The FT-IR studies of the interactions of CO2 and polymers having different chain groups

A Fourier transform-infrared spectroscopy (FT-IR) set up has been successfully modified in order to characterize different polymeric materials under sub- and supercritical CO2 conditions. Polymers used in this study are polyesters (P120 and P130), poly(ethylene glycol) (PEG) and polyphenylene oxide (PPO). Analysis of the corresponding spectra shows evidences of weak interaction (Lewis acid–base) between CO2 and polymers. In particular, shifts to higher wavelengths of the maximum absorption of chain groups of the polymer and the modification of the absorption band of CO2 represent a qualitative evidence of such interactions. Analysis of CO2 absorption bands allowed ranking of the polymeric materials according to interaction strength with CO2. In general, polymers with ether group display higher interaction strength than polyesters. The effect of the dissolved CO2 on the depression of the melting point, Tm or the glass transition temperature, Tg can also be studied using the FT-IR depending on the enhancement in the free volume. The shape of the spectrum in PEG, unlike the other polymers, was completely modified above the critical pressure (7.38 MPa).