pH-Induced Release of Polyanions from Multilayer Films

Abstract

We discovered pH-induced selective desorption and re-adsorption of weak polyacid chains from polyacid/polybase layer-by-layer films. In situ ATR-FTIR confirms the selectivity of polyacid release and shows that film response is caused by pH-induced charge imbalance. Experimentally, the characteristic time of chain release, τ, scales with molar mass, Mw, as Mw1.1�0.1. A new theoretical model of "sticky gel electrophoresis" of entangled polyacids agrees with experiments and predicts τ ~ Mw H, where H is film thickness. Neutron reflectivity shows that polyacid release results in disordering of the film structure.