Using nanoparticles to inhibit dewetting in thin polymer films for potential applications in chemical sensors

Thin polymeric films are used in many new and emerging technologies, including nanolithography resist layers, fuel cells, dielectric coatings and chemical and biological sensors. Successful use of these materials requires that they be continuous, of uniform thickness and remain stable on a variety of organic and inorganic substrates. However, polymer films above their glass transition temperature or plasticized through solvent absorption may dewet from a substrate. The stabilization of these films by addition of various nanoparticles such as fullerenes (C60) and polystyrene nanoparticles was investigated in this study. Previous researchers have shown that addition of fullerenes, dendrimers and polystyrene nanoparticles to thin polystyrene films (<50 nm) inhibits dewetting upon high temperature annealing. In this work the dewetting behavior of nanoparticle filled polymer films was investigated upon solvent annealing, similar to that seen in the manufacture and use of chemical sensors. It was found that under certain conditions the thin films were stabilized by the addition of a small amount of nanoparticles upon exposure to a solvent atmosphere just as they are stabilized during thermal annealing. This stabilization is due to the nanoparticles segregating to the substrate surface upon manufacture of the polymer film, forming a jammed state or gel-like network which makes the system stable. In addition, the effect of surface energy on the ability of nanoparticles to inhibit dewetting was investigated. In final studies, nanoparticle-filled polymer films were used in live sensors where the reliability and robustness were studied.