Interaction of polymer with discotic clay particles

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 labeling can the structure o f the adsorbed polymer layers be determined. The contrast variation techniq ue is specifically used to determine separately the different partial struc ture factors of the clay and polymer. In this way the signal of the adsorbe d chains is separated from the signal of the free chains in the dilute regi me. Attempts have also been made to characterize the structure in the conce ntrated regime of laponite with polymer.