摘要:

Amorphous highly twisted nematic liquid crystal display devices have been prepared by a nonrubbing technique. The liquid crystals are injected into the cells in the isotropic phase and then cooled down to the nematic phase. Micro-domains of highly twisted nematic liquid crystals are formed during the cooling process. The twist angles of the micro-domains are controlled by the concentration of the chrial dopants. The transmission spectrum and the electro-optical characteristics of the devices have been measured. The experimental results show that the devices possess wide and uniform viewing angle characteristics (−51 to +52/ −49 to +48 degrees). The 4 × 4 optical matrix method has been applied to a model of randomly distributed multi-domains of highly twisted nematic liquid crystats. The theoretical results are in good agreement with the experiment.

ISSN:1058-725X    

DOI:10.1080/10587259508031009

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Long chain substituted phthalocyanines are increasingly of interest because of their high solubility in common organic solvents and their liquid crystalline properties. 2,3,9,10,16,17,23,24-Octakis(decyloxy)phthalocyaninatonickel(II) (1), -palladium(II) (2) and -platinum(II) (3) were synthesized by reacting 1,2-dicyano-4,5-bis(decyloxy)benzene with the corresponding metal(II) salts and their liquid crystalline properties were investigated. Similarly, 1,4,8,11,15,18,22,25- (4) and 2,3,9,10,16,17,23,24-octakis(heptyl)phthalocyaninatonickel(II) (5) were prepared and their properties were compared. Compound 4 was investigated in detail with respect to its electrochemical properties.

ISSN:1058-725X    

DOI:10.1080/10587259508031010

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The self-diffusion coefficients of nematic liquid crystals p-n-heptyloxybenzoic acid and p-n-nonyloxybenzoic acid have been measured depending on the temperature. The influence of the process of dimer formation on the self-diffusion was shown.

ISSN:1058-725X    

DOI:10.1080/10587259508031011

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Insertion properties of the antibiotics Lasalocid and Monensin sodium salts (LAS-Na and MON-Na) in Langmuir monolayers of two different lipid molecules, dipalmitoylphosphatidylcholine (DPPC) and octadecanol (C180H), have been investigated. Results from compression isotherms of the films on pure water and on a biologically buffered subphase have been compared. Values of the molecular areas of mixed films of antibiotic/lipid and of the molecular areas of the pure lipids, at a given surface pressure, have been used to calculate the aggregation numberkof the solute molecules in a concentration range of ρ (moles of antibiotic/moles of lipid) from 0.005 to 0.1. Theknumber in the film of DPPC increases when ρ increases, it is enhanced on the buffered subphase compared to the subphase of water and it is more important for MON-Na than for LAS-Na. There is hardly any evidence ofaggregation in the films of C180H. The two lipid systems both have in common that the mixed films with LAS-Na on the buffered subphase are the most pressure resistant and the ones from which the antibiotic is the least easily expelled.

ISSN:1058-725X    

DOI:10.1080/10587259508031012

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A statistical-mechanical theory which takes into account translational-translational, orientational-orientational and mixed correlations based upon the method of conditional distribution functions is applied to calculations of the order parameters and the rotational viscosity coefficient (RVC) of a system composed of interacting ellipsoidal molecules near an interacting wall. The calculations have been carried out for cubic close packing with the nearest-neighbor Gay-Berne intermolecular potential and with a (9–3) like orientation-dependent molecule-wall interaction. The theory shows that the number of surface layers which must be taken into account depends more on the character of intercell correlations in the system than on the direct wall-nematic interaction. The equilibrium order parameters and rotational viscosity coefficient at the solid-nematic fluid interface have been calculated.

ISSN:1058-725X    

DOI:10.1080/10587259508031013

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We report the measurement of electric conductivity in two cyanobiphenyls 7CB and 8CB. The alignment has been achieved using an electric field. We report that for 7CB the anisotropy in conductivity is positive at all temperatures. For 8CB too, we find that Δσ is positive both in the nematic and the smectic phase. This is in sharp contradiction with what has been found in most smectics and particularly with the work of Jadzyn and Kedziora5for 8CB.

ISSN:1058-725X    

DOI:10.1080/10587259508031014

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this paper, experimental investigations are reported on the unwinding process of a planar long pitch S*Cphase under DC and AC electric fields. The investigations are carried out ona cell with a spacing of 50μm. The DC critical fields (Edc) for unwinding the helical texture are measured at different temperatures. Three patterns of electrohydrodynamic instabilities are found to exist under AC electric fields.

ISSN:1058-725X    

DOI:10.1080/10587259508031015

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Solid state structure has been studied for a series of recently synthesized liquid crystalline polycarbonates1based on methyl-substituted stilbene mesogen and methylene-containing flexible spacer. These polymers are referred to as HMS-n, wherenis the number of methylenes in the flexible spacer group. The stability of the liquid crystalline phase and its relationship to the three dimensional crystalline phase were studied. X-ray diffraction patterns of raw fibers drawn from the mesophase revealed that the stability of the mesophase decreases as the methylene spacer length gets close to that of mesogen. From X-ray diffraction patterns of annealed fibers and molecular modeling studies, the unit cell parameters of HMS-5 to 8 were determined. HMS-5 and 6 have an orthorhombic structure while HMS-7 and 8 have a monoclinic structure. More important, an odd-even oscillation is observed in thed-spacings of the (020) and (110) reflections as a function ofn, which relates to differences in interchain packing in the odd and even members of the series. All HMS-5 to 8 have a stable intermeshed crystal structure in which the mesogen and the flexible spacer group on adjacent chains are aligned. In this structure, the disposition of the carbonate group differs fromn-even ton-odd, and is responsible for the odd-even effect seen in the two dominant interchaind-spacings. We suggest the higher degree of overlap of the carbonate linkage of HMS-7 and 8 might be the reason for their less stable mesophase compared with HMS-5 and 6.

ISSN:1058-725X    

DOI:10.1080/10587259508031016

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Rubbing-induced molecular aligement on an alkyl-branched polyimide film with varying unidirectional rubbing strength has been investigated with the use of optical phase retardation measurement, atomic force microscopy (AFM), and second-harmonic generation (SHG). Our AFM images suggest that the rubbing- induced micro-groove should play a minor role in aligning liquid crystal (LC) molecules. The polar angle of the polar head group of a LC monolayer on an alkyl-branched polyimide film was found to vary with the rubbing strength. The results obtained from various experimental techniques can be reconciled with a simple molecular model proposed in this paper.

ISSN:1058-725X    

DOI:10.1080/10587259508031017

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Alignment of nematic (7CB)and ferroelectric (CS 1013) liquid crystals on rubbed polyaniline films has been investigated. It was found that polyaniline serves as an excellent template for the alignment of both nematic and ferroelectric liquid crystal molecules. Polyaniline also acts as a conducting surface under the conditions of preparation.

ISSN:1058-725X    

DOI:10.1080/10587259508031018

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor