SURFACE MODIFICATION BY POLYELECTROLYTE COMPLEXES

Co-operative interaction between water-soluble polymers has been a top ic of investigation world-wide because of their importance from both s cientific and practical viewpoint. Our work is focused on the investig ation of complex formation between oppositely charged polyelectrolytes and the interaction with inorganic fine particles for example negativ ely charged quartz powder and silicic acid. The cationic polyelectroly tes tested were poly(diallyldimethylammoniumchloride) (PDADMAC) and po lyallyl-amine (PAA), differing in the molar mass, the molecular geomet ry and charge density. The anionic polyelectrolytes used were copolyme rs of maleic acid with propylene (MS-P), stryrene (MS-Sty) and methyls tyrene (MS-alpha-MeSty). Two different principles of surface modificat ion with polyelectrolyte complexes were tested. On the first hand prev ious prepared non-stoichiometric complex dispersions carrying cationic excess charges were contacted to the substrate and on the other hand the polycation was preadsorbed on the oppositely charged surface befor e an equimolar amount of polyanion was added. Both methods show differ ent results in the reachable surface charge. It is important to note t hat a synergistic effect with respect to the cationic surface charge w as found in dependence on the surface charge density of the substrate, the chosen polyelectrolyte combinations and the used modification pro cedure. From the results it is concluded that steric factors of the po lyelectrolytes are responsible for conformation and stoichiometry of t he formed polyelectrolyte complexes and thus the effectiveness of char ge modification with polyelectrolyte complex is also determined by the characteristics of the used polyions.