The Possibility of Obtaining Films by Single Sedimentation of Polyelectrolyte Complexes

Surface coatings obtained by a step-by-step (SBS) deposition process of polymers carrying mutually complementary moieties (like polycations and polyanions) allow for a versatile multifunctionalization of a vast kind of materials. However the SBS deposition process can be extremely time-consuming when it is performed by alternatively dipping the substrates in the solutions carrying the interacting species. There is hence an important need to obtain coatings of similar composition as those obtained in the SBS manner but in a "one pot" manner. Here we show that the sedimentation of stoichiometric polyelectrolyte complexes can lead to a homogeneous coating. This is possible if the polylectrolyte complexes display a high internal mobility. The film growth rate is then in direct relation with the sedimentation rate of its constituting complexes. On the other hand when the interactions between the oppositely charged polyelectrolytes are too strong, the obtained coating is neither continuous nor homogeneous.