Abstract: Disclosed is a method and apparatus that contacts polymers with supercritical fluids in a density fluctuation ridge, producing selectively porous low-density regions impermeable to large molecule gases, for use in gas masks and respiratory processes.

Abstract: A method for forming a polymer film with improved physical properties and films formed by the method. The method includes contacting a polymer film with a supercritical fluid, preferably supercritical carbon dioxide or supercritical ethane, at high pressure and high temperature conditions which correspond to the density fluctuation ridge conditions of the supercritical fluid. The films formed by this method have a lower density, a reduced glass transition temperature, an increased nanoscale-porosity, a decreased dielectric constant and increased adhesion to a metallic layer.