Fourier transformation infrared (FT-IR) spectra were scanned from smooth polymer films with a thickness of 0.2 mm using a Nicolet 6700 FT-IR spectrometer (Nicolet, Madison, WI, USA) by the FT-IR attenuated total reflection (ATR) method. Ten scans at 4 cm−1 resolution were signal averaged and stored as data files for further analysis.