The Fourier transform infrared spectrum of these films was obtained using an attenuated total reflectance-Fourier transform infrared (ATR-FT-IR) spectrometer (Perkin Elmer, Spectrum two, IL, USA). The spectrum was recorded over a wave range of 4000 cm-1 to 400 cm-1. The interference of water and CO2 from air wasdeducted during scanning.