Mechanism of exfoliation of clays

The exfoliated structures of lamellar clays offer potentials as precursor for formation of nano-structured materials. We explored the Synchrotron Radiation soft X-ray techniques and nuclear magnetic resonance to study the exfoliation of phyllosilicate clays by polymers. Experiments were carried out in dispersions containing approximately 1% weight phyllosilicate in 5% aqueous solution of poly(acrylic acid) at different temperatures. The clays were exfoliated as the reaction was performed at 85��C. X-ray photoemission spectroscopy indicated that the exfoliated structures were consisted of virtually pure silica nano-plates. 29Si nuclear magnetic resonance and oxygen K-edge near edge X-ray absorption fine structure indicated that the surface of the plates was terminated by high concentrations of the silanol groups, which created structural branches. The formation of the branches created a steric effect that inhibited the stacking of the plates, which eventually resulted in the exfoliation.