Effect of particles on the structure of solvent-annealed block copolymer/nanoparticle composite thin film

The structure of nanocomposite thin films composed of polystyrene-b-poly(2 vinylpyridine)/Au nanoparticles (PS-PVP/Au) during chloroform vapor annealing was investigated. Our results revealed that the morphology of these composites depends on particle size and volume fraction. During solvent annealing, particles segregate to both polymer/substrate and air/polymer interfaces. The segregation of particles to the polymer/substrate interface balances the preferential interaction of two domains to the substrate, resulting in the transition of ordered domains from parallel to normal to the substrate. The introduction of large particles facilitates the segregation of particles to the top of the film. When the volume fraction of segregated particles is high, particles are repelled from the preferred domains to form particle-rich regimes. The wetting behavior of a thin film could be improved by the presence of nanoparticles. Our results showed that small particles provide the better ability to prevent thin film from dewetting.