(164c) Nanoscale Reversible Loading and Unloading In Layer-by-Layer “Exponential” Polymer Films

Layer-by-layer (LBL) films have been shown in most of the studies for loading of active molecules only during the preparation by using the species of interest as active constituents in the film build up. The significance of finding a unique approach to reversibly load-and-unload nanoparticles (NPs) in an already prepared LBL films is four-fold. (a) It would enable fast and universal preparation of NP-based coatings with a variety of functionalities. (b) NPs mobility inside the polymeric matrix would allow new methods for self-assembly processes. (c) Dynamic exchange process is essential in the advancement of fine separation tools for NPs. (d) Last but not the least, to create important opportunities for biomedical applications using organic/inorganic nanocolloids, proteins, DNA, RNA, etc. in controlled-release devices. In this study we demonstrate that exponentially-growing LBL films have the ability to load/unload semiconductor NPs or other nanoscale species in a controlled fashion. To demonstrate this we used exponentially growing LBL films made from poly(diallyldimethylammonium chloride) (PDDA) and polyacrylic acid (PAA). As prepared (PDDA/PAA)n films, were exposed to a CdTe suspension (~ 4 nm). Release of the incorporated CdTe and reproducibility was demonstrated by immersing the CdTe-loaded films in pure water at pH = 9. The variations of the structure of the LBL layers (capping/topping layer), pH of water and the charge on NPs can be used to control the incorporation and release of the NPs making possible sensing, protective, biological, and optoelectronic functionalities. The similar procedure was also demonstrated for the loading of SWNT and nanorods.