Abstract-Isothermal crystallization of poly(glycolic acid) studied by terahertz and infrared spectroscopy and SAXS/WAXD simultaneous measurements

Fumita Nishimura, Hiromichi Hoshina, Yukihiro Ozaki & Harumi Sato

https://www.nature.com/articles/s41428-018-0150-7

Isothermal crystallization of poly(glycolic acid) (PGA) has been studied using terahertz (THz) and infrared (IR) spectroscopy and simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements. Changes in the intermolecular interactions in PGA during the isothermal crystallization were monitored using THz spectroscopy, which is an efficient technique for analyzing the higher-order structure of polymers. In the THz spectra, the temporal difference in the intensity observed in the isothermal crystallization is due to the difference in the vibrational origins of two bands at 192 and 65 cm−1. The band at 192 cm−1 primarily originates from the intramolecular vibrational mode (twisting of the local structure of the PGA molecular chain). Furthermore, the band at 65 cm−1 exists due to the intermolecular vibration mode (C = O···H-C hydrogen bonds between polymer chains). In addition, these THz bands appeared after the appearance of the SAXS and WAXD peaks. When a lamellar structure is formed and the molecular chains are oriented, the THz band originating from the intermolecular vibration is observed. It is highly possible that the intermolecular vibration appearing in the THz spectra requires the molecular chains to be oriented.

Abstract-Three different kinds of weak C-H⋯O=C inter- and intramolecular interactions in poly(ε-caprolactone) studied by using terahertz spectroscopy, infrared spectroscopy and quantum chemical calculations

Chihiro Funaki, Shigeki Yamamoto, Hiromichi Hoshina, Yukihiro,Ozaki, Harumi Sato

https://www.sciencedirect.com/science/article/pii/S0032386118300260

The long range structure of poly(ε-caprolactone) (PCL) has been studied by terahertz (THz) spectroscopy, infrared (IR) spectroscopy and quantum chemical calculations (QCCs). Natural bond orbital (NBO) analysis and the calculation of the interatomic distances between C-H and O=C groups in PCL crystalline indicate that the PCL chain has three kinds of weak intermolecular interactions between the CH2 and C=O groups. In the IR spectra, significant changes due to the influence of hydrogen bondings were observed in the CH2 and C=O stretching vibration regions. The results of QCCs performed by using the Cartesian Coordinate Tensor Transfer (CCT) method to assign the THz spectra of PCL suggest that the peaks at 47 and 67 cm−1 reflect the atomic motions of the C=O + CH2 moiety derived from the weak C-H⋯O=C hydrogen bondings. THz spectroscopy allows us to observe the intermolecular hydrogen bondings of the polymer separately, since hydrogen bondings with different strengths yield different peaks in a THz spectrum. The results of THz and IR spectral analysis, and QCCs all indicate that PCL forms three kinds of weak intermolecular C-H⋯O=C hydrogen bondings between the CH2 and C=O groups. This may be one of the causes for the low melting temperature but high crystallinity of PCL. There are about six interactions in PCL and about sixteen interactions in polyglycolic acid (PGA), within the lamellar thickness. Therefore, it is suggested that the difference in the number of intermolecular interactions within the lamellar thickness leads to the difference in melting points between the two polymers.

Abstract-Terahertz Imaging of the Distribution of Crystallinity and Crystalline Orientation in a Poly(ɛ-caprolactone) Film

Chihiro Funaki, Takuya Toyouchi, Hiromichi Hoshina, Yukihiro Ozaki, Harumi Sato,

https://www.osapublishing.org/as/abstract.cfm?uri=as-71-7-1537&origin=search


The distribution of crystallinity and the crystalline orientation of a poly(ɛ-caprolactone) (PCL) film have been studied using terahertz (THz) imaging. Terahertz images were developed by using the intensity ratio of the two spectral peaks at 1.42 and 2.03 THz that are assigned to the crystalline modes parallel and perpendicular to the c-axis (I⊥/I||) of the PCL film. The obtained THz images show that the distribution of crystallinity and crystalline orientation vary considerably between the different regions in the PCL film, even though this inhomogeneity is not visible in the corresponding optical image. Our results clearly illustrate that THz imaging is a promising technique to characterize the physical properties of semi-crystalline polymers.

© 2017 The Author(s)

Abstract-Controlled Terahertz Birefringence in Stretched Poly(lactic acid) Films Investigated by Terahertz Time-Domain Spectroscopy and Wide-Angle X-ray Scattering

Hotsumi Iwasaki, Madoka Nakamura, Nozomu Komatsubara, Makoto Okano, Masayoshi Nakasako, Harumi Sato, and Shinichi Watanabe

J. Phys. Chem. B, Just Accepted Manuscript

DOI: 10.1021/acs.jpcb.7b04755

Publication Date (Web): June 16, 2017

Copyright © 2017 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acs.jpcb.7b04755?journalCode=jpcbfk


We report a correlation between the dielectric property and structure of stretched poly(lactic acid) (PLA) films, revealed by polarization-sensitive terahertz time-domain spectroscopy and two-dimensional (2D) wide-angle X-ray scattering (WAXS). The experiments evidence that the dielectric function of the PLA film becomes more anisotropic with increasing draw ratio (DR). This behavior is explained by a classical Lorentz oscillator model assuming polarization-dependent absorption. The birefringence can be systematically altered from 0 to 0.13 by controlling DR. The combination of terahertz spectroscopy and 2D WAXS measurement reveals a clear correlation between the birefringence in the terahertz frequency domain and the degree of orientation of the PLA molecular chains. These findings imply that the birefringence is a result of the orientation of the PLA chains with anisotropic macromolecular vibration modes. Because of a good controllability of the birefringence, polymer-based materials will provide an attractive materials system for phase retarders in the terahertz frequency range.