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Polyelectrolyte multilayer (PEM) films present a versatile surface functionalization method allowing to address many applications. These coatings suffer; however, from weak mechanical properties this problem can be addressed by the regular incorporation of clays in the layering process. To allow for an even better control of a whole set of film properties, among them their thermal stability, their stability in water, and their impermeability to anions, we postmodify (PAH-MMT) films with polydopamine, by putting the pristine PEM films in contact with an oxygenated dopamine solution. This straightforward treatment allows to totally suppress the diffusion of hexacyanoferrate anions in the films and affects significantly its mechanical properties even, if the distribution of polydopamine through the film thickness is not yet known. [ABSTRACT FROM AUTHOR]

The modification of solid-liquid interfaces with polyelectrolyte multilayer films appears as a versatile tool to confer new functionalities to surfaces in environmentally friendly conditions. Indeed such films are deposited by alternate dipping of the substrates in aqueous solutions containing the interacting species or spraying these solutions on the surface of the substrate. Spin coating is more and more used to produce similar films. The aim of this short review article is to provide an unifying picture about the deposition mechanisms of polyelectrolyte multilayer films. Often those films are described as growing either in a linear or in a supralinear growth regime with the number of deposited "layer pairs". The growth regime of PEM films can be controlled by operational parameters like the temperature or the ionic strength of the used solutions. The control over the growth regime of the films as a function of the number of deposition steps allows to control their functional properties: either hard and impermeable films in the case of linear growth or soft and permeable films in the case of supralinear growth. Such different properties can be obtained with a given combination of interacting species by changing the operational parameters during the film deposition. [ABSTRACT FROM AUTHOR]

Surface coatings obtained by a step-by-step(SBS) deposition process of polymers carrying mutually complementarymoieties (like polycations and polyanions) allow for a versatile multifunctionalizationof a vast kind of materials. However the SBS deposition process canbe extremely time-consuming when it is performed by alternativelydipping the substrates in the solutions carrying the interacting species.There is hence an important need to obtain coatings of similar compositionas those obtained in the SBS manner but in a “one pot”manner. Here we show that the sedimentation of stoichiometric polyelectrolytecomplexes can lead to a homogeneous coating. This is possible if thepolylectrolyte complexes display a high internal mobility. The filmgrowth rate is then in direct relation with the sedimentation rateof its constituting complexes. On the other hand when the interactionsbetween the oppositely charged polyelectrolytes are too strong, theobtained coating is neither continuous nor homogeneous. [ABSTRACT FROM AUTHOR]

Abstract: The present article focuses on the influence of the salt concentration as well as on the influence of the nature of the salt on the deposition of (PAH-PSP) n films in the case where PSP is made from only 24 monomer units on average. The two main messages of this article are that: (i) for salt concentrations lower than about 0.2M, the film thickness increases linearly with the number of adsorption cycles after the deposition of a coating with a critical thickness necessary to prime the deposition of the film. In addition, for salt concentrations lower than 0.2M, there is no effect of the influence of the supporting electrolyte on the film thickness but a marked influence on the film composition as revealed from XPS measurements. (ii) For salt concentrations higher than about 0.2M, the films are extremely rough, and we demonstrate that the use of a homogeneous and isotropic model is not suited anymore to calculate the film thickness and its refractive index from the measured ellipsometric angles. Finally we try to rationalize all the data obtained so far on the (PAH-PSP) n films on the basis of counterion condensation of Na+ cations on the PSP chains. [Copyright &y& Elsevier]

Abstract: The deposition of polyelectrolyte multilayer films consists of the sequential adsorption of polycationic and polyanionic species at solid–liquid interfaces. The adsorption process can be performed either by alternated dipping of the substrate to be coated in the polyelectrolyte containing solutions, by alternated spin coating of these solutions or by alternated spraying of them. Different coating technologies can lead to different properties of the obtained coatings even for the same combination of polycations and polyanions. The aim of this article is to show that by playing on the concentration of the supporting electrolyte, NaCl, the films obtained by alternated spraying and alternated dipping grow differently and display different properties, in terms of refractive index, surface morphology, wettability for water and surface composition. [Copyright &y& Elsevier]

Abstract: Compact and linearly growing polyelectrolyte multilayer films have been used to suppress desorption of drugs, nanoparticles or proteins from underlying polyelectrolyte multilayer films as well as to significantly change their mechanical properties. The polyelectrolyte based capping layers are however cumbersome to deposit and alternative barrier layers offering enzymatic retention in the films as well as permeability to small molecules, for example the substrates of the embedded enzymes, are highly desired. In this article we show that barrier layers made through atmospheric pressure dielectric barrier discharge polymerization of ethylene glycol dimethacrylate offer the opportunity to simultaneously suppress enzyme desorption from the underlying polyelectrolyte multilayer film and to ensure accessibility of the enzymatic substrate. This holds true when the barrier film totally covers the underlying film and as long is not too thick. When the plasma deposited barrier becomes 300nm thick, the hydrolysis curve of the enzyme presents a lag phase typical of a diffusion-limited process. [Copyright &y& Elsevier]

Abstract: The deposition of polyelectrolyte multilayer films (PEMs) appears more and more as a versatile tool to functionalize a broad range of materials with coatings having controlled thicknesses and properties. To increase the control over the properties of such coatings, a good knowledge of their deposition mechanism is required. Since Cohen Stuart et al. (Langmuir 18 (2002) 5607–5612) showed that the adsorption of one polyelectrolyte could induce desorption of polyelectrolyte complexes instead of regular deposition, more and more findings highlight peculiarities in the deposition of such films. Herein we demonstrate that the association of sodium polyphosphate (PSP) as the polyanion and either poly(-L-lysine hydrobromide) (PLL) or poly(allylamine chloride) (PAH) as the polycations may lead to non-monotonous film deposition as a function of time. Complementary, films containing PSP and PLL can be obtained from a (PLL–HA) n template films after the exchange of HA (hyaluronic acid) from the sacrificial template by PSP from the solution. This exchange is accompanied by pronounced film erosion. However, when starting from a (PAH–HA) n template, the film erosion and exchange due to the contact with PSP is by far less pronounced, nevertheless the film morphology changes. These findings show that the nature of the polycation used to deposit the PEM film may have a profound influence of the film’s response to a competing polyanion. [Copyright &y& Elsevier]