Eur. Phys. J. E 7, 5-11 (2002)
Novel twist grain boundary smectic-C phasesM. Brunet1, L. Navailles1 and N.A. Clark2
1 GDPC - UMR 5581, Université Montpellier II, F34095 Montpellier Cedex 05, France
2 Department of Physics, Ferroelectric Liquid Crystal Materials Research Center, University of Colorado, Boulder Boulder, CO, USA 80309
(Received 15 March 2001)
Several new kinds of smectic-C twist grain boundary phases (TGBC) have been observed during the last few years. These pure compounds or mixtures exhibit unusual textures with polygonal lattices (square or hexagonal grids) in the plane normal to the TGB helix. The structure of these new phases seems to be complex and different from reported and predicted TGBC phases. In this article, we review the main results obtained on these different new phases, and we propose new TGBC structures based on the well-known splayed polarization -twisted director structures adopted by chiral smectic-C's in planar aligned (bookshelf) cells. The observed square or hexagonal lattices are made of superimposed pairs of unwinding lines due to the suppression of the helix within smectic-C blocks by the grain boundaries (unwinding walls). A lattice-free TGBC occurs if the helix within smectic-C blocks is suppressed completely.
61.30.-v - Liquid crystals.
61.30.Jf - Defects in liquid crystals.
61.30.Eb - Experimental determinations of smectic, nematic, cholesteric, and other structures.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002