| Issue |
J. Chim. Phys.
Volume 87, 1990
|
|
|---|---|---|
| Page(s) | 1901 - 1922 | |
| DOI | https://doi.org/10.1051/jcp/1990871901 | |
| Published online | 29 May 2017 | |
Etude de la transition sol-gel en milieu micellaire inverse. II : Principes fondamentaux
1
Laboratoire de Physicochimie des Matériaux, CNRS URA 1312, ENSCM-8, rue de l'Ecole Normale, 34053 Montpellier Cedex 1, France.
2
Laboratoire de Physicochimie des Systèmes Polyphasés, CNRS URA 330, USTL-Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France.
Dans ce travail nous présentons les principes fondamentaux de la formation de gels d'oxydes minéraux en milieu micellaire inverse. L'utilisation d'une microémulsion comme milieu réactionnel a permis la préparation de gels d'alcoxydes de métaux de transition en contrôlant parfaitement les étapes d'hydrolyse et de condensation. Un mécanisme de transition sol-gel est proposé faisant intervenir un phénomène de percolation entre les particules formées dans le sol. La structure locale de ces particules peut être considérée comme composée de cylindres interconnectés formant un réseau de dimension fractale.
Abstract
In this paper fundamentals of sol-to-gel transition in reversed micelles microémulsion are presented. Metal-organic derived gels have been prepared using transition metal alkoxides solutions in decane, containing water trapped in non ionic surfactant reversed micelles. Conditions for the preparation of reversed micelles microemulsions capable of promoting hydrolysis and condensation of transition metal alkoxides are described. Iso-propyl and tertio-butyl titanates have been chosen as starting alkoxides for this study. Hydrolysis and condensation reactions have been performed by controlling release of water molecules from reversed micelles allowing gel formation without precipitation phenomena or side reactions. The kinetics can be governed by only three parameters n, h and m, respectively the water/surfactant, water/alkoxide and alkoxide/solvent ratios. The porous structure of the gels has been characterized and a percolation mechanism is proposed to describe gel formation from single particles growing into the sol. A fractal structure has been evidenced for particles constituting the gel framework.
© Elsevier, Paris, 1990