Yuji Nishikawa

Two-Dimensional Correlation Study of Uniaxially Drawn Poly(Ethylene Terephthalate) Films by Using Attenuated Total Reflection Based Dynamic Compression Modulation Step-Scan Fourier Transform Infrared in Combination with Spectral Simulation Analysis by Density Functional Theory

Attenuated total reflection (ATR) based dynamic compression modulation two-dimensional (2D) correlation studies of uniaxially drawn polyethylene terephthalate) (PET) films have been performed in combination with spectral simulation analysis by density functional theory (DFT). The dynamic 2D infrared (IR) correlation spectra in the region of the CCO stretching mode vibrations show four distinct correlation peaks located around 1290, 1265, 1248, and 1234 cm−1. These bands can be clearly assigned to the combination bands or coupling modes of the CH in-plane bend of the benzene ring or the CH2 deformation of the ethylene glycol unit, as well as CCO stretching vibrations, which are gauche conformers characteristic bands, by DFT analysis. The sequential analysis of 2D correlation data shows that, upon applying the dynamic compression, the response of the side chain regions (ester groups) occurs first, followed by that of the backbone regions (benzene rings). The ATR based dynamic compression modulation 2D correlation spectroscopy in combination with DFT analysis can be a powerful tool for various polymer characterizations.

Two-dimensional correlation analysis of polyimide films using attenuated total reflection-based dynamic compression modulation step-scan Fourier transform infrared spectroscopy.

Attenuated total reflection (ATR)-based dynamic compression modulation two-dimensional (2D) correlation study of poly(p-phenylene biphenyltetracarboximide) film is carried out in combination with spectral simulation analysis by density functional theory (DFT). The dynamic 2D infrared (IR) correlation spectra in the region of imide I (C=O stretching mode) show three distinct correlation peaks located around 1777, 1725, and 1708 cm−1. The band at 1708 cm−1 is the lower wavenumber shift component of 1777 or 1735 cm−1 peaks and is attributed to the results from intermolecular interactions, according to the DFT analysis. The 1708 cm−1 band also shows the largest dynamic response, suggesting that these intermolecular interactions may enhance the dynamic response. The dynamic 2D IR correlation spectra in the region of imide II (C–N–C axial stretching mode) vibrations also show three correlation peaks located around 1335, 1355, and 1370 cm−1, although the imide II band is shown to consist substantially of one component by the DFT analysis. These multiple peaks may be attributed to the compression-induced wavenumber shift of the band in the backbone structures. The sequential analysis of 2D correlation data show that, upon applying the dynamic compression, the response of the backbone regions (imide II) occurs first, followed by that of the side-chain regions (imide I, C=O).

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

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.

Rheo-optical study of polymers by using time-resolved soft-pulse compression attenuated total reflection step-scan Fourier transform infrared spectroscopy.

A 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 different viscoelastic properties of polyethyleneterephthalate (PET) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx). Resonance features were observed in the dynamic compression ATR spectrum of PHBHx with 625 Hz soft-pulse frequency. In contrast, the dynamic compression ATR spectrum of PET showed no resonance features. The resonance feature of PHBHx was found at 1723 cm−1, which corresponds to the structural or morphological reorganization of a less ordered (Type II) crystalline form under compressive perturbation. The time-resolved evolution of infrared (IR) spectra was effectively analyzed by conventional generalized two-dimensional (2D) correlation analysis. The 2D-IR results indicate that the dynamic response of the well-ordered Type I crystalline state (1289 and 1261 cm−1) is faster than that of the Type II (1723, 1277, and 1228 cm−1). The present method shows promise for characterizing a wide variety of viscoelastic materials, including polymer alloys, blends, composites, and copolymers, and semicrystalline polymers.

Impulse-Induced Compression Rheo-Optics Study of Polymers Using Attenuated Total Reflection Based Step-Scan Fourier Transform Infrared Time-Resolved Spectroscopy

An impulse-induced attenuated total reflection (ATR) based dynamic compression step-scan time-resolved Fourier transform rheo-optical system has been developed. This system was used to observe different viscoelastic properties of poly(ethylene terephthalate) (PET), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx), and carbon-black-filled polyester-polyamide blend. In the case of PET, almost no viscoelastic response extending beyond 15 ms was observed in the dynamic absorbance difference time domain spectrum. In contrast, PHBHx showed apparently different viscoelastic responses in the dynamic absorbance difference spectrum, especially in the C=O stretching band region. A long relaxation tail of the 1723 cm−1 band lasting about 2.7 milliseconds was clearly seen. The tail corresponds to the structural or morphological reorganization of a less ordered crystalline form (Type II) under compressive perturbation. The carbon-black-filled polyester–polyamide blend film also shows different viscoelastic response tails. In this case, the amide C=O stretching vibration band does not show distinct viscoelastic responses, suggesting that the polyamide component does not contribute much to the viscoelastic properties. The present method shows promise for characterizing a wide variety of viscoelastic materials, including polymer alloys, blends, composites, copolymers, and semicrystalline polymers.