The reaction between oppositely charged polyelectrolytes leading to the formation of a polyelectrolyte complex was used to modify the surface of organic and inorganic polymers. In this manner it was possible to prepare a strongly cationic surface charge on materials like cellulose, polyester, diatomaceous earth and clay. The surface was characterized by zeta potential measurements, dyestuff adsorption and electron microscopy. The degree of cationic functionality is strongly influenced by the stoichiometric ratio between polyanion and polycation and the pH value during reaction. The reaction was successfully used to modify filter sheets, free of asbestos, usually applied in the food and pharmaceutical industries. Filters with a high adsorption capacity for bacteria (Serratia marcescens ATCC 14756; > 10(11) colony forming units cm-2) and pyrogens (> 3g of pyrogen standard m-2) were obtained this way in an aqueous medium.
