Abstract-Terahertz spectroscopic analysis of crystal growth in poly(ethylene naphthalate)

Daisuke Odaka,  Yoshimichi Ohk, 


http://iopscience.iop.org/article/10.7567/JJAP.56.072401

Terahertz absorption spectra and X-ray diffraction patterns were measured for amorphous poly(ethylene naphthalate) (PEN) while the sample temperature was elevated from 25 to 230 °C then lowered back to 25 °C. Before the elevation of the temperature, PEN exhibited broad absorption with a maximum at around 2.6 THz. This absorption seems to originate from amorphous regions. As the sample temperature increases, PEN becomes crystallized in the form of α crystal. With this change in crystallinity, the 2.6 THz absorption becomes smaller, while another absorption peak at 2.05 THz, originating from crystalline regions, becomes larger. Furthermore, in the cooling process to 25 °C, the 2.05 THz absorption shifts to 2.15 THz and the lattice constants associated with this absorption become smaller. Therefore, intermolecular vibrations closely related to the crystal growth in PEN at high temperatures seem to be responsible for the THz absorption.

Abstract-Terahertz spectral change associated with glass transition of poly-ε-caprolactone

Marina Komatsu^1,a), Maya Mizuno², Shingo Saito³, Kaori Fukunaga² and Yoshimichi Ohki^1,4,b)
http://scitation.aip.org/content/aip/journal/jap/117/13/10.1063/1.4916746
1 Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo 169-8555, Japan
2 Applied Electromagnetic Research Institute, National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
3 Advanced ICT Research Institute, National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
4 Research Institute for Materials Science and Technology, Waseda University, Shinjuku, Tokyo 169-8555, Japan


a) mkomatsu@toki.waseda.jp
b) yohki@waseda.jp
J. Appl. Phys. 117, 133102 (2015); http://dx.doi.org/10.1063/1.4916746

We measured absorption spectra of unidirectionally stretched poly-ε-caprolactone (PCL) film in a range from 0.3 to 3.6 THz at temperatures from 10 to 300 K. Several absorption peaks were observed, when the electric field of THz waves was set in directions parallel and perpendicular to the stretching direction. The absorption bandwidths became significantly broad at around 200 K and above at least in two specific peaks. This temperature is close to the glass transition temperature of PCL. Further, it is shown by quantum chemical calculations that all the peaks obtained experimentally originate in skeletal vibrations of PCL. Therefore, it has become clear that a specific feature appears in the THz absorption spectrum of PCL associated with its glass transition.