On the problem of direct observation of H-bridge interactions in polymers by FIR spectroscopy

Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics

“…Usually both forms are present in different degrees of disorder, as reported in [33,34]. The presence of the α-form in our PA6 sample is substantiated by the pronounced shoulder at 6.63 THz [33,34] previously attributed to a torsional vibration mode of the methylene chain [35]. At even higher frequencies one can identify the band centered at 13.4 THz (Fig.…”

“…These two peaks centered at 8.82 THz and 9.51 THz are fingerprints of the two different structures of PA6: respectively the α-PA6 with the CONH group coplanar to the methylene group planes and the γ-PA6 which has the CONH group perpendicular to those planes. Usually both forms are present in different degrees of disorder, as reported in [33,34]. The presence of the α-form in our PA6 sample is substantiated by the pronounced shoulder at 6.63 THz [33,34] previously attributed to a torsional vibration mode of the methylene chain [35].…”

“…In contrast to previous studies performed using FTIR [26][27][28][29][31][32][33][34][35], THz TDS provides a unique access to both the real and the imaginary part of the dielectric function. Besides, unlike FTIR, THz TDS is an ultrafast technique which can be easily used in pump-probe arrangement, thus directly yielding the dynamics of the ultra-broadband THz response of material of interest under ultrafast illumination.…”

Characterization of Micro-Powders for the Fabrication of Compression Molded THz Lenses

“…The highest absorbance by far is found for PA (#18), with values of the absorption coefficient α of 16 cm -1 at 1 THz and a strong increase with frequency. A similar behavior has been reported in literature for bulk PA6 [39] which is supposed to arise from the vibration of the amide groups involved in hydrogen bonding in the crystalline domains [48]. The data for the PA sample is plotted up to 1.75 THz only, where it is limited by the dynamic range of the measurement.…”

Terahertz Vibrations and Hydrogen-Bonded Networks in Crystals

“…The THz spectroscopy enables the characterization of solid-state materials through the excitation of soft intramolecular vibrational modes, as well as intermolecular modes and hydrogen-bonding networks inherent to the molecular assembly in the solid state [102,103]. The stretching vibration of the hydrogen bond in the THz region reflects the bonding itself [104][105][106][107]. The formation of a hydrogen bond affects the vibrational modes of the groups involved in several ways, and infrared (IR) spectroscopy is a standard method for investigating the hydrogen bond in the solid state [52].…”