Consequences of sequential photooxidation of polycarbonate: Relating microscopic modifications to the change of oxygen permeability

Abstract

AbstractThe consequences of light‐induced oxidation of polycarbonate on its permeability to oxygen were deeply investigated. Polymer films were sequentially photoaged, resulting in the sequential appearance and growth of oxidation products at the surface of the exposed side up to a limit value, owing to the progressive yellowing of the film during the photoageing process. Such effect restricts drastically the oxidation process to the film surfaces. The observed decrease in oxygen permeability consecutive to exposure of only one side of the film results principally from a decrease in oxygen solubility into the polymer, with a minor reduction of its diffusion ability. This was explained by the increase of the polymer polarity owing to the appearance of several types of polar chemical groups (namely CO and OH) as well as the occurrence of cross‐linking upon photodegradation. This decrease in oxygen permeability is then a positive feature in the case of applications for packaging and medical components. No further decrease in oxygen permeability was observed when the second side of the films was photooxidized, which can be explained by a “funnel effect” type between sorption, diffusion and desorption steps.