ADSORPTION OF IONS ONTO POLYMER SURFACES AND ITS INFLUENCE ON ZETA-POTENTIAL AND ADHESION PHENOMENA

The adhesion behavior that governs many technologically and biological ly relevant polymer properties can be investigated by zeta potential m easurements with varied electrolyte concentration or pH. In a previous work [1] it was found that the difference of the adsorption free ener gies of Cl- and K+ ions correlates with the adhesion force caused by v an der Waals interactions, and that the decrease of adhesion strength by adsorption layers can be elucidated by zeta potential measurements. In order to confirm these interrelations, zeta potential measurements were combined with atomic force microscopy (AFM) measurements. Force- distance curves between poly(ether ether ketone) and fluorpolymers, re spectively, and the Si3N4 tip of the AFM device in different electroly te solutions were measured and analysed. The adsorption free energy of anions calculated from the Stern model correlates with their ability to prevent the adhesion between the polymer surface and the Si3N4 tip of the AFM device. These results demonstrate the influence of adsorpti on phenomena on the adhesion behavior of solids. The results obtained by AFM confirm the thesis that the electrical double layer of solid po lymers in electrolyte solutions is governed by ion adsorption probably due to van der Waals interactions and that therefore van der Waals fo rces can be detected by zeta potential measurements.