摘要:

Three acrylate side-chain polymers in which the mesogenic moieties are based on the 4-n-alkoxyphenyl-4′-(4″-methylhexyloxy) benzoates have been characterized by differential scanning calorimetry, optical microscopy and X-ray diffraction. For shorter flexible spacers (n = 2) both smectic A and C*phases are observed thus making this polymer interesting for the fabrication of electro-optical devices based on ferroelectric properties (a smectic A phase is required for alignment purposes). For longer flexible spacers,(n= 6, 11) only the smectic A phase remains.

ISSN:0267-8292    

DOI:10.1080/02678298608086664

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Liquid-crystalline side group copolymers containing dyes can be macroscopic-ally oriented and the orientation can be locked-in below the glass transition temperature. The order parameters of anthraquinone dyes and a trisazo dye in nematic and smectic glasses were determined by optical absorption measurements. The dyes have higher degrees of order in the smectic glass than in the nematic glass. A comparison of order parameters of covalently bonded dyes with order parameters of monomeric dyes dissolved in the corresponding homopolymers demonstrates the influence of covalently anchoring the dye to the polymer.

ISSN:0267-8292    

DOI:10.1080/02678298608086665

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A smectic B (S,) solvent may provide a very highly ordered, and possibly oriented, host medium for polymerization processes. Photochemical polymerizations of two bisacrylic monomers were therefore carried out in a SBmedium. The process conditions were chosen on the basis of a preliminary study of the monomer-solvent binary system carried out by differential scanning calorimetry (D.S.C.), optical microscopy and X-ray diffraction. The polymerization was then studied by D.S.C. at different reaction times. These measurements showed clearly that there is a point along the reaction path at which the growing polymer chains start segregating from the solvent and the mesomorphic bulk no longer acts as a reaction solvent but only as a reservoir for the ponomer. The polymer chains from that point keep growing only upon or between the faces of the SBlayers. Electron microscopy observations showed that the morphology of the final polymer is affected by this interlayer process.

ISSN:0267-8292    

DOI:10.1080/02678298608086666

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

An expression for the entropy as a power series in the order parameter is derived in the context of molecular field theory. The expression is valid both at and away from equilibrium. It is a unique generalization of molecular field theory to non-equilibrium situations. Discrepancies with certain expressions which have appeared in the literature are resolved. Analysis of the radius of convergence of the power series indicates that in certain cases, including the Maier-Saupe model of liquid crystals, molecular field theory and Landau theory cannot be made to agree over the entire range of possible values of the order parameter.

ISSN:0267-8292    

DOI:10.1080/02678298608086667

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Many alkyl derivatives of carbohydrates are used as detergents for cell wall membranes. This study describes the liquid-crystalline properties of a number of these systems. The combination of a hydrophilic carbohydrate moiety and a hydrophobic aliphatic substituent leads to the formation of both thermotropic and lyotropic liquid-crystal mesophases. Materials with this structural combination are suspected to form interdigitated bilayer smectic A phases. The central core region of the layer is held together by dynamic hydrogen-bonding between the neighbouring carbohydrate moieties, whereas the terminal aliphatic chains create fluidity between layers.

ISSN:0267-8292    

DOI:10.1080/02678298608086668

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The19F N.M.R. spectrum of 1,2,2,2-tetrachloro-l,l-difluoroethane has been studied in the nematic liquid crystal ZLI1167 (Merck) upon rotation at the magic angle. The director of the liquid crystal is oriented perpendicular to the spinning axis when the angle between the rotation axis and the magnetic field is less than the magic angle and parallel when this angle is more than the magic angle. It is shown that exactly at the magic angle the spectrum corresponds to a frequency modulated powder pattern. This powder pattern leads to an understanding of the orientational behaviour of the director when a nematic is spun at the magic angle.

ISSN:0267-8292    

DOI:10.1080/02678298608086669

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Phase diagrams for the system nitrocellulose/tetrahydrofuran/ethanol have been mapped out at room temperature, for two different degrees of substitution of the polymer (2·32 and 2·72). The phases formed by particular compositions were identified by using polarized light microscopy. There is a range of compositions which separate into an isotropic phase and a liquid-crystalline phase; the concentrations involved are qualitatively in agreement with Flory's theory of phase separation in a solution of rigid rod-like molecules. Our plotted room temperature sections of the phase diagrams obey the Gibbs phase rule at all points. We report evidence for the formation of a crystallosolvate of nitrocellulose (degree of substitution 2·72) and ethanol. The crystallosolvate formation only appears to be kinetically possible if there is initially also sufficient tetrahydrofuran present to dissolve the polymer.

ISSN:0267-8292    

DOI:10.1080/02678298608086670

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Power Samples of Three Alkylthio Substituted Triphenylenes have been Investigated by X-ray diffraction. All have a hexagonal columnar Dhdphase. In one compound, a phase transition DhoDhdis found, in which the hexagonal lattice of columns remains unaffected by the order-disorder transition within the columns.

ISSN:0267-8292    

DOI:10.1080/02678298608086671

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The hypersound velocity in a series of binary mixtures containing the constituents 4-n-pentyl-4′-cyanobiphenyl and 4-cyano-4′(2-methyl)butoxybiphenyl has been measured using Brillouin scattering techniques. Measurements have been made in the isotropic phase of the mixtures over the temperature range 30°C to 80°C. A simple theory for the observed velocity variations is proposed and compared with the experimental data. Agreement is found to be excellent over the temperature range studied.

ISSN:0267-8292    

DOI:10.1080/02678298608086672

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0267-8292    

DOI:10.1080/02678298608086663

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor