Effect of Solids Concentration on Polymer Adsorption and Conformation

Abstract

1. ABSTRACT The effect of solids concentration on the adsorption and conformation of polymers at solid/liquid interface was investigated using depletion adsorption and fluorescence techniques. The fluorescence of pyrene labeled polyethylene oxide at silica/water interface as a function of solids concentration revealed a surprisingly measurable change in polymer conformation as the solids content was increased. Adsorption density as well as coiling of the polymers was found to decrease with increase in solids concentration. These changes are correlated with the rheological behavior of the suspensions. 2. INTRODUCTION Concentrated particulate suspensions are widely used for coatings, paints, electronic pastes, clay and ceramic slurries in many industrial processes. To maintain the stability of these concentrated suspensions and to facilitate the processing, polymers are frequently used for controlling the suspension rheology. 1 Although polymers are currently used for dispersing concentrated suspensions, the role of polymer properties, particularly their conformation and orientation, in stabilization of colloidal particles in concentrated slurries remains unclear. Recently, we have used fluorescence spectroscopy to estimate the conformation and interaction of polymers at surfaces. 2-4 Information obtained for polymer conformation at solid/liquid interface has been correlated with the flocculation properties of particulate suspensions. In this paper, effects of solids concentration on polymer adsorption and con-formation on selected model systems are presented.