Sommaire:

Nanoclays e.g. natural Na-montmorillonite and synthetic Laponite are colloids of layered minerals. When dispersed in water, these powdered minerals swell on absorption of water and exfoliate into smaller entities, known as tactoids, with charge double layers on their surfaces. The aqueous suspensions can exhibit a spontaneous ergodicity breaking phase transition from free flowing liquids to nonequilibrium, kinetically arrested states such as gels and glasses at low particle concentrations [1]. These classes of materials are being used extensively in polymer nanocomposite, as rheological modifiers, gas absorbents and recently in drug delivery researches. The understanding of the physicochemical properties of clay dispersions under different conditions can therefore help to predict and control their final macroscopic behavior. In this talk, I shall demonstrate the use of ultrasound attenuation spectroscopy to estimate the degree of exfoliation (the dispersibility) of tactoids in samples of different ages and of different concentrations of clay and added electrolytes. Our analysis shows that a substantial fraction of the aggregates in glassy suspensions are actually tactoids that are composed of more than one platelet [2]. We further evaluate the influence of clay dispersibility on the suspension stability and the mechanical properties of arrested phases at different ionic conditions by using electroacoustics and rheometry.

Pour plus d'informations, merci de contacter Gross M.