Controlling cellular morphology by supercritical carbon dioxide

Abstract

AbstractA series of high‐performance porous materials, including open‐cell and closed‐cell foams, were prepared by a two‐stage batch foaming process from fluorinated poly(arylene ether)s, and the porous morphology was characterized with scanning electron microscopy. The effects of saturation pressures, saturation temperatures, transfer times, molecular structures, and solvent traces on the cell sizes, cell densities, and bulk densities of porous materials were examined. According to the conclusions, the porous structures could be controlled with cellular sizes between the nanoscale and microscale. All nanoporous materials have dielectric constants in the ultralow‐dielectric‐constant range (1.4–2.0). The open structures can be prepared by two methods, and there are two kinds of morphologies from the two methods, including foams with small, spotlike openings (diameters between 10 and 100 nm) in the cell walls and bicontinuous nanoporous foams. Another special method for controlling the porous morphology was used here. Films with closed‐cell microcellular foams were placed in supercritical carbon dioxide again. The original morphology of the microcellular foam collapsed. The collapsed morphology was also characterized with scanning electron microscopy, and three kinds of cellular morphology were observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009