An improved time-resolved soft-pulse dynamic compression attenuated total reflection (ATR) step-scan Fourier transform rheo-optical system has been developed. This system was used to observe reversible dynamic responses of poly(ethyleneterephthalate) (PET) and poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) films. In the case of PET, reversible nonlinear dynamic responses were observed in the C=O stretching vibration. The nonlinear responses decreased with decreasing compressive strain from 0.045 to 0.018. For the C-O stretching bands associated with the backbone structure of the PET, the nonlinear responses were very small. Characteristic burst-like reversible nonlinear dynamic responses can be seen in the in-phase and out-of-phase C=O stretching vibrations of cyclic imides, and phenyl ring deformation bands in the PDA parts of the BPDA-PDA. The results suggest the presence of inter-molecular interaction between C=O of cyclic imides and the phenyl ring groups of the PDA parts. The present method shows promise for characterizing a wide variety of polymeric materials, including polymer alloys, blends, composites, and copolymers and semicrystalline polymers.
YUJI NISHIKAWA, TATSUHIKO NAKANO, and ISAO NODA, "Detection of Reversible Nonlinear Dynamic Responses of Polymer Films by Using Time-Resolved Soft-Pulse Compression Attenuated Total Reflection Step-Scan Fourier Transform Infrared Spectroscopy," Appl. Spectrosc. 66, 312-318 (2012)