摘要:

The crystal structure and the molecular arrangement of 4′-pentyl-4-cyanobiphenyl (5CB) at 253 K are described. At 253 K the compound crystallized from pure ethanol as plates, as well as fine needles, both colourless. The crystal data for both crystal habits are within experimental error identical. The data for the plates were measured as:a= 8.249(5) Å,b= 16.022(4) Å,c= 10.935(3) Å β = 95.09(3)°, space group P21/a. Considering 2014 independent reflections, the structure was refined to a finalRvalue of 0.0588. In the case of the needles, with 1892 independent reflections,Rconverged to 0.0503. The torsion angle between the normals of the benzene rings in the biphenyl moiety was −26.3(3)°. Within the aliphatic chain an all-transconformation was given, but the orientation of the pentyl group relative to the plane of the attached aromatic ring was nearly vertical (− 90.5(3)°). The structure obtained is discussed in comparison with the lower homologues 1CB up to 4CB.

ISSN:0267-8292    

DOI:10.1080/02678299508031086

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This communication was stimulated by a meeting of the Sonderforschungsbereich 335, ‘Anisotrope Fluide’ at the Technische Universität Berlin, in December 1994. At this conference we realized that there are some very strong similarities between the melting processes of blue phases, twist grain boundary phases, and cubic D phases to the isotropic, amorphous liquid. In all three cases the melting appears to be a two stage process with a sharp melting enthalpy followed by a broad diffuse endotherm as the disorganized liquid is formed. In this article we wish to draw attention to similarities in the nature of these melting processes, to suggest a general descriptive model for the breakdown in molecular ordering, and to stimulate a theoretical debate in order to gain an understanding of the role of frustration phenomena in melting processes.

ISSN:0267-8292    

DOI:10.1080/02678299508031087

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

New cyclophosphazene derivatives incorporating five different mesogenic moieties have been synthesized and their liquid crystalline behaviour has been studied by DSC and polarizing optical microscopy. Smectic A and unclassified smectic 1 phases have been found for the first time in these cyclotriphosphazene derivatives. The relatively good thermal stability of the smectic phases of the mesomorphic cyclotriphosphazenes was interpreted in terms of the peculiar molecular shape of the cyclotriphosphazenes.

ISSN:0267-8292    

DOI:10.1080/02678299508031088

出版商:Taylor & Francis Group    

年代:1995

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:10.1080/02678299508031066

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor