摘要:

We have studied the influence of surface state of aerosil on electro-optical characteristics of suspensions ‘aerosil-liquid crystal (LC)’. Modification of aerosil surface by hydrophobic fragments improves these characteristics. Also the dependence of a hydrophobic modificator structure on electro-optical characteristics was investigated. Explanation is given on the basis of the influence of the surface structure on the anchoring energy value of the LC-aerosil interface.

ISSN:1058-725X    

DOI:10.1080/10587259508033517

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We have studied the relationship between the UV irradiation time and electrooptical properties in the UV curable polymer dispersed liquid crystal (PDLC) film. Memory-type PDLC films are prepared with various terms of UV irradiation and the changes of transmittance, capacitance and resistance of the PDLC film are measured while the phase separation is advanced. The driving voltage increases in the PDLC film which is made with an insufficient or excessive UV irradiation. The memory transmittance also depends on the UV irradiation time.

ISSN:1058-725X    

DOI:10.1080/10587259508033518

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The ferroelectric liquid crystal molecule HOBACPC formes multilayers at the air-water interface. Measurements of the surface contact potential exhibit an orientation of those molecules adjacent to the liquid phase. Their polar head groups point towards the water. In contrast the molecules in the second and further layers are statistically oriented. The aminostilbazolium dye di5ASPBS serves as a probe molecule which is sensitive to the surrounding dielectric constant. We have inseted the dye in a HOBACPC matrix to examine the change of fluorescence during multilayer formation on the water surface. The fluorescence exhibits some characteristic features as a function of decreasing area: a strong decrease of the amplitude shortly before the formation of the first layer and several maxima at the following layer formations. The measurement at an area above 23 Å2/molecule is not reproducible due to domains larger than the measurement spot.

ISSN:1058-725X    

DOI:10.1080/10587259508033519

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Free-standing ferroelectric films in a rotating electric field have been investigated. The spontaneous formation and the evolution of dark and bright rings were studied by an image analysing system. Area and width of the rings depend on the extent of the ring system. A quasi-stationary state is possible which is characterized by a ring creation rate of zero and by a defined quantity of rings. The evolution of the systems is mainly determined by the elastic properties of the ferroelectric liquid crystals.

ISSN:1058-725X    

DOI:10.1080/10587259508033520

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

It has been reported that thin films of Poly-tetra-fluoro-ethylene (PTFE) deposited in a suitable manner will induce alignment in a liquid crystal1. These films are deposited in a one step dry process which offers advantages over polyimide or SiO2alignment layer application methods. Investigations of the effect of application conditions (pressure, temperature, deposition velocity) of this type of alignment layer on the quality of alignment in liquid crystals have been carried out. The surface pretilt angle induced in the liquid crystal by such an alignment layer has been measured and the PTFE films induce a low surface pretilt angle of the order of 1°. Some results of attempts to control this pretilt value by varying the conditions under which the alignment layer is deposited are presented. TN devices utilising PTFE alignment layers have been constructed and operating characteristics shown to be comparable to those for devices utilising commercially available polyimide alignment layers. There is a significant reduction in the threshold voltage of the PTFE aligned device as compared to that of a polyimide aligned device both having similiar slope characteristics.

ISSN:1058-725X    

DOI:10.1080/10587259508033521

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Amphotropic copolymers containing rod-like side groups combine the ability to form Langmuir-Blodgett multilayer assemblies with thermotropic liquid crystalline selforganization on temperature changes. Photochromic azobenzene side groups affect the supramolecular structure in such copolymers in dependence on irradiation wavelength and polarization of the incident light beam as well as temperature. The aggregation phenomena at the polymer air interface caused by the amphotropic properties of the material were reversibly modified by the light induced variation of the molecular shape of the photochromic moieties. The vertically layered structure had been destroyed and rebuilt upon irradiation and annealing the LB films. Moreover, the optical in-plane anisotropy was erased on irradiation and reinduced using linearly polarized light.

ISSN:1058-725X    

DOI:10.1080/10587259508033522

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

13C-NMR measurements of the chiral mesogen cholesteryl-undecylcarbonate (CHUC) adsorbed in Anopore membranes with cylindrical pores of 0.2μm diameter are presented. The pitch of CHUC in the cholesteric phase is of order of the pore diameter, and in view of the planar axial anchoring a strong influence of the walls on the director field can be expected.

ISSN:1058-725X    

DOI:10.1080/10587259508033523

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Insertion properties of Lasalocid and Monensin as sodium salts (LAS-Na, MON-Na) in model membranes of dipalmitoylphosphatidylcholine (DPPC) have been studied in two biomimetic buffered systems: monolayers (Langmuir Film Balance) and multilamellar bilayers (Differential Scanning Calorimetry). Effects varying with the concentration and with the surface pressure have been observed within the experimental range of molar ratios r = antibiotic/lipid from 0.005 to 0.1. The area occupied by each antibiotic molecule and the relative molecular area increase at a given pressure, are different for the two molecules. The calorimetric measurements result in concentration dependent modifications of the characteristics of the gel-liquid crystal phase transition in the case of LAS-Na. No such modifications are observed in the case of MON-Na.

ISSN:1058-725X    

DOI:10.1080/10587259508033524

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The thermal stability and structure of two uniform Langmuir - Blodgett films made of bipolar lipids from archaea have been studied. X-ray diffraction measurements at various temperatures from 20°C to 100°C were performed on these films, during heating and cooling cycles. The Bragg peak position, the integrated intensity and the peak width have been recorded as a function of temperature. Both intensity of diffraction peaks and layer thickness diminish at high temperatures while the correlation length, normal to the multilayer plane, displays some significant changes during the heating cycle. The data suggest the occurrence of some phase transitions. As a final result, the thermal stability of these two bipolar lipids LB-films is quite different and very high for the Phospho 2 LB film, which is stable till 100°C and is very promising for technological applications.

ISSN:1058-725X    

DOI:10.1080/10587259508033525

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The phase diagram of 4-(trans-4-pentyl-cyclohexyl)-benzonitrile, PCH-5, was obtained by DTA measurements up to a temperature of 370 K and up to pressures of 260 MPa. Dielectric studies on the static and complex permittivity have been performed on PCH-5 in the pressure range 0.1 – 140 MPa, the frequency range 1 kHz - 13 MHz and the temperature range 311 – 350 K. From the relaxation times in the nematic phase, τ∥we have calculated the activation volume, Δ*V∥of about 70 cm3/mol (decreasing with increasing temperature). and the activation enthalpy, δ‡Hρ, of approximately 70 kJ/mol. The pressure dependence of Δ*V∥is weaker than that found recently for 5CB. We have also calculated the (isochoric) activation energy of about 40 kJ/mol. The low-frequency relaxation process connected with molecular rotations about the short molecular axis was analysed in terms of the Martin-Meier-Saupe theory, yielding q = 10 kJ/mol for the nematic potential. The results are compared with recent high pressure results on 4-n-alkyl-4‘-cyanobi-phenyls.

ISSN:1058-725X    

DOI:10.1080/10587259508033526

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor