Engelbrecht, Sebastian and Pichot, Vincent and Goepfert, Thomas and Lin, Hungyen and Fischer, Bernd M. (2022) Extraction of Fickian water diffusion in polymers using terahertz time-domain spectroscopy. Polymer, 257: 125285. ISSN 0032-3861
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Abstract
The dynamic behavior of polycarbonate and poly(methyl methacrylate) upon water immersion at temperatures of 40 °C and 70 °C was studied by gravimetric measurements and by terahertz time-domain spectroscopy. Time-resolved measurements of the terahertz refractive index and absorption coefficient show a good agreement to the gravimetric measurements. Assuming a Fickian diffusion mechanic the diffusion coefficients were extracted from both methods. It was found that the terahertz measurements provide a reliable non-contact way to study the water diffusion in polymers. Especially, the THz absorption coefficient seems to be a robust method to determine the diffusion coefficients.