DEPENDENCE OF THE FAR-FIELD EFFECTIVE POTENTIAL ON SURFACE INHOMOGENEITIES

Many surfaces encountered in colloid science are formed by the adsorpt ion of surfactants or polymers on solid surfaces. Due to the formation of surface aggregates, the charge distributions of such surfaces may be nonuniform. Furthermore, these surfaces are expected to have region s with different electrostatic properties due to the presence of two o r more different materials. In this paper, we propose a model consisti ng of periodically alternating regions of constant potential and const ant charge, in order to account for the possibility of different regio ns on the surface possessing different electrostatic properties. Speci fically, we consider the behavior of the far field effective electrost atic potential of this model surface when it is immersed in an electro lyte, i.e., the potential associated with the asymptotic exponential t ail of the potential distribution in the electrolyte, In doing so, we find the previously unreported phenomenon that the effective potential is strongly dependent on the surface morphology and its associated le ngth scale. Furthermore, we find that there also exists the possibilit y that the constant charge regions will be ''invisible'' to the potent ial distribution. These results have direct implications for general n onuniform charge regulating surfaces. (C) 1996 Academic Press, Inc.