Exclusion-Zone Formation From Discontinuous Nafion Surfaces

Many hydrophilic materials in aqueous solution show near-surface zones that exclude suspended colloids and dissolved molecules. These exclusion zones (EZs) can extend for tens to hundreds of micrometers from the hydrophilic surface, and show physicochemical properties that differ from bulk water. So far, only continuous surfaces of polymers, gels, or biological specimens have been studied. In this report, we explore the interactions between exclusion zones generated by discontinuous, regularly spaced EZ-generating surfaces, namely strips of Nafion on a glass surface. Various inter-strip spacings were studied. When Nafion surfaces are separated by 100 micrometers or less, EZs merged with one another, forming a single, continuous, stable EZ. Separations larger than 100 micrometers produced discontinuous EZs that did not merge. This result has implication for the mechanism by which independent EZs can merge with one another.