Crystallinity of poly(ethylene naphthalate) and its relation to terahertz absorption

Abstract

The crystallinity of poly(ethylene naphthalate) (PEN) was changed by thermal annealing and its effects on terahertz absorption spectra and X-ray diffraction patterns were examined. As a result, the intensity of a relatively sharp absorption peak at around 2.2 THz was found to be proportional to the crystallinity. As a plausible cause of this absorption, a lattice vibration, a torsional vibration, or their combination mode associated with (010) planes in crystal α of PEN is proposed. Therefore, the crystallinity of PEN can be estimated from the intensity of this absorption.

Evaluation of Crystallinity and Hydrogen Bond Formation in Stereocomplex Poly(lactic acid) Films by Terahertz Time-Domain Spectroscopy

“…Recently, it has been shown that terahertz spectroscopy can provide rich information regarding crystallization and hydrogen bond formation in polymeric materials. , Because various macromolecular vibration modes including the intramolecular vibration modes and the lattice vibration modes of crystalline states of polymers ,,− exist in the terahertz frequency range (0.1–10 THz or in terms of wavenumbers, 3.3–330 cm –1 ), the terahertz light can be used to directly probe the macromolecular vibration modes. For example, the determination of the crystallinity of materials like cellulose and poly­(vinyl chloride) has been achieved by the quantitative measurement of terahertz absorption caused by the lattice vibration modes. − Furthermore, the hydrogen bond formation in polymeric materials has been investigated by the comparison between terahertz and infrared spectra and quantum chemical calculations. ,, We note that spectroscopic studies of PLA in the terahertz regime have been performed to reveal the crystallization process ,,, and the strain-induced crystallization . Although there are several reports on terahertz spectroscopy of PLA, quantitative estimation of the crystallinity and detailed analysis of the hydrogen bond formation in sc-PLA, especially in the case of low crystallinity, are still lacking.…”

Terahertz spectroscopic estimation of crystallinity of poly(phenylene sulfide)

“…On this point, THz spectroscopy is useful for evaluating the crystallinity of polymers like PPS. The authors have already shown that THz absorption spectroscopy can be used to estimate the crystallinity of PEN . As we mentioned in Introduction and Experimental methods, in contrast to FTIR spectroscopy that is superior in ability to detect intramolecular vibrations, THz spectroscopy mainly detects intermolecular vibrations such as lattice vibrations.…”

“…Here, the crystallinity of a polymer is defined as the ratio of its crystalline parts to the whole volume or weight, depending on its measuring methods. The crystallinity is changeable in many polymers by various procedures such as mechanical stretching and thermal annealing . Therefore, in the present research, we changed the crystallinity of PPS by thermal annealing.…”

“…The crystallinity is changeable in many polymers by various procedures such as mechanical stretching and thermal annealing. 9,10 Therefore, in the present research, we changed the crystallinity of PPS by thermal annealing.…”

Study of Crystallinity and Conformation of Poly(lactic acid) by Terahertz Spectroscopy

“…In recent years, with the development of THz spectroscopy, its application in polymer materials has become increasingly widespread. Many studies have found that crystalline polymers have characteristic peaks in the THz band, whereas amorphous polymers have no peaks. , Considering that the lattice vibration of PLA is strong in the low-frequency region, most studies on PLA focused on its crystal structure. For example, Li et al.…”