Surface characterization and photochemical behavior of poly(ethylene terephthalate) and TiO_2/poly(ethylene terephthalate) interface by using sum-frequency generation

摘要

The surface moleuclar orientation, buried interface characterization of biaxially stretched poly(ethylene terephthalate) (PET) film, and its photochemical behavior by UV irradiation have been investigated by using infrared-visible sum-frequency generation (SFG). The SFG spectra of PET surface showed a pronounced peak at 1705 cm~(-1) which is characteristics of the C=O stretching vibration in an ester function. The SFG spectra indicate that the polymer chains at the surface appear to be well aligned parallel to the surface plane. By depositing a TiO_2 film, the C=O and the C=C bonds of PET are tilted from the surface plane. Change of the molecular orientational conformation distribution is also observed inthe case of TiO_2/PET interface. In contrast to the case of TiO_2/PET, deposition of SiO_2 film on PET surface does not induce changes in the molecular orientational conformation. By irradiating UV pulses, photo-degradation of PET is observed for TiO_2/PET interface, while such degradation is not observed in PET surface and SiO_2/PET interface.