Selective sorption of nanoporous poly(methyl silsesquioxane)

The sorption behavior of nanoporous poly(methyl silsesquoxane), PMSSQ, thin films was investigated using a quartz crystal microbalance (QCM) combined with reflectance infrared spectroscopy (IR). The nanoporous PMSSQ films are intrinsically hydrophobic and show highly selective sorption behavior. With organic liquids having surface tensions below the critical value (38-48 dyn/cm), the extent of sorption increased with porosity of PMSSQ films. Extremely low amounts of sorption were measured with liquids having a surface tension higher than the critical value. The selective sorption behavior can be interpreted by capillary condensation resulting from the lowered vapor pressure in the nanoscopic pores.