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Biaxial optical properties of thermotropic random copolyesters

Viney, C., Mitchell, G.R. and Windle, A.H. (1985) Biaxial optical properties of thermotropic random copolyesters. Molecular Crystals and Liquid Crystals, 129 (1-3). pp. 75-108. ISSN 1563-5287

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To link to this item DOI: 10.1080/15421408408084167


The optical microstructures of thin sections of two liquid crystalline polymers are examined in the polarizing microscope. The polymers are random copolyesters based on hydroxybenzoic and hydroxynaphthoic acids (B-N), and hydroxybenzoic acid and ethylene terephthalate (B-ET). Sections cut from oriented samples, so as to include the extrusion direction, show microstructures in which there is no apparent preferred orientation of the axes describing the local optical anisotropy. The absence of preferred orientation in the microstructure, despite marked axial alignment of molecular chain segments as demonstrated by X-Ray diffraction, is interpreted in terms of the polymer having biaxial optical properties. The implication of optical biaxiality is that, although the mesophases are nematic, the orientation of the molecules is correlated about three (orthogonal) axes over distances greater than a micron. The structure is classified as a multiaxial nematic.

Item Type:Article
Divisions:Interdisciplinary centres and themes > Chemical Analysis Facility (CAF) > Electron Microscopy Laboratory (CAF)
ID Code:26922
Publisher:Taylor and Francis

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