Time-resolved FTIR/FTNIR spectroscopy: Powerful tools to investigate diffusion processes in polymeric films and membranes

Abstract

The application of time-resolved FTIR spectroscopy to investigate diffusion processes in polymers is described. Two thermosetting systems have been studied: a tetrafunctional epoxy resin cured with an aromatic diamine hardener, and a ternary formulation comprising the above components plus a bismaleimide co-monomer. Spectroscopic monitoring of water diffusion, both in the Mid and in the Near IR frequency ranges, yielded accurate and reproducible kinetic curves from which it was possible to evaluate the absolute parameters of diffusion (diffusivity and activation energy). These were found to compare favourably with the values obtained by conventional gravimetric methods. The molecular interactions between the penetrant molecules and the polymer networks were also investigated and it was shown that, in the system containing the bismaleimide component, the fraction of water molecules hydrogen-bonded to the network decreases significantly.