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.