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Soft Matter and Biological Physics

Eur. Phys. J. E 2, 191-198

A small-angle X-ray scattering study of the isotropic and nematic phases of V2O5 suspensions

O. Pelletier 1 - C. Bourgaux 2 - O. Diat3 - P. Davidson 1 - J. Livage 4

1 Laboratoire de Physique des Solides, UMR 8502, Bât. 510, Université Paris Sud, 91405 Orsay Cedex, France
2 Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, UMR 130, Université Paris Sud, 91405 Orsay Cedex, France - DRFMC/SI3M/PCI, CEA Grenoble, 17 av. des Martyrs, 38054 Grenoble Cedex 9, France
3 Laboratoire de Chimie de la Matière Condensée, UMR 7574, Université Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris, France
davidson@lps.u-psud.fr

Received 21 July 1999 and Received in final form 17 December 1999

Abstract
We report small-angle X-ray scattering experiments performed in both the isotropic and nematic phases of aqueous V2O5 suspensions. We show that the scattering in the isotropic phase can be well described in the whole accessible q-range by only considering the form factor of non-interacting ribbons. We investigate the influence of concentration and pH on the dimensions of V2O5 ribbons and show that these parameters do not have any significant effect, as long as the system stays well within the chemical stability domain of the ribbons. We then show that nematic single domains display an anisotropic small-angle scattering pattern, even at scattering vectors small compared to that at which a characteristic correlation peak is observed. This feature is expected for a nematic phase, but was rarely observed. We finally try to describe this scattering within the framework of theories developed for the structure factor of a nematic polymer, and we reach the conclusion that chain ends are certainly important to understand this pattern.

PACS
61.10.Eq X-ray scattering (including small-angle scattering) - 61.30.-v Liquid crystals - 82.70.DdColloids

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