Specific Intermolecular Interaction of Carbon Dioxide with Polymers

Fourier transform IR spectroscopy has been used to investigate the interaction of carbon dioxide with polymers. IR transmission and attenuated total reflectance spectra were obtained for CO 2 impregnated into polymer films. It has been shown that the polymers possessing electron-donating functional groups (e.g., carbonyl groups) exhibit specific interactions with CO 2, most probably of Lewis acid−base nature. An unusual aspect is the use of the bending mode (ν 2 ) of CO 2 to probe polymer−CO 2 interactions. The evidence of the interaction is the observation of the splitting of the band corresponding to the CO 2 ν 2 mode. This splitting indicates that the double degeneracy of the ν 2 mode is removed due to the interaction of electron lone pairs of the carbonyl oxygen with the carbon atom of the CO 2 molecule. This splitting has not been observed for polymers lacking electron-donating functional groups (e.g., poly(ethylene)). In contrast, the ν 3 mode shows little if any sensitivity to this interaction, which is in accordance with the interaction where CO 2 molecule acts as an electron acceptor. Finally, the chemical and engineering implications of this type of specific interaction of CO 2 with polymers are discussed; perhaps the changes in spectra of CO 2 incorporated into polymers might serve as a basis for prediction of the solubility of CO 2 in polymers.