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Spectroscopic Studies of Liquid Crystals Confined in Sol-gel Matrices

Published online by Cambridge University Press:  21 March 2011

Carlos Fehr ,
Philippe Dieudonne ,
Christophe Goze Bac ,
Philippe Gaveau ,
Jean-Louis Sauvajol  and
Eric Anglaret
Carlos Fehr
Affiliation:
Groupe de dynamique des Phases Condensées, UMR CNRS 5581, Université Montpellier II, Montpellier, France
Philippe Dieudonne
Affiliation:
Groupe de dynamique des Phases Condensées, UMR CNRS 5581, Université Montpellier II, Montpellier, France
Christophe Goze Bac
Affiliation:
Groupe de dynamique des Phases Condensées, UMR CNRS 5581, Université Montpellier II, Montpellier, France
Philippe Gaveau
Affiliation:
Groupe de dynamique des Phases Condensées, UMR CNRS 5581, Université Montpellier II, Montpellier, France
Jean-Louis Sauvajol
Affiliation:
Groupe de dynamique des Phases Condensées, UMR CNRS 5581, Université Montpellier II, Montpellier, France
Eric Anglaret
Affiliation:
Groupe de dynamique des Phases Condensées, UMR CNRS 5581, Université Montpellier II, Montpellier, France
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Abstract

Thermotropic liquid crystals (5CB and 8CB) were confined in silica porous matrices (xerogels and xero-aerogels) with different pore sizes. The structure and dynamics of confined liquid crystals were studied by Raman spectroscopy and Nuclear Magnetic Resonance. In Raman, the frequency of the CN stretching peak is a good probe of the smectic_A-crystal phase transition. The CN peak is observed to split upon quenching. This suggests a coexistence of crystalline and supercooled liquid phases for confined LC which was not observed in the bulk. In NMR, strong differences in both chemical shifts and linewidths are observed in confinement with respect to the bulk. We present a model which analyses the changes in the spectra in terms of changes of the order parameter and molecular dynamics for the confined LC.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 651: Symposium T – Dynamics in Small Confining Systems V , 2000 , T7.2.1.
Copyright
Copyright © Materials Research Society 2001

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