The effect of nature of polyions and treatment after deposition on wetting characteristics of polyelectrolyte multilayers

The sequential adsorption of oppositely charged polyelectrolytes (PE) occurs to be a powerful tool for obtaining various materials of precisely defined properties. The interfacial features of PE multilayer films are governed by the choice of polycation/polyanion pairs and the conditions of film formation. Additionally, the long time exposure to the conditions different than that encountered during formation usually affects polyelectrolyte multilayer structure. The wettability of heterogeneous surfaces produced by ‘layer-by-layer’ (LbL) adsorption of polyelectrolytes was investigated in this work.We focused on the influence of film treatment after deposition on wetting properties of obtained multilayers. The effect of the nature of the first layer was also studied. Apart from simple arrangements: (polyallylamine hydrochloride)/ (polysodium 4-styrenesulfonate) (PAH/PSS) and (poly-L-lysine hydrobromide)/(poly-L-glutamic acid sodium salt) (PLL/PGA) more complicated structures were considered having as a first layer two types of polyethylene imines (PEI) of different molecular weight. Wetting properties of such polyelectrolyte films were determined experimentally by contact angle measurements using technique of direct image analysis of the shape of sessile drop.