Polyelectrolyte layer-by-layer self-assembly at vibration condition and the pervaporation performance of assembly multilayer films in dehydration of isopropanol

Polyelectrolytes layer-by-layer (LbL) self-assembly multilayer films are mostly built up statically till now. In this work, positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged poly(sodium-p-styrenesulfonate) (PSS) LbL multilayer films were built up at vibration condition. The absorption and the thickness growth of multilayers were monitered by UV–vis spectrum and quartz crystal microbalance (QCM). The root mean square (RMS) surface roughness and morphology evolution of films were characterized by atomic force microscopy (AFM). LbL multilayer films, deposited on modified polyamide (MPA) reverse osmosis membrane, were subjected to pervaporation dehydration of water–isopropanol mixture. Vibration affects the UV–vis absorption amount and the thickness of the multilayer film, but it does not alter the film growth rule in presence or absence of added salt. Multilayer films built up at the vibration condition show higher selectivity with high permeation flux. This is attributed to the fact that the chains deposited orderly and the films formed are dense and smooth at the vibration condition.