Concentration Dependence of Polymer Adsorption on Clay Surfaces by Small Angle Neutron Scattering

Understanding the basis of polymer adsorption behavior on inorganic surfaces is critical in a variety of industrial applications, including water treatment, pigmented architectural coating formulations, cement formulations, and pulp and paper manufacture. To further the understanding of the adsorption process, the adsorption behavior of select high molecular weight polymers onto a model clay surface in aqueous formulations is studied as a function of polymer concentration by small angle neutron scattering (SANS). The model clay used in the study is Laponite, which has a well-defined disk-like morphology and narrow distribution of platelet sizes. The SANS results were fit using a core-shell cylinder model allowing extraction of the adsorbed polymer layer dimensions on both the radial and face of the clay particles. The polymer layer thickness and density were found to depend on the polymer concentration, progressively adsorbing onto the radial and then facial locations of the clay particles. The results are compared with other studies of polymer adsorption onto surfaces and put in context with existing theories for polymer adsorption.