Effects of Applied Voltage and Solution pH in Fabricating Multilayers of Weakly Charged Polyelectrolytes and Nanoparticles

The relationship between solution pH and effects of applied voltage in layer-by-layer (LbL) self-assembly was investigated, using weakly charged polyelectrolytes and nanoparticles. Poly­(allylamine hydrochloride) (PAH)/poly­(acrylic acid) (PAA) films and PAH/SiO₂ nanoparticle films were fabricated at several solution pH conditions, by LbL self-assembly under an applied voltage. Adsorption behavior and surface morphology of films fabricated under applied voltages depended on the solution pH. A textured structure was formed by applied voltage at a specific pH for PAH/PAA films. The effect of applied voltage on film deposition was related to the electrical charge density and polymer chain conformation. The effects of applied voltage were higher, when the polymer electrical charge density was higher, that is, when the polymer chain exhibited a stretched structure. It was found that the amount of adsorption increased at all pH conditions under the applied voltage.