title: Nanosized films based on multicharged small molecules and oppositely charged polyelectrolytes obtained by simultaneous spray coating of interacting species.
abstract: Simultaneous spraying of polyelectrolytes and small multicharged molecules of opposite charges onto a vertical substrate leads to continuous buildups of organic films. Here, we investigate the rules governing the buildup of two such systems: poly(allylamine hydrochloride)/sodium citrate (PAH/citrate) and PAH/sulfated α-cyclodextrin (PAH/CD-S). Special attention is paid to the film growth rate as a function of the spraying rate ratio of the two constituents. This parameter was varied by increasing the spraying rate of one of the constituents while maintaining constant that of the other. For PAH/CD-S systems, whatever the constituent (PAH or CD-S) whose spraying rate was kept fixed, the film growth rate first increases and passes through a maximum before decreasing when the spraying rate of the other constituent is increased. For PAH/citrate, the film growth rate reaches a plateau value when the spraying rate of citrate is increased while that of PAH is maintained constant, whereas when the spraying rate of citrate is maintained constant and that of PAH is increased, a behavior similar to that of PAH/CD-S is observed. The composition of PAH/CD-S sprayed films determined by X-ray photoelectron spectroscopy is independent of the spraying rate ratio of the two constituents and corresponds to one allylamine for one sulfate group. For PAH/citrate, by increasing the PAH/citrate spraying rate ratio, the carboxylic/nitrogen ratio in the film increases and tends to 1. There is thus always a deficit of carboxylic groups (COO(-) + COOH) with respect to amines (NH2 + NH3(+)). Yet, the ratio (COO(-)/NH3(+)) is always close to 1, ensuring exact charge compensation. The film morphology determined by atomic force microscopy is granular for PAH/CD-S and is smooth and liquid-like for PAH/citrate. A model based on strong (respectively weak) interactions between PAH and CD-S (respectively citrate) is proposed to explain these features.
authors.affiliation: Centre National de la Recherche Scientifique (CNRS), Institut Charles Sadron (UPR 22) , 23 rue du Loess, 67034 Strasbourg Cedex, France.
authors.forename: Mathias
authors.initials: M
authors.lastname: Lefort
authors.forename: Loïc
authors.initials: L
authors.lastname: Jierry
authors.forename: Fouzia
authors.initials: F
authors.lastname: Boulmedais
authors.forename: Karim
authors.initials: K
authors.lastname: Benmlih
authors.forename: Philippe
authors.initials: P
authors.lastname: Lavalle
authors.forename: Bernard
authors.initials: B
authors.lastname: Senger
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Voegel
authors.forename: Joseph
authors.initials: J
authors.lastname: Hemmerlé
authors.forename: Arnaud
authors.initials: A
authors.lastname: Ponche
authors.forename: Pierre
authors.initials: P
authors.lastname: Schaaf