On the determination of carbon sp2/sp3 ratios in polystyrene–polyethylene copolymers by photoelectron spectroscopy

Abstract A series of monodisperse polystyrene/polyethylene tapered block copolymers, with known carbon sp2/sp3 ratios, was evaluated by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The principal component of the C1s peak exhibited no useful variation in shape as the sp2 concentration was varied. The valence band spectra, however, were found to vary in a systematic manner with the sp2 concentration. This variation was reflected in the X-ray excited C KLL Auger peak, the structure of the Auger peak providing a ready characterization of the carbon sp2 concentration. The problem of determining the sp2/sp3 ratio in hydrogenated amorphous carbon is discussed.