The effect of nature of polyions and treatment after deposition on wetting characteristics of polyelectrolyte multilayers Marta Kolasin ´ska * , Piotr Warszyn ´ski Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, 30-239 Cracow, Poland Available online 19 March 2005 Abstract 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 inves- tigated 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. # 2005 Elsevier B.V. All rights reserved. Keywords: ‘Layer-by-layer’ deposition; Polyelectrolytes; Multilayers; Contact angle; Wetting 1. Introduction The layer-by-layer (LbL) deposition technique used for sequential adsorption of oppositely charged poly- electrolytes (PE) is an efficient method for obtaining multilayer structures [1,2]. It has progressed signifi- cantly since introduction by Decher et al. [3] of the basic principle of multilayer materials formation using alternating adsorption of PE. This technique allows controlling structure and the total film thickness on a molecular level [4–6]. As the sequential adsorption of PE is electrostatically driven [7–10], the LbL method is very versatile (can be applied to any charged surface) and such self-assembled polyelectrolyte multilayers have a great application potential [11]. A possibility of combination of various polyelectrolytes opens a wide range of practical usage of such materials [7,12]. They can be applied for modification of surface properties, which has a special meaning in biomaterial area or as www.elsevier.com/locate/apsusc Applied Surface Science 252 (2005) 759–765 * Corresponding author. Tel.: +48 12 6395128. E-mail address: nckolasi@cyf-kr.edu.pl (M. Kolasin ´ska). 0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.02.060