A Hyphenated Approach Combining Pressure-Decay and In Situ FT-NIR Spectroscopy to Monitor Penetrant Sorption and Concurrent Swelling in Polymers

A new hyphenated technique based on simultaneous in situ FT-NIR spectroscopy and pressure-decay measurements has been implemented to study sorption of low-molecular-weight compounds in polymeric membranes and the induced swelling of the matrix. The FT-NIR measurements are performed in the transmission mode and, besides sorption equilibrium and kinetics, allow also the straightforward measurement of polymer swelling. The pressure decay method is used to provide quantitative information on the concentration of penetrant sorbed in the polymer. This measurement, once combined with the photometric data, allows an accurate estimation of the molar absorptivity of the analytical peaks as well. To validate the new experimental approach, sorption of CO2 in polydimethylsiloxane at 35 degrees C and at pressures up to 9 bar has been investigated and the results are compared with available literature data.

Automated summary

A new hyphenated technique combining in situ FT-NIR spectroscopy and pressure-decay measurements has been implemented to study sorption in polymeric membranes. The method allows for accurate estimation of the molar absorptivity of analytical peaks by combining photometric data with quantitative information from pressure decay measurements. The experimental approach was validated by investigating CO2 sorption in polydimethylsiloxane and comparing the results with existing literature data.