The rheological parameters of clay suspensions can be used to examine particle-particle interactions. The polymers that have been added to the clay suspensions interact with clay particles, according to their ionic or non-ionic character. In this Study, we have synthesized an organoclay (ONaMt) form of a Na-activated rnontrnorillonite (NaMt) and investigated theological and electrokinetic properties of their water based dispersions. After that, the medium is changed with water based solution of PU and the changes on the rheological and electrokinetic properties and the structural analysis of the materials were studied. All the results have been commented by taking the interaction between the clay and the polymer molecules into consideration. X-ray diffraction (XRD) studies showed that basal spacing of NaMt samples are more expandable, up to 22 angstrom, than ONaMt samples, which their expendabilities are relatively constant at about 19 angstrom. (C) 2009 Elsevier B.V. All rights reserved.