Molecular orientation of poly(ethylene terephthalate) and buried interface characterization of TiO2 films on poly(ethylene terephthalate) by using infrared-visible sum-frequency generation

The surface molecular orientation of biaxially stretched poly(ethylene terephthalate) (PET) films and the buried interface between TiO2 layer and PET substrate have been investigated by using infrared-visible sum-frequency generation (SFG). The surface SFG spectra showed a pronounced peak at 1710 cm−1 which is characteristic of the CO stretching vibration in an ester function. The polymer chains at the surface appear to be well aligned. After deposition of a TiO2 layer on PET surface by using oxygen-radical beam assisted method, SFG spectra exhibited a band at 1688 cm−1, which suggests the formation of Ti–O–C bonds. Oxygen radical affects phenyl ring part and induces a ring-opening reaction.