Introduction of molecular scale porosity into semicrystalline polymer thin films using supercritical carbon dioxide

We report supercritical carbon dioxide (scCO(2)) technology used for forming a large degree of molecular scale porosity in semicrystalline polymer thin films. The following three steps were integrated: (i) pre-exposure to an organic solvent which melted crystalline structures but did not cause a decrease in thickness, (ii) scCO(2) exposure under the unique conditions where the anomalous absorption of CO(2) occurred, and (iii) subsequent quick evaporation of CO(2) to preserve the swollen structures. This unified process resulted in homogenous low-density polyphenylene vinylene films (a 15% reduction in density) with the sustained structure for at least 6 months at room temperature.