A 2H NMR and dielelectric spectroscopy study of the slow β-process in organic glass formers
We study the slow β-process of several organic compounds by recording dielectric and 2H NMR spectra below the glass transition temperature Tg. For the neat systems toluene, polybutadiene, cis-decalin and ethanol as well as for the binary glasses chlorobenzene/cis-decalin and toluene/2-picoline, the β-process manifests itself in very similar changes of the 2H NMR spectrum when varying the spatial resolution by increasing the interpulse delay tp in the solid-echo pulse sequence. These findings indicate that for all considered glasses, in particular, for both components of the binary mixtures, molecular dynamics involved in the β-process are highly comparable. A line-shape analysis reveals that the secondary relaxation is mainly caused by a highly restricted, step-wise reorientation of essentially all molecules.For the neat glasses 2-picoline, glycerol and polystyrene (PS) which do not show a β-peak in dielectric spectroscopy, there is no evidence for molecular reorientation in the 2H NMR spectra at T < Tg. © 2002 Elsevier Science B.V. All rights reserved.
Publication Source (Journal or Book title)
Journal of Non-Crystalline Solids
Vogel, M., Tschirwitz, C., Schneider, G., Koplin, C., Medick, P., & Rössler, E. (2002). A 2H NMR and dielelectric spectroscopy study of the slow β-process in organic glass formers. Journal of Non-Crystalline Solids, 307-310, 326-335. https://doi.org/10.1016/S0022-3093(02)01492-8