摘要:

The principle of magnetic levitation is demonstrated using a large magnetic field gradient to elevate a polycrystalline sample of dodecyloxycyanobiphenyl against gravity. Additionally, a nematic droplet of pentylcyanobiphenyl clinging to a vertically oriented wire is elevated against gravity. The contact angle and length of the droplet are extracted from the droplet shape in the context of a gravitation-free model.

ISSN:0267-8292    

DOI:10.1080/026782997208145

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Three classes of 4-pyridone (1H-pyridin-4-one) terminated liquid crystals were synthesized and their mesogenic properties examined. These liquid crystal classes differ in the composition of the aromatic core group which vary among azobenzene, stilbene or tolane groups. The synthesis of the 4-pyridones was accomplished by aromatic nucleophilic substitution reaction of the appropriate activated aryl fluoride with 4-hydroxypyridine. These pyridone liquid crystals possess broad enantiotropic nematic and smectic A phases and may possess useful properties such as high birefringence and polarity including hydrogen bonding capability. The original report of a 4-pyridone containing liquid crystal due to Vorlander has been substantiated.

ISSN:0267-8292    

DOI:10.1080/026782997208154

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper the relationship between tensorial and vector approaches for elastodynamics is examined in the framework of continuum theory of nematics. It will be elucidated that the Lagrange multipliers are required in the tensorial framework as well as the vector framework to assure equivalence between them. A contraction for the tensorial indices in the the time- dependent Ginzburg-Landau equation will be found eventually to result in the vector form concerned with the Ericksen-Leslie equation without flow dynamics.

ISSN:0267-8292    

DOI:10.1080/026782997208163

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The formation of a re-entrant columnar discotic hexagonal ordered phase (re-entrant Col ho phase) is reported for the asymmetrically substituted triphenylene 3,6,7,10,11-penta- pentyloxytriphenylene-2-yl pivaloate (pivaloate) and its structural and dynamic properties described. The re-entrant phase behaviour is strongly modified by doping the pivaloate with the electron acceptor 2,4,7-trinitrofluorenone (TNF).

ISSN:0267-8292    

DOI:10.1080/026782997208172

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The synthesis and mesomorphic properties of a variety of polyfluorinated alkylaryl-ethanes and-ethenes are reported. The number and position of the symmetrically disposed fluorosubstituents has been varied from six to four and the mesomorphic properties of the compounds are compared with those of the analogous octafluoro-substituted compounds previously reported. All the compounds are moderately low melting, mesomorphic and the type of mesophase formed is dependent upon the number and position of the fluoro- substituents. Increasing the number of fluoro-substituents from four, to six and to eight in a series of polyfluoro-alkylarylethanes decreases the mesophase thermal stability in a stepwise manner and eliminates smectic properties whilst retaining the nematic phase.

ISSN:0267-8292    

DOI:10.1080/026782997208181

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

One cause of the hysteresis in the voltage-transmittance curve is polarization in the alignment layers brought about by the spontaneous polarization of FLC molecules. The hysteresis was reduced by increasing the conductivity of the alignment layers. The structural changes on switching were examined by measuring time-resolved shifts of FT-IR peaks of selected groups. The shifts of selected groups in the IR peak can be attributed to changes in the local dielectric constants of the ambient environment during switching by molecular orbital calculations. The orientation on switching in the SmC* phase was found to be similar to that in the N* phase.

ISSN:0267-8292    

DOI:10.1080/026782997208190

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

4-n-Nonyl-4′-cyanobiphenyl, C22H27N,Mr= 305.45, triclinic,P1,a=9.765(1)Å,b= 11.460(2)Å,c=17.860(2)Å, α=85.460(2), β=80.870(1), γ=71.630(1),V=1871.9(3)Å3,Z= 4,Dm=1.079M g-3,Dc= 1.084 M g-3, μ=0.463 mm-1,F(000)=664, lambda (CuKα)=1.5418Å, finalRandwR2 are 0.0523 and 0.1559, respectively.

ISSN:0267-8292    

DOI:10.1080/026782997208208

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The syntheses and structural properties of four liquid crystalline monomers are presented. They were prepared by two different reaction pathways. Transition temperatures and phase characterization were done by DSC, polarization microscopy and X-ray diffractometry. The dependence of phase transition temperatures on substitution of the aromatic core are discussed. Two of the compounds investigated highly ordered smectic phases. The improvement of the conjugation by means of a lateral hydroxy group disturbs the occurrence of the E re-entrant phase with smectic-like fluctuations of the C-type was observed in a compound with a lateral hydroxy group. The existence of this re-entrant nematic phase was confirmed by X-ray measurements both on cooling and heating of the sample. the alkyl chain lengths and the lateral show and B phases. The presence of a nematic

ISSN:0267-8292    

DOI:10.1080/026782997208217

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Columnar discotics were used as the hole transporting layer in single layer, two layer and three layer light emitting diodes because of the unusually large hole mobility of such materials. The observations are that the onset fields are small compared with most devices using nondiscotic hole transporting layers, that these values are strongly reduced with increasing number of layers, that the orientation of the columns along the layer film normal causes a further decrease of the onset voltage and finally that the quantum efficiencies increase significantly as the number of layers is increased.

ISSN:0267-8292    

DOI:10.1080/026782997208226

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor