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Liquid crystalline elastomers: the relationship between macroscopic behaviour and the level of backbone anisotropy

Hirschmann, H., Roberts, P.M.S., Davis, F.J., Guo, W., Hasson, C.D. and Mitchell, G.R. (2001) Liquid crystalline elastomers: the relationship between macroscopic behaviour and the level of backbone anisotropy. Polymer, 42 (16). pp. 7063-7071. ISSN 0032-3861

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To link to this item DOI: 10.1016/S0032-3861(01)00135-5

Abstract/Summary

Nematic monodomain liquid crystalline elastomers have been prepared through in situ cross-linking of an acrylate based side-chain liquid crystalline polymer in a magnetic field. At the nematic–isotropic transition, the sample is found to undergo an anisotropic shape change. There is found to be an increase in dimensions perpendicular — and a decrease parallel — to the director, this is consistent with alignment of the polymer backbone parallel to the direction of mesogen alignment in the nematic state. From a quantitative investigation of this behaviour, we estimate the level of backbone anisotropy for the elastomer. As second measure of the backbone anisotropy, the monodomain sample was physically extended. We have investigated, in particular, the situation where a monodomain sample is deformed with the angle between the director and the extension direction approaching 90°. The behaviour on extension of these acrylate samples is related to alternative theoretical interpretations and the backbone anisotropy determined. Comparison of the chain anisotropy derived from these two approaches and the value obtained from previous small-angle neutron scattering measurements on deuterium labelled mixtures of the same polymer shows that some level of chain anisotropy is retained in the isotropic or more strictly weakly paranematic state of the elastomer. The origin and implications of this behaviour are discussed.

Item Type:Article
Refereed:Yes
Divisions:Interdisciplinary centres and themes > Chemical Analysis Facility (CAF) > Electron Microscopy Laboratory (CAF)
ID Code:26800
Publisher:Elsevier

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