摘要:

Various kinds of polythiophene derivatives were synthesized and thermal properties were examined by DSC, polarized microscopic and X-ray diffraction observations. Fusibility and solubility of these polymers deeply depends upon the polymerization methods and polarity of the mesogenic group. Polymerization was carried out by oxidation and polycondensation methods. The polarity at the end of mesogenic group plays an important role for solubility and fusibility of the polymer in the case of oxidative polymerization. 3-Substituted polythiophene having polar group such as cyano or nitro at the end of mesogenic group was soluble in polar solvent and fusibility at higher temperature. The polymer having polar group at the end of mesogenic group prepared by mild polymerization condition such as polycondensation exhibited a clear smectic texture and also showed electrochemically active by cyclic voltamograms.

ISSN:1058-725X    

DOI:10.1080/10587259508033487

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A series of side-chain liquid crystal polymers have been screened for successhl deposition using the Langmuir Blodgett method. It was found that the best materials had glass transitions below room temperature. The behaviour of the spread film of one material was studied in detail using surface isotherms, surface potential, X-ray and neutron reflection techniques. It was found to undergo a phase transition from a thin, low density film to a thicker, more dense one as the surface pressure was increased. This corresponds to a reorientation of the mesogenic units so that about half of them point upwards. At higher pressure a transition to a multilayer occurs on the water surface. In the surface pressure range where deposition is possible, neutron reflection shows that the spread film has a stratum of close packed mesogenic units outermost and the total thickness (38 Å) agrees very well with the smectic layer spacing in the bulk. This similarity in structure could explain the ease of deposition.

ISSN:1058-725X    

DOI:10.1080/10587259508033488

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Effect of minor changes in chemical structure of main chain and mesogenic side chain on phase behaviour and spontaneous polarization, PS'of the polymer has been studied. Measurements of pyro- and piezoelectric effects and their relaxation are reported.

ISSN:1058-725X    

DOI:10.1080/10587259508033489

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

New mesomorphic chiral acrylates were synthesized. Their additions to a nematic liquid crystalline mixture cause the director of the nematogens molecules to adopt a helically twisted orientation. The pitch of the resulting helicoidal structure is determined by the concentration of the chiral dopant. Mesomorphic properties and actual pitches of several mixtures of these chiral dopants with nematic or cholesteric liquid crystalline solvents were studied. Photochemical polymerizations of these mixtures were performed in thin films which resulted in cross-linked polymer networks with a twisted superstructure. The use of such specific chiral additives in polymer stabilized cholesteric texture material resulted in white reflective displays. The electro-optical properties of such devices were investigated.

ISSN:1058-725X    

DOI:10.1080/10587259508033490

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Dielectric relaxation times and the static dielectric behaviour of monomers and oligomers with definite chemical structure are compared with each other.

ISSN:1058-725X    

DOI:10.1080/10587259508033491

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The dielectric properties of the liquid crystallline polymethacylates with side chain containing a terminal alkyloxy chain have been over wide ranges of frequency and temperature. The temperatures corresponding to the peak of the dielectric loss tangent for PM6BP and PM6BP5 in its temperature dependence agreed well with those phase transition. The activation energies at low temperature agreed with Δ-relaxation which is ε-relaxation by rotation of mesogenic gruop around the backbone chain. The dipole moment have been calculated by using the Frohlich modification of Onsager's equation. The alignment of both materials in the present of an a.c. electric field are also discussed.

ISSN:1058-725X    

DOI:10.1080/10587259508033492

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The real and imaginary parts of the optical transmittance and the relative permittivity have been measured for a polysiloxane ferroelectric liquid crystal polymer (FLCP) subjected to a weak alternating electric field. A simple dynamical model of the collective switching has been adopted for describing the director motion and the transport of ions through a FLCP cell. Numerical solution of a set of equations governing the director dynamics allows us to explain the transmittance and dielectric response of a FLCP cell. The model is shown to reproduce the experimental dielectric and optical transmittance response quite satisfactorily.

ISSN:1058-725X    

DOI:10.1080/10587259508033493

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In-situ photopolymerization of liquid-crystalline networks offers the opportunity to fix the molecular organisation of any LC phase in a thin plastic film. In addition to that, one has access to a number of additional techniques to affect the molecular organisation during or after the polymerization process which makes it possible to create odd molecular architectures in a controlled way. A number of these techniques are discussed in this paper.

ISSN:1058-725X    

DOI:10.1080/10587259508033494

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The measurements of the smectic reflection intensities of side-chain liquid-crystal polymers give access, after inverse Fourier transform, to the profile of coherent scattering length density along the normal to the layers. We give here three backbone density profiles associated to three liquid-crystal polymers: two polymethacrylates and one polyacrylate differing only by the nature of the backbone or by the mesogen extremity. It is shown that the backbones are always confined between the mesogen layers, and could be even localized right in the middle of the mesogen layer. In addition, this study demonstrates that small modifications of the liquid-crystal polymer formula are sufficient to induce very different backbone density profiles.

ISSN:1058-725X    

DOI:10.1080/10587259508033495

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The rate of domain growth in nematic side chain polymer samples is measured using the worm like path model for multiple scattering of light. The worm like path model which describes multiple scattaering in terms of the optical persistence length is found to apply both to multiple scattering in liquid crystal polymer films as well as to model polystyrene despersions. The required value of the optical persistence length can be calculated from the single scattering process so that there are no adjustable parameters in this model. The rate of domain growth in liquid crystal polymer samples is found to obey a scaling law where the growth exponent is about 0.85, contrary to the expected value of ½. In addition, an unexpected effect of the layer thickness on the rate of growth is observed, even for layer thickness much larger than the domain size.

ISSN:1058-725X    

DOI:10.1080/10587259508033496

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor