Nanoparticle assembly in polymer thin films and polymer melts.

摘要

The assembly of nanoparticles in polymeric materials has drawn great attention, due to its extraordinary potential for a variety of nano-scale applications. In this work, we first investigated the assembly of nanoparticles to interfaces in polymer thin films, as well as with the presence of large subjects on the substrate. According to cross-sectional transmission electron microscopy (TEM) images, it was found that pyridine stabilized cadmium selenide nanoparticles assemble on the substrate and also along large subjects such as silica particles or nanotubes, after being thermal annealed above the glass transition temperature of the polymer. The assembly of nanoparticles is driven by the interplay between entropic and enthalpic forces, which dictate their assembly direction in polymer thin films. Remarkably, even when film thicknesses were reduced to be thinner than the surface subject sizes, the films followed the curved features instead of dewetting from the substrate, indicating very strong assembly energy. We demonstrated these three-dimensional surfaces through atomic force microscopy (AFM). Finally, we explored the assembly of nanoparticles in polymer melts with the presence of large silica particles and found that nanoparticle assembly around the silica particles increased with longer annealing time. This is because once the nanoparticles diffuse in the polymers and reach the surfaces of silica particles, they adhere on the curved surfaces due to entropic forces.