14030 DOI: 10.1021/la901479z Langmuir 2009, 25(24), 14030–14036 Published on Web 08/13/2009 pubs.acs.org/Langmuir © 2009 American Chemical Society Tunable Synthesis of Prussian Blue in Exponentially Growing Polyelectrolyte Multilayer Films † Nicolas Laugel, ‡ Fouzia Boulmedais, ‡ Alae E. El Haitami, z,§ Pierre Rabu, ) Guillaume Rogez, ) Jean-Claude Voegel, z,§ Pierre Schaaf,* ,‡ and Vincent Ball* ,z,§ ‡ Centre National de la Recherche Scientifique, Unit e Propre de Recherche 22, Institut Charles Sadron, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France, z Institut National de la Sant e et de la Recherche M edicale, Unit e 977, 11 rue Humann, 67085 Strasbourg Cedex, France, § Universit e de Strasbourg, Facult e de Chirurgie Dentaire, 1 Place de l’H^ opital, 67000 Strasbourg, France, and ) Centre National de la Recherche Scientifique - Universit e de Strasbourg, Unit e Mixte de Recherche 7504, Institut de Physique et Chimie des Mat eriaux de Strasbourg, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France Received April 26, 2009. Revised Manuscript Received July 12, 2009 Polyelectrolyte multilayer (PEM) films have become very popular for surface functionalization and the design of functional architectures such as hollow polyelectrolyte capsules. It is known that properties such as permeability to small ionic solutes are strongly dependent on the buildup regime of the PEM films. This permeability can be modified by tuning the ionization degree of the polycations or polyanions, provided the film is made from weak polyelectrolytes. In most previous investigations, this was achieved by playing on the solution pH either during the film buildup or by a postbuildup pH modification. Herein we investigate the functionalization of poly(allylamine hydrochloride)/poly- (glutamic acid) (PAH/PGA) multilayers by ferrocyanide and Prussian Blue (PB). We demonstrate that dynamic exchange processes between the film and polyelectrolyte solutions containing one of the component polyelectrolyte allow one to modify its Donnan potential and, as a consequence, the amount of ferrocyanide anions able to be retained in the PAH/PGA film. This ability of the film to be a tunable reservoir of ferrocyanide anions is then used to produce a composite film containing PB particles obtained by a single precipitation reaction with a solution containing Fe 3þ cations in contact with the film. The presence of PB in the PEM films then provides magnetic as well as electrochemical properties to the whole architecture. Introduction The deposition of polyelectrolyte multilayer (PEM) films became a versatile and simple method to functionalize the surface of a broad range of materials in an easy and reproducible manner, allowing one to control the thickness of the film by playing on parameters such as the number of adsorption steps or the physicochemical parameters of the solution during the build-up of the film. 1-5 The deposition of these coatings relies on the overcompensation of the surface charge of the substrate upon the deposition of a polyelectrolyte, hence allowing the deposition of an oppositely charged one. 6-8 The successive deposition of two oppositely charged polyelectrolytes, separated by a rinsing step with a polyelectrolyte free solution, leads to a “layer pair”. The electrostatic interactions can be of very peculiar nature. 9 Indeed, it has been found that the complexation enthalpy between the polycation and the polyanion used to build up the PEM films is endothermic when the buildup regime of the film is supralinear. This means that the interactions between the participating poly- electrolytes are driven by an entropy increase. 9 In has also been demonstrated that the interactions allowing the buildup of such films are not only of pure electrostatic nature. 10 The global entropy increase accompanying polyelectrolyte complexation is most probably due to counterion release, as it has been demon- strated for polycation-DNA complexation processes taking place in solution. 11 The absence of small ions originating from the electrolyte solution in PEM films made from poly- (diallyldimethyl ammonium chloride) (PDADMAC) and poly- (4-styrene sulfonate) (PSS) first suggested the intrinsic charge compensation model in which the charge of the polyanions is exactly matched by the charge of the polycations in the bulk of the film. 12 In the framework of this model, only the substrate-PEM film and PEM film-solution interfaces are charged. However, the charge compensation could also be of extrinsic nature, meaning that the ions from the electrolyte solution would contribute to the charge compensation of the PEM film. In this latter case, the PEM films should display a Donnan potential. 13 Cyclic voltammetry (CV) experiments performed on PEM films made from different combinations of polyanions and polycations have shown that such films can be either impermeable or permeable to multivalent redox probes. Linearly growing PEM † Part of the “Langmuir 25th Year: Self-assembled polyelectrolyte multilayers: structure and function” special issue. *Corresponding author. Phone: þ33 (0)3 90 24 32 58; fax: þ33 (0)3 90 24 33 79; e-mail: vincent.ball@medecine.u-strasbg.fr (V.B.). Phone: þ33 (0)3 88 41 40 12; e-mail: schaaf@ics.u-strasbg.fr (P.S.). (1) Decher, G. Science 1997, 277, 1232. (2) Bertrand, P.; Jonas, A.; Laschewsky, A.; Legras, R. Macromol. Rapid Commun. 2000, 21, 319. (3) Hammond, P. T. Curr. Opin. Colloid Interface Sci. 1999, 4, 430. (4) Sch€ onhoff, M. Curr. Opin. Colloid Interface Sci. 2003, 8, 86. (5) Ariga, K.; Hill, J. P.; Ji, Q. Phys. Chem. Chem. Phys. 2007, 9, 2319. (6) Caruso, F.; Donath, E.; M€ ohwald, H. J. Phys. Chem. B. 1998, 102, 2011. (7) Ladam, G.; Schaad, P.; Voegel, J.-C.; Schaaf, P.; Decher, G.; Cuisinier, F. J. G. Langmuir 2000, 16, 1249. (8) Buron, C. C.; Fili^ atre, C.; Membrey, F.; Perrot, H.; Foissy, A. J. Colloid Interface Sci. 2006, 296, 409. (9) Laugel, N.; Betscha, C.; Winterhalter, M.; Voegel, J.-C.; Schaaf, P.; Ball, V. J. Phys. Chem. B 2006, 110, 19443. (10) Kotov, N. A. Nanostruct. Mater. 1999, 12, 789. (11) Mascotti, D. P.; Lohman, T. M. Proc. Natl. Acad. Sci. U.S.A. 1990, 87, 3142. (12) Schlenoff, J. B.; Ly, H.; Li, M. J. Am. Chem. Soc. 1998, 120, 7626. (13) Calvo, E. J.; Wolosiuk, A. J. Am. Chem. Soc. 2002, 124, 8490. Downloaded via BIBCNRS INC on January 16, 2020 at 11:45:26 (UTC). 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