摘要:

Rheological property, shear stressvs.shear rate, of cholesteryl nonanoate (CN) is measured in a temperature region including the blue phases (BPs). From the measurement of the temperature dependence, an anomalous increase in the viscosity, accompanied by a non-Newtonian flow, is observed between 363.4 K and 367.5 K. The anomalous temperature region of 4.1 K obtained from the rheological measurement is wider than the BP region of 0.8 K determined from the thermal analysis, suggesting that the BP region is enlarged under an application of the steady shear flow.

ISSN:1058-725X    

DOI:10.1080/10587259808025378

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

N-(4-cyano-2-nitro-phenyl)[NCP]-L-serine has been synthesized from L-serine. Crystals of NCP-L-serine • DMSO complex having good optical quality were grown from solution. The crystal structure and the nonlinear optical properties were determined. Second harmonic generation (SHG) measurements according to powder method reveals that NCP-L-serine • DMSO complex possesses SHG activity.

ISSN:1058-725X    

DOI:10.1080/10587259808025379

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Polarized Fourier transform infrared (FTIR) and ultraviolet-visible (UV-VIS) spectroscopy were used to investigate the cause of liquid crystal alignment on polarized UV (PUV) irradiated polyimide (PI) films. PI films strongly absorb below 350 nm. PUV irradiation of the PI film caused a decrease in the intensity of the original IR absorbance peaks of the PI, due to degradation of the PI molecules, along with the appearance of a new peak at 3261 cm−1. Because the PI molecules oriented parallel to the direction of UV polarization preferentially degrade, the predominant orientation of the remaining PI molecules after PUV irradiation is perpendicular to the PUV polarization direction. Liquid crystal (LC) molecules align parallel to the predominant orientation of the PI and perpendicular to the PUV polarization direction.

ISSN:1058-725X    

DOI:10.1080/10587259808025380

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Some new triphenylene based chiral discotic liquid crystals have been prepared from readily available, naturally occurring amino acids and terpene. Triphenylene derivatives bearing one (3a-b,4a), three (2a) and six (1a-c) chiral chains have been synthesised and studied for their mesomorphic properties. Such materials may serve as excellent dopants to induce chiral phases. Induction of cholesteric phase in a nematic-discotic phase by doping with these chiral discotic LCs has been studied.

ISSN:1058-725X    

DOI:10.1080/10587259808025381

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To align liquid crystals on an alignment layer, the rubbing method is generally used. But it has some problems such as the generation of dust, and the difficulty of the quantitative control of rubbing intensity. To overcome these problems, we developed new photo-active mixture ofw-dye (see the Fig. 1(a)) and PVA which can be applied as an alignment material for liquid crystal display (LCD). Using this polymer, we made cells and observed properties of a photo-alignment layer and LC alignment. From these results, we discussed the mechanism of LC and polymer alignment by UV irradiation in photo-alignment layer. We show that this new alignment material may be used in commercial LCDs.

ISSN:1058-725X    

DOI:10.1080/10587259808025382

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The rubbed polyimide (PI) and PI LB films were fabricated and treated to align the nematic liquid crystal (LC) 5CB. The rubbed polyimide (PI) films aligned LC cell shows a higher LC pretilt angle than the cell aligned by PI LB films. Atomic force microscope (AFM) observations indicate that the rubbed PI films have a needle-like structure, while PI LB films have a groovy structure. We think that the needle-like structure plays a major role in producing the higher LC pretilt angle.

ISSN:1058-725X    

DOI:10.1080/10587259808025383

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Unidirectional liquid crystal (LC) alignment by a linearly polarized UV exposure was examined using various polyimides (PIs) which consist of different tetracarboxylic dianhydrides and diamines. Measurement of dichroic ratios of LC cells suggests that sensitivity of unidirectional LC alignment for UV dosage is largely affected by the chemical structures of PIs used. The results of dichroic ratio measurement of LC cells, UV absorption spectra, birefringences, FT-IR spectra of PI films, and molecular conformations of diamines in Pis calculations using molecular mechanics suggest that the selective photo-decomposition of PI caused the anisotropic van der Waals forces which aligns the LC along its optic axis in residual PI chain.

ISSN:1058-725X    

DOI:10.1080/10587259808025384

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Raman spectroscopy is used to investigate the degree of order found inin-situphotopoly-merised films exhibiting polarised emission. Studies indicate that the mixed system shows different degrees of order for its two molecular components. The degree of order was measured in the mesophase for the mixed monomers prior to polymerisation and was found to be in close agreement with the order of the two components measured in equivalent cured films. These studies have therefore provided an insight into the nature of molecular ordering in these mixed systems and shows that thein-situphotopolymerisation process does not greatly change the ordering in the system.

ISSN:1058-725X    

DOI:10.1080/10587259808025385

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Crystal and molecular structure of the compound 4-n-ethyl-4′-cyanobiphenyl (2CB), which exhibits nematic phase monotropically, is determined by direct methods from single crystal X-ray diffraction data. The crystal belongs to monoclinic system with space group P21, cell parameters beinga= 8.584(4),b= 5.865(3),c= 11.833(3) (Å) and β = 92.30(3)° with 2 molecules per unit cell. Refinement led toR= 0.079 withI> 2[sgrave](I). The molecules are in the most extended conformation. The phenyl rings are highly planar, the dihedral angle between them is 1.46°. Antiparallel pairs of 21symmetry related molecules are arranged in layers and the layers are stacked along [001]. The thickness of these layers is equal to the length of crystallographicc-axis. van der Waals' type of contact encompasses all the molecules within a layer. Molecular geometry and crystal packing are discussed in the context of geometry and packing of other knownnCB andnOCB structures.

ISSN:1058-725X    

DOI:10.1080/10587259808025386

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The surface tension-temperature characteristic of the homologous series 4,4′-di-n-alkanoyloxy-biphenyls (BP-n: CnH2n+1CO2-C6H4-C6H4-CO2CnH2n+1) has been investigated by using the computer-aided pendant drop method. In casen> 3 BP-n's are characterized by a highly ordered smectic G phase directly below the isotropic phase. Positive temperature coefficients of surface tension, which implies a surface-molecular excess order, are generally observed as the temperature is lowered to approach the phase transition. The remarkably wide temperature range of this anomaly is consistent with the suggestion that the existence of an underlying highly ordered phase favors the pretransitional surface ordering at the free surface of an isotropic phase.

ISSN:1058-725X    

DOI:10.1080/10587259808025387

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor