Green thin polymer film metallization using supercritical carbon dioxide

It is shown that low-density polymer layers created by supercritical carbon dioxide (scCO2) processing can be exploited to enhance metallization of thin polymer films. Spun-cast thin films were exposed to scCO2 within the narrow temperature and pressure regime known as the `density fluctuation ridge', where excess swelling of the polymer thin films was induced, and the swollen structures could be subsequently preserved by quick evaporation of CO2. X-ray reflectivity (XR) measurements proved that the `expanded' films had a broader interfacial width between the polymer and deposited metal layers, regardless of the polymer film thickness or choice of polymers. Furthermore, standard peel test showed a drastic enhancement in adhesion between the polymer and metal layers, which correlates with the XR result: the broader interfacial width indicates increased adhesion.