Volume 73, Number 4, February 2006
|Page(s)||553 - 559|
|Section||Condensed matter: structural, mechanical and thermal properties|
|Published online||18 January 2006|
Orientational order and dynamics of a nematic liquid crystal in porous media
Hahn-Meitner Institut - 100 Glienicker Strasse, 14109 Berlin, Germany
2 Laboratoire des colloïdes, verres et nanomatériaux, UMR 5587 CNRS-Université Montpellier II - Place E. Bataillon, 34095 Montpellier, France
3 Laboratorio de Física Estadística de Sistemas Desordenados, Centro de Física, IVIC Apartado 21827, Caracas 1020A, Venezuela
Accepted: 2 January 2006
We report on orientational order and dynamics of a nematic liquid crystal confined in porous silica. 13C NMR lineshape is used as a fingerprint for this study. A procedure based on exchange of non-coupled sites is implemented in order to obtain the corresponding local order parameter S and the characteristic time for molecular reorientation τ. Our results evidence that in the nematic phase, S decreases when confinement increases. By means of Langevin dynamics simulations of confined liquid crystals, we show that this behavior is due to topological defects, originated by the absorbed-layers phenomenon as a consequence of the strong anchoring of these molecules on silica surfaces.
PACS: 61.30.Hn – Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions / 61.30.Jf – Defects in liquid crystals / 64.70.Md – Transitions in liquid crystals
© EDP Sciences, 2006
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