Spectroscopic studies of the diffusion of water and ammonia in polyimide and polyimide-silica hybrids

Mass transport of low mol. wt. penetrants in polyimide and silica/polyimide hybrids has been investigated using time-resolved FTIR spectroscopy and gravimetric anal. In particular, transport of reacting (ammonia) and non-reacting (water) penetrants has been studied as a function of penetrant concn., evidencing peculiar features related to the presence of the inorg. phase in the hybrid systems. For the case of water, diffusivity and sorption equil. have been evaluated in an activity range between 0.1 and 0.75. Free water as well as mol. aggregates have been detected in both systems. In the case of ammonia, its reactivity with polyimide has been directly obsd., and the reaction mechanism elucidated. Furthermore, it has been possible to discriminate diffusion and reaction phenomena due to the different time scales of the two processes.