摘要:

Seven novel diacetylenes have been synthesised, with six of these containing a pyridine ring directly conjugated to the main diacetylene unit. Values of χ2and χ3for these diacetylenes as guests in a guest-host polymer matrix (polysiloxane) have been obtained. High values of χ2are shown to depend on the presence of the pyridine ring whereas the highest values of χ3are obtained for the lesser conjugated diacetylenes.

ISSN:1058-725X    

DOI:10.1080/10587259508034543

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The dielectric loss spectrum of a side chain liquid crystal polymer (SCLCP) has been measured from 10 Hz to 100 kHz in the smectic phase. Three liquid crystalline siloxane polymers are examined, a homopolymer and two random copolymers, all of which contain a chiral smectic mesogen and an eleven-methylene spacer in the side chain. Two dielectric relaxations have been observed, the high-frequency α and low-frequency δ processes. The effect of the copolymer morphology in these SCLCPs is to increase the dielectric relaxation strength of the δ process relative to the α process and to cause increased overlap between the two peaks. These two observations suggest that the copolymer structure aids large scale reorientations in the δ process because of increased cooperativity with the backbone.

ISSN:1058-725X    

DOI:10.1080/10587259508034544

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The crystal and molecular structures of diethyl 6-[4-(4′-nitrophenylazo)phenoxy]hexylmalonate (1) as a comonomer in the synthesis of liquid-crystalline polymers and its 2′-nitrophenyl isomer (2) have been determined by X-ray analysis. Both compounds crystallize in space group P1with two molecules per unit cell and the following lattice parameters.1:a= 7.995(2),b= 10.699(2),c= 15.021(4) Å,a= 95.04(2),β= 96.54(2),γ= 94.72(3)°.2:a= 8.912(2),b= 9.664(2),c= 16.064(4) Å, α = 98.68(2),β= 97.54(1),γ= 105.11(1)°. The structures were solved by direct methods and refined toR(wR) values of 0.082 (0.068) and 0.071 (0.076), respectively.

ISSN:1058-725X    

DOI:10.1080/10587259508034545

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Helfand's lattice theory of polymer interface has been extended to deal with the interface between thermotropic small molecular liquid crystals and flexible polymers. The main findings of the theoretical calculations are: (1) the interface of flexible polymer and the ordered nematic liquid crystal is very narrow due to the fact that the ordered nematic phase excludes strongly the flexible polymer segments; (2) the interfacial tension and the anisotropic factors of polymer bonds posses a first order transition, when the liquid crystal-rich phase undergoes the isotropic to nematic phase transition, which is characterized mainly by the fact that polymer bonds prefer to return back to the saturated polymer solution phase by reducing the probability of stretching into the liquid crystalline phase.

ISSN:1058-725X    

DOI:10.1080/10587259508034546

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Synthesis and thermal properties of ω-[2-(4-X-phenoxycarbonyl)phenoxycarbonyl)-5-alkoxyphenoxy]alkyl and ω-[2-(4-X-phenoxycarbonyl)-5-alkoxyphenoxyalkyl poly-acrylates (X=n-alkoxyl or cyano group) have been reported. The homologs show a nematic phase,and a smectic phase as well as the nematic one is also formed when both terminal alkoxy chains of the core moiety are suitably long. On the cooling process, all the derivatives form a glassy phase corresponding to the prestates. The results will be discussed in terms of the molecular structure.

ISSN:1058-725X    

DOI:10.1080/10587259508034547

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The crystal and molecular structure of the nematogenic compound 2-n-nonyl-1,4-phenylene bis(4-n-octyloxybenzoate) (NPOB) has been determined at – 100°C and at room temperature by X-ray analysis. NPOB crystallizes in space group P1with two molecules in a unit cell of dimensions (values of the room temperature investigation are given in brackets)a= 9.878(2) [10.165(4)],b= 12.700(3) [12.863(5)],c= 17.830(4) [17.940(6)] Å, α = 71.83(2) [69.65(2)],β= 84.58(2) [85.23(2)],γ= 76.11(2) [75.43(2)]°. The structure was solved by direct methods and refined to an R value of 0.056 [0.108]. The most striking features of the molecular structure are theall-trans-conformation of the laterally branched nonyl group and the nearly parallel alignment of all three alkyl substituents. The crystal structure is characterized by a parallel arrangement and an interlocked packing of the molecules.

ISSN:1058-725X    

DOI:10.1080/10587259508034548

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The phase diagrams of following binary soap systems (soap = K-myristinate = KC14) were examined by polarization microscopy: system KC14/glycerol (G), KC14/ethylene glycol (E) and KC14/butylene glycol (E). Comparing these three phase diagrams, we found alterations in types of phase diagrams that depends on the chemical structure of the solvent. The following polymorphism were observed: In the system KC14/G: C↭G↭H↭I↭L↭S (C = crystalline phase, G = gel phase, H = hexagonal phase, I = isotropic phase, L = lamellar phase, S = isotropic solution). In the system KC14/E: C↭G↭L↭S and in the system KC14/B the same phase sequence: C↭G↭L↭S.

ISSN:1058-725X    

DOI:10.1080/10587259508034549

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Homologues series of some derivatives of 3,5-(4-substituted phenyl)-1,2,4-oxydiazole were synthesized and their phase behavior studied. Introduction of the pentagonal heteroaromatic ring leads to significant changes in mesomorphic behavior in comparison with analogous compounds containing the phenyl ring. The synthesised compounds exhibit smectic and nematic phases.

ISSN:1058-725X    

DOI:10.1080/10587259508034550

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The synthesis and liquid crystal properties of eighteen members of the homologous series of 4′-alkoxy-2,2′,3,3′,5,5′,6,6′-octafluorobiphenyl-4-yl-trans-4-alkylcyclohexane-1-carboxylates are reported. The compounds are low melting nematogens possessing a moderately wide N-I range and have refractive indices comparable with that of fused silica. Because of these properties the compounds may have a potential use as additives to mixtures for the TN mode or in applications where nematogens with a uniquely low refractive index are required.

ISSN:1058-725X    

DOI:10.1080/10587259508034551

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Brochard-de Gennes continuum model of ferronematics—magnetic suspensions with the nematic liquid-crystalline carrier—is modified to take into account the finiteness of energy of the nematic molecules anchoring on the particle surface. The developed approach is specified to be capable to describe the equilibrium properties of real thermotropic ferronematics.

ISSN:1058-725X    

DOI:10.1080/10587259508034552

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor