摘要:

Infrared reflection absorption spectroscopy (IRAS) was used to study the molecular alignment of the ferroelectric liquid crystal material, (S)-4-(α-methylheptyloxy)-4′-(4″-n-octylphenyl-oxycarbonyl)biphenyl (MHOPOB), on a highly-purity polyvinylalcohol (PVA) film. The molecular alignment was characterized as a function of the temperature and the thickness of the liquid crystal. For the film of 200nm in thickness, the molecules in the chiral smectic C phase (SmC*) were aligned with their long axes perpendicular rather than parallel with respect to the PVA substrate surface. This alignment was found to disappear at the isotropic phase temperature. A similar molecular alignment was observed for a 20nm-thick MHOPOB film in the SmC* phase, but the detailed alignment was different from that in the 200nm-thick film. This alignment in the SmC* phase was sustained even at the isotropic temperature in contrast to the 200nm-thick film, suggesting a short-range interaction between the PVA film surface and MHOPOB molecules. An experimental support for this short-range interaction is furnished by our polarization modulation IRAS measurements. The effect of PVA rubbing on the alignment is also discussed.

ISSN:1058-725X    

DOI:10.1080/10587259508037296

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The solid state chemistry of bis(dimethylamino) polymethine salts (n = 1,2,3,4) was investigated using thermogravimetry, difference thermal analysis, mass spectroscopy, UV/VIS spectroscopy and HPLC to analyze the extruded gaseous products and the residue.

ISSN:1058-725X    

DOI:10.1080/10587259508037297

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We have studied the static electricity and optical retardation generated by rubbing the surfaces of polyimide (PI) and polyamide (PA) films. The static electricity increases with the Rubbing Strength (RS) and varies with the different PI films.

ISSN:1058-725X    

DOI:10.1080/10587259508037298

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Highly-conjugated main chain polymers have been studied extensively in recent years as third order non-linear optical materials. However, in a non-centrosyinmetric system such as a polyene which has been substituted with an electron donor and acceptor group, the relaxation of certain selection rules results in an increase in the static third order hyperpolarisibility. Consequently, there has been recent interest in the third order non-linear optical properties of materials more typically studied for their quardratic non-linear response. One of the driving forces for this work has been the possibility of producing single device substrates possessing significant second and third order non-linearitics which could lead to highly integrated optical devices.

ISSN:1058-725X    

DOI:10.1080/10587259508037299

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A new series of chiral materials, hexyl(2s)-2-(6-(-4-(4′-alkoxyphenyl)benzoyloxy)-2′-naphthyl)propionates (HmPBNP;m= 6-18) had been prepared and their liquid crystalline properties were investigated as a function of alkyl chain length. These chiral materials exhibited novel ferroelectric Sc* and antiferroelectric ScA* phases and a propensity to the formation of the ScA* phase was found at longer alkyl chain lengths (m= 10, 12 - 18). An odd-even effect of the threshold voltage as a function of alkyl chain length for compounds HmPBNP (m= 12-16) possessing antiferroelectricity was observed. Spontaneous polarization and transverse dipole moment were also measured and are discussed in terms of the elongated alkyl chain length.

ISSN:1058-725X    

DOI:10.1080/10587259508037300

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A simple model for the one-dimensional nematic director configuration is used for a qualitative description of orientation dynamics in a nematic layer with a surface viscosity. This parameter may appear in dependencies of transient times on the layer thickness. The approximate formulae for both the decay and rise times are derived.

ISSN:1058-725X    

DOI:10.1080/10587259508037301

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Two- or three-ring compounds having 1,2,3-trifluorophenyl substituent (3F-compounds) were synthesized and their physical properties were measured to evaluate the applications to active matrix liquid crystal displays(AM-LCDs). The 3F-compounds gave good physical properties for AM-LCDs and, in particular, an excellent voltage-holding ratio (VHR), comparable to the compounds having 1,2-difluorophenyl substituents (2F-compound) which are currently used for AM-LCDs. The important point is that 3F-compounds showed much lower threshold voltage (V10) than 2F-compounds. It was demonstrated that one mixture of 3F-compounds with 2F-compounds gaveV10of about 1.30V at 5.5μm-cell gap. From these results, it was concluded that the 3F-compounds are excellent liquid crystalline materials for AM-LCDs with a low-voltage IC driver, for example the 3V IC driver.

ISSN:1058-725X    

DOI:10.1080/10587259508037302

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We have studied the electroconvective behaviour of MBBA, with initial homeotropic boundary conditions, employing a.c. fields acting transversely to the line of sight. Two major types of convective structure occur. They may be described as the distorted-homeotropic (VD) and distorted-planar (HD) states. The first bifurcation is to theVDstate and takes place at a threshold voltage which varies parabolically with the electrode-separation. The second bifurcation corresponds toVD-HDtransformation occurring close to turbulence. TheHDstructure, once nucleated, propagates in a highly organized and coherently winding manner so that an array of + 1 linear defects form at the axes of circulation. The growth speed ofHDfront is strongly voltage dependent. Field induced undulatory structures develop along theV-Hinterface below the threshold of electroconvection.

ISSN:1058-725X    

DOI:10.1080/10587259508037303

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

X-ray diffraction studies of four alkoxy cyanobiphenyls (alkyl = nonyl, decyl, undecyl and dodecyl) have been undertaken to determine orientational order parameters, layer thickness, packing fraction and coefficients of HJL type potential. All these values show some odd-even effect with the number of chain carbon atoms. Powder X-ray patterns from these compounds in solid phase have also been indexed satisfactorily. Orientational order parameters have been fitted to those calculated from McMillan's theory by varying the parameters a and σ.

ISSN:1058-725X    

DOI:10.1080/10587259508037304

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Guided optical waves are very sensitive to the alteration of optical properties of dielectric media. In this report, we demonstrate the use of guided waves for studying dynamic behavior of ferroelectric liquid crystals. Propagating light in the anisotropic medium suffers a birefringent effect, which causes coupling ofp- ands-polarized light. Theoretical calculations, based on the Maxwell equations, successfully describe this phenomena, using a dielectric tensor diagonal in molecular coordinates, which is transformed to the laboratory coordinate system by three Euler angles. The waveguide measurements are able to probe the molecular orientation and movement of the liquid crystal molecules in the three dimensional coordinate system. This method has been used to examine the switching behavior in the SmC* phase. The bistable states and the path of the molecular swing under alternating external electric fields are well characterized by the reflected intensity of single and double frequency modulation.

ISSN:1058-725X    

DOI:10.1080/10587259508037305

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor