Structure and Core Electron Absorption Spectra of Polyester Films

Soft x-ray absorption spectra of oriented films of polyethylene terephthalate PET and polyethylene naphthalate (PEN) of several tenth micron in thickness were measured by a transmission method. A similar resolution and the same dependence on the beam incident angle as obtained by a total electron yield method were observed in the oxygen Kedge region, but not in the carbon K-edge. IR spectra of the thin oriented sample films utilized in these measurements indicated their aromatic rings to be parallel to the film plane as found in the thick PET and PEN films. This fact conformed to the spectral change near the oxygen K-edge and gave a further support of the peak assignments made previously. The spectral behavior near the carbon K-edge was interpreted by the saturation effect which was due to the presence of greater number of carbon atoms in a repeat unit than oxygen atoms, and partially by strayed light effects.