Issue |
Europhys. Lett.
Volume 48, Number 1, October I 1999
|
|
---|---|---|
Page(s) | 53 - 59 | |
Section | Condensed matter: structure, mechanical and thermal properties | |
DOI | https://doi.org/10.1209/epl/i1999-00113-x | |
Published online | 01 September 2002 |
The effect of attractive interactions on the nematic order of
gels
1
Laboratoire de Physique des Solides, Bât. 510, URA 002 CNRS, Université Paris Sud 91405 Orsay cedex, France
2
Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, Bât. 209D UMR 130 CNRS, Université Paris Sud - 91405 Orsay cedex, France
3
Laboratoire de Chimie de la Matière Condensée, URA 1466 CNRS Université Pierre et Marie Curie - 4 Place Jussieu, 75252 Paris cedex, France
Received:
3
May
1999
Accepted:
26
July
1999
Aqueous suspensions of ribbons form a lyotropic nematic phase at volume fractions larger than
0.7%. We investigate the effect of adding a monovalent salt (NaCl) to this charge-stabilized system.
Without any added salt, the nematic ordering can be described by the Onsager model based on a hard-core
repulsive potential. Adding salt induces the gelation of these suspensions. Very unexpectedly, it also
induces the stabilization of the nematic phase with respect to the isotropic one in a way opposite
to the predictions of the Onsager model and to the usual behavior of typical hard-rod fluids. Larger salt
concentrations eventually lead to flocculation. These observations indicate the increasing influence of
attractive interactions which we argue are most probably van der Waals attractions.
PACS: 61.30.-v – Liquid crystals / 82.70.Dd – Colloids / 82.70.Gg – Gels and sols
© EDP Sciences, 1999
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