An ESCA study of the photo-oxidation of the surface of polystyrene film

The surface photo-oxidation of polystyrene film is examined using ESCA. The initial stage involves the formation, primarily, of CO groups on the surface. Further reaction produces carbonyl, carboxyl and carbonate groups, accompanied by the disappearance of the C_1s shake-up satellite peaks, indicating the photo-oxidation of the phenyl groups. The relative concentrations of these groups at the surface are followed as a function of oxidation time. The $\text{C}\text{O}$ peak intensity ratio indicates a limiting C:O stoichiometry in the surface of ～ 1·7:1, very different from the bulk of the polymer. Carboxyl groups predominate in this highly oxidised surface.