Bulk streaming potential in poly(acrylic acid)/poly(acrylamide) hydrogels

The streaming potential through poly(acrylic acid)-co-acrylamide polymer hydrogel (poly-AA-co-AM) membranes has been measured as a function of gel composition and ionic strength of the solvent. Polyelectrolyte hydrogels have important potential applications as mechanical transducers. The current work aims at providing a quantitative basis to understanding the relationship between gel composition and structure and the electromechanical coupling properties. The streaming potential increases in magnitude with the spatial density of negative charges in the gel, up to a saturation point where the density of charges on the polymer backbone becomes comparable to the salt concentration of the equilibrating solution. A simple theory of coupled charge and solvent transport based on the model proposed by de Gennes et al. [Europhys. Lett. 2000, 50, 513] quantitatively accounts for the observed effects