Investigation for defect formation in nanoparticles/polymer composite thin films coated on a solid surface

Abstract

In this work, dewetting of inorganic nanoparticles/polymer composite thin films, which are notable materials in various fields, has been investigated experimentally. Here, CeO₂ nanoparticles surface-modified with oleic acid and polystyrene （PS） were used as nanoparticles and polymer, respectively. The CeO₂ nanoparticles were synthesized by organic-ligand-assisted supercritical hydrothermal synthesis by Adschiri et al., and consequently, can be sufficiently dispersed in organic solvent and polymers. In experiment, a PS thin film with CeO₂ nanoparticles spun-coated onto a silicon substrate was heated at 393 K, and then dewetting phenomena of the thin film was observed using an optical microscope. As a result, the dewetting was suppressed by adding 0.4 wt ％ CeO₂ nanoparticles with respect to PS, and was perfectly inhibited with 1 wt％ CeO₂ nanoparticles. However, addition of 5 wt％ nanoparticles causes reoccurrence of dewetting in PS thin films. The interaction energy of polymer thin films with and without nanoparticles was estimated to consider the reason of inhibition of dewetting in the polymer thin film with nanoparticles.