Eur. Phys. J. E 5, 353-357

Identification of a TGBA liquid crystal phase via its defects

Yu.A. Nastishin^{1, 2}, M. Kléman², J. Malthête³ and H.T. Nguyen<sup>4

1</sup>  Institute for Physical Optics, 23 Dragomanov str., Lviv 290005 Ukraine
²  Laboratoire de Minéralogie-Cristallographie de Paris (UMR7590), T16 case 115, 4 place Jussieu, F-75252 Paris cédex 05, France
³  Institut Curie, Section de recherche, CNRS UMR 168, 11 rue Pierre et Marie Curie, Paris cédex, 05 France
⁴  Centre de recherche Paul Pascal, CNRS UPR 8641, avenue Albert Schweitzer, 33600 Pessac cédex, France

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(Received 12 February 2001)

Abstract
We have shown that cholesteryl nonanoate, a thermotropic compound which is well known to exhibit pretransitional effects at the smectic A (SmA) cholesteric (N*) transition (W.L. McMillan, Phys. Rev. A 4, 1238 (1971); 6, 936 (1972)), has in fact a TGBA phase in between. Our arguments rely on the observation of new TGBA defects, either in Robinson spherulites cooled from the N* phase or in free-standing films. The same new defects can be obtained in a well-documented TGBA phase of a tolane compound. We analyze qualitatively the TGBA defects in both geometries, in particular their relation to the disclination radius of the N* Robinson spherulites.

PACS
61.30.Jf - Defects in liquid crystals.
61.72.-y - Defects and impurities in crystals; microstructure.
64.70.Md - Transitions in liquid crystals.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001