Transport of Low Molecular Weight Compounds in Silica/Polyimide Hybrids

Mass transport of low-mol.-wt. penetrants in polyimide and SiO2/polyimide hybrids was studied by using time-resolved FTIR spectroscopy coupled with gravimetric anal. to gather information on the mobility and state of the sorbed penetrants and on phys. and chem. interactions between the penetrants and the matrixes. In particular, transport of reactive (NH3) and nonreactive (water) penetrants was studied as a function of penetrant concn., evidencing peculiar features related to the presence of the inorg. phase in the hybrid systems. In the case of NH3 it was possible, by proper selection of sample thickness and penetrant pressure, to discriminate diffusion and reaction phenomena due to the different time scales of the 2 processes. For the case of H2O, diffusivity and sorption equil. were evaluated in the activity range between 0.1 and 0.75. The states of H2O mols. are discussed from a simplified H-bonding assocn. model.