Electrodeposition of a weak polyelectrolyte hydrogel: remarkable effects of salt on kinetics, structure and properties

The electrodeposition of weak polyelectrolyte hydrogels involves an array of subtle interactions. We report that salt dramatically affects the kinetics of chitosan electrodeposition, and the structure and properties of deposited hydrogel films. The kinetics of film growth was measured using a microfluidic device which demonstrated that salt increases both the rate and extent of deposition. The structure of the deposited film was measured by atomic force microscopy which showed that salt addition to the deposition solution leads to films with greater surface roughness (consistent with the tendency of chitosan to aggregate at high salt concentrations). The properties of the deposited films were measured by quartz crystal microbalance with dissipation (QCM-D) which showed that salt addition to the deposition solution leads to films with substantially reduced moduli (over 3-orders-of-magnitude). These results illustrate the potential to tailor electrodeposition to meet specific requirements for the diverse applications in the life and medical sciences.