(629f) “Exponential” Layer-by-Layer Polymer Films for Loading and Assembly of Nanoscale Materials

Layer-by-layer (LBL) assembly advancement has recently been used for the fabrication of multilayer polymer films whose thicknesses increase exponentially. The exponential films provide the ability for loading of active molecules after the preparation of LBL polymer films. The significance of finding a unique approach to reversibly load-and-unload CdTe nanoparticles (NPs) in an already prepared LBL film was shown previously. So, an essential area to understand is whether the use of the fast growth rate of exponential-LBL is possible for one dimensional (1D) inorganic nanoscale materials, such as nanowires and, nanotubes, which exhibit a definite degree of mobility/flexibility similar to rod-like polymers. To demonstrate we used exponentially growing LBL films made from poly(diallyldimethylammonium chloride) (PDDA) and polyacrylic acid (PAA). Different dispersions of carbon nanotubes (CNTs) and CdTe nanowires kept in contact to the polymer films showed high swelling for CNTs and no swelling for the CdTe nanowires. Scanning electron microscopy (SEM) and conductivity measurements at different time intervals clearly indicate the insertion of CNTs in the LBL films. A series of studies showed CNTs and CdTe NWs showed different diffusion rates in the polelectrolyte films depending upon the rigidity and surface charge of the materials. The idea for introducing long 1D CNTs and CdTe NPs was also extended as the path to first introduce NPs in the LBL films and then mobility of the NPs inside the polymeric matrix was used for the in-situ self-assembly of NPs for nanowire formation.