Surface interactions during polyelectrolyte multilayer buildup. 1. Interactions and layer structure in dilute electrolyte solutions

Abstract

We report the investigation of surface forces between polyelectrolyte multilayers of poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate sodium salt) (PSS) assembled on mica surfaces during film buildup using a surface force apparatus. Up to four polyelectrolyte layers were prepared on each surface ex situ, and the surface interactions were measured in 10-4 M KBr solutions. The film thickness under high compressive loads (above 2000 μN/m) increased linearly with the number of deposited layers. In all cases, the interaction between identical surfaces at large separations (>100 Å from contact) was dominated by electrostatic double-layer repulsion. By fitting DLVO theory to the exper..