The effect of carbonyl group on sorption of CO2 in glassy polymers

The interaction of CO2 and polymers was investigated by examining the sorption isotherms and the desorption time variation of characteristic IR absorption bands. From the time variation of the bending mode (ν2) of CO2 at near 660 cm−1 and the antisymmetric stretching mode (ν3) of CO2 at near 2340 cm−1, the CO2 within the polymer film containing carbonyl groups (e.g. poly(methyl methacrylate) (PMMA)) was much more difficult to outgas than the polymer film containing phenyl rings (e.g. polystyrene (PS)). From the red shift of the stretching mode of carbonyl groups at near 1740 cm−1 for the PMMA film upon CO2 treatments, the bonding force of the carbonyl group–CO2 interaction is much weaker than that of the conventional hydrogen bonding and Lewis acid–base interaction. The CO2 was surprisingly found to be present within PMMA for about 6 months after CO2 treatments as demonstrated by the shifting of loss maxima of dynamic mechanical analyses (DMA) toward low temperatures.