Three-dimensional orientation change during thermally induced structural change of oriented poly(trimethylene terephthalate) films using polarized FTIR–ATR spectroscopy

The three-dimensional orientation change during thermally induced structural change was monitored in a ‘real-time’ mode with polarized FTIR–ATR spectroscopy using a double-edged parallelogram crystal in a temperature-controlled ATR set-up. Upon cold-crystallization of stretched PTT sample, the growth of crystalline phase along the stretching direction was much faster than those along the perpendicular directions. The cold-crystallization of melt-quenched amorphous PTT was found to produce crystallites of no orientation, as expected. The formation of crystalline phase along three orthogonal directions was followed by changes of three attenuation indices of 1358 cm^?1 band which is associated with the wagging vibration motion of CH₂ groups in crystalline phase. The orientation of CH₂ groups in amorphous phase estimated from three attenuation indices of 1385 cm^?1 band along three directions was very small even for the cold-crystallized, anisotropic PTT sample. This work appears to be the first successful observation in a ‘real-time’ mode on the dynamic change of three-dimensional orientation of polymeric materials using temperature-controlled polarized FTIR–ATR spectroscopy.