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We present scanning tunnelling microscopy images of a ferroelectric liquid crystal in its chiral smectic C phase. These images show evidence of pronounced interaction between the adjacent lateral dipoles located near the chiral centres of neighbouring molecules. The two dimensional structure at the graphite—liquid crystal interface is found to be highly ordered. Features of this crystal-like order are the pronounced dimer arrangement within a layer and a kinked conformation in which the aromatic core is tilted with respect to the chains. The core axis is tilted at 30° with respect to the layer normal in the plane of the interface. This tilt is very similar to the tilt angle of the bulk material.

ISSN:0267-8292    

DOI:10.1080/02678299308029062

出版商:Taylor & Francis Group    

年代:1993

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:10.1080/02678299308029047

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor