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.