Interaction of polymer with clays

Normally synthetic well defined monodisperse discotic laponite clays are kn own to form a gel phase at mass concentrations as low as a few percent in d istilled water. Hydrosoluble polymer polyethylene oxide was added to this i ntriguing clay system, it was observed that it either prevents gelation or slows it down extremely depending on the polymer weight, concentration or t he laponite concentration. Small Angle Neutron scattering (SANS) was used t o study these systems because only by isotopic labelling can the structure of the adsorbed polymer layers be determined. The contrast variation techni que is specifically used to determine separately the different partial stru cture factors of the clay and polymer. In this way the signal of the adsorb ed chains is separated from the signal of the free chains.