Chemical structure of resulting copolyesters was also assessed using Fourier transform infrared (FTIR) spectroscopy (Fig. ). vibrations, respectively. The deformation and wagging vibrations of the methylene -CH2groups were identified by multibands appearing at 1417-1463 cm -1 and 1369-1398 cm -1 , respectively. Additionally, the in-plane and out-of-plane deformation vibrations of aliphatic C-H and C-C groups were represented by bands in the 1000-500 cm -1 region. It is worth mentioning that no significant differences were observed in the region 1700-500 cm -1 for the copolymer series, which is where the most important functional groups are found.