Supercritical Carbon Dioxide : a New Method for the Organomodification of Natural Clays

INTRODUCTION Clays, and more specifically 2 :1 phyllosilicates consisting of aluminoor magnesiosilicate negatively charged staked layers separated by van der Walls spacings where inorganic countercations (sodium, calcium,... cations) are located, can be associated with polymers to give interesting new materials called polymer/clay nanocomposites. Polymer/clay nanocomposites have been intensively studied this two past decades because very small amounts of clay have shown to greatly improve a bunch of polymer properties, if nano-dispersion in the polymer matrix (exfoliation) is achieved. This exfoliation, however, appears difficult to obtain due to the incompatibility between the naturally hydrophilic clay, and the most usually hydrophobic polymer matrix. Therefore, an ionic exchange between the interlayer cations of the clay and a cationic surfactant is necessary to render the interlayer spacings of the clay sufficiently organophilic to enhance the polymer/clay affinity.