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    New 2-in-1 Polyelectrolyte Step-by-Step Film Buildup without Solution Alternation: From PEDOT-PSS to Polyelectrolyte Complexes

    Year: 2012

    Journal: Langmuir, 2012, 28 (23), pp 8681–8691, 20120922

    Authors: Christine de Saint-Aubin †, Joseph Hemmerlé ‡, Fouzia Boulmedais §// , Marie-France Vallat †, Michel Nardin †, and Pierre Schaaf *§//

    Last authors: Pierre Schaaf

    Organizations: † Centre National de la Recherche Scientifique, Institut de Science des Matériaux de Mulhouse, LRC 7228 − UHA, 15 rue Jean Starcky, BP 2488, 68057 Mulhouse cedex, France ‡ Institut National de la Santé et de la Recherche Médicale, UMR 977, 11, rue Humann, 67085 Strasbourg cedex, France § Centre National de la Recherche Scientifique, Institut Charles Sadron, UPR 22, 23 rue du Loess, BP 84047, 67034 Strasbourg cedex 2, France //International Center for Frontier Research in Chemistry (icFRC), 8 allée Gaspard Monge, 67083 Strasbourg, France

    Country: France

    Although never emphasized and increasingly used in organic electronics, PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)) layer-by-layer (lbl) film construction violates the alternation of polyanion and polycation rule stated as a prerequisit for a step-by-step film buildup. To demonstrate that this alternation is not always necessary, we studied the step-by-step construction of films using a single solution containing polycation/polyanion complexes. We investigated four different systems: PEDOT-PSS, bPEI-PSS (branched poly(ethylene imine)-poly(sodium 4-styrene sulfonate)), PDADMA-PSS (poly(diallyl dimethyl ammonium)-PSS), and PAH-PSS (poly(allylamine hydrochloride)-PSS). The film buildup obtained by spin-coating or dipping-and-drying process was monitored by ellipsometry, UV–vis-NIR spectrophotometry, and quartz-crystal microbalance. The surface morphology of the films was characterized by atomic force microscopy in tapping mode. After an initial transient regime, the different films have a linear buildup with the number of deposition steps. It appears that, when the particles composed of polyanion-polycation complex and complex aggregates in solution are more or less liquid (case of PEDOT-PSS and bPEI-PSS), our method leads to smooth films (roughness on the order of 1–2 nm). On the other hand, when these complexes are more or less solid particles (case of PDADMA-PSS and PAH-PSS), the resulting films are much rougher (typically 10 nm). Polycation/polyanion molar ratios in monomer unit of the liquid, rinsing, and drying steps are key parameters governing the film buildup process with an optimal polycation/polyanion molar ratio leading to the fastest film growth. This new and general lbl method, designated as 2-in-1 method, allows obtaining regular and controlled film buildup with a single liquid containing polyelectrolyte complexes and opens a new route for surface functionalization with polyelectrolytes.