Dan Ben-Yaakov, David Andelman, Haim Diamant
When solid surfaces are immersed in aqueous solutions, some of their charges can dissociate and leave behind charged patches on the surface. Although the charges are distributed heterogeneously on the surface, most of the theoretical models treat them as homogeneous. For overall non-neutral surfaces, the assumption of surface charge homogeneity is rather reasonable, since the leading terms of two such interacting surfaces depend on the non-zero average charge. However, for overall neutral surfaces, the nature of the surface charge distribution is crucial in determining the inter-surface interaction. In the present work we study the interaction between two charged surfaces across an aqueous solution for several charge distributions. The analysis is preformed mainly within the framework of the linearized Poisson-Boltzmann theory. For periodic charge distributions the interaction is found to be repulsive at small separations, unless the distributions are completely out of phase with respect to each other. For quenched random charge distributions we find that due to the presence of the ionic solution in between the surfaces, the inter-surface repulsion dominates over the attraction in the linear regime of the Poisson-Boltzmann theory. We also discuss the non-linear regime of the interaction in the limit of large charged domains on the surfaces. Surprisingly, in this limit the overall interaction may become attractive in contrast to the linear regime.
View original:
http://arxiv.org/abs/1205.2855
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