Carbon dioxide plasticization of thin glassy polymer films

We have demonstrated in previous studies that thin glassy polymer films exhibit complex responses to highly sorbing penetrants, such as CO2, relative to their thick film counterparts. In this paper, we apply similar experiments to two new polymers, including a polysulfone made from bisphenol A (PSF), and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and compare their responses to Matrimid® to understand better CO2 plasticization behavior of these materials when in thin film form. As expected, the extent of plasticization response tracks with CO2 solubility; CO2 diffusivity may also be an important factor at shorter exposure times. Experiments at longer CO2 exposure times revealed that each polymer experiences the permeability maximum observed in our previous work as well. However, polymers that are not as highly sorbing to CO2, like polysulfone, may not at some conditions exhibit a distinct permeability maximum but will still decrease in permeability after a long period of CO2 exposure owing to physical aging.