Molecular Interactions in and Transport Properties of Densely Cross-linked Networks: A Time-resolved FTIR Spectroscopy Investigation

Transport of water in an epoxy network with high cross-link d. was investigated at several water vapor activities by time-resolved FT-IR spectroscopy and gravimetric measurements. The anal. of the IR spectra provided information about the mol. interactions occurring in the system. In particular, several interaction complexes were identified and their structures were proposed. An est. was made of the concn. of the various water species present in the system, based on the knowledge of the resp. molar absorptivities. An excellent agreement between the spectroscopic and gravimetric detns. of sorbed water was found throughout. The evolution of the different water species was monitored by resolving the complex profile of the water spectrum in the nOH frequency range. This information, coupled with the results of the gravimetric anal., was used to evaluate the effect of polymer/penetrant H-bonding interactions on the diffusion process of water mols. Transport of the different water species was found to follow a Fickian behavior characterized by an effective diffusion coeff. which increases with total water concn.