Multilayer Films by Spraying on Spinning Surface--Best of Both Worlds

The layer-by-layer buildup of poly(styrene sulfonate), poly(diallyldimethyl ammonium) and/or TiO2-nanoparticles was carried out using an automated system which allowed spraying the polyion solutions on a spinning substrate. The different spraying and spinning arrangements were studied. The films were prepared by varying ionic strength, electrolyte species (NaBr and NaF) and spraying time. The results were compared to the films prepared by using the traditional dipping method. Depending on the electrolyte and the ionic strength the thickness of the films prepared with spraying on spinning substrate was thinner than or equal to the dipped films. It was found that addition of salt on spraying solutions is necessary in order to prepare thin films with a good quality. Spraying on spinning substrate generated evenly occupied smooth surfaces. The benefits of the automated method are attributed to the noticeably lower solution consumption and to the fact that the film deposition process could be accelerated by a factor of 100 comparing to the traditional dipping method.