Liquid 1-propanol studied by neutron scattering, near-infrared, and dielectric spectroscopy

Abstract

Liquid monohydroxy alcohols exhibit unusual dynamics related to their hydrogen bonding induced structures. The connection between structure and dynamics is studied for liquid 1-propanol using quasi-elastic neutron scattering, combining time-of-flight and neutron spin-echo techniques, with a focus on the dynamics at length scales corresponding to the main peak and the pre-peak of the structure factor. At the main peak, the structural relaxation times are probed. These correspond well to mechanical relaxation times calculated from literature data. At the pre-peak, corresponding to length scales related to H-bonded structures, the relaxation times are almost an order of magnitude longer. According to previous work [C. Gainaru, R. Meier, S. Schildmann, C. Lederle, W. Hiller, E. Rössler, and R. Böhmer, Phys. Rev. Lett. 105, 258303 (2010)] this time scale difference is connected to the average size of H-bonded clusters. The relation between the relaxation times from neutron scattering and those determined from dielectric spectroscopy is discussed on the basis of broad-band permittivity data of 1-propanol. Moreover, in 1-propanol the dielectric relaxation strength as well as the near-infrared absorbance reveal anomalous behavior below ambient temperature. A corresponding feature could not be found in the polyalcohols propylene glycol and glycerol.

Communication: Supramolecular structures in monohydroxy alcohols: Insights from shear-mechanical studies of a systematic series of octanol structural isomers

“…This spectral feature is interpreted to originate from the same supramolecular structures responsible for the dielectric Debye process, and is identical to what is observed for short chain polymers. 21,22 Furthermore, it has been shown that also nuclear magnetic resonance, 17 dynamic light scattering, 3 and quasi-elastic neutron scattering 23 are sensitive to the Debye-process and similar results have been seen in mechanical studies of supramolecular polymers 1 and high temperature alcohols.…”

Nonlinear dielectric response of Debye, α , and β relaxation in 1-propanol

“…1 shows broadband loss spectra of 1-propanol obtained by conventional low-field dielectric spectroscopy, measured at various temperatures. As demonstrated in [26], where part of these data were already shown, these spectra can be reasonably fitted by the sum of three peak functions. For the curve at 112 K, these peak at the low well descr relaxation which a Co 1-propanol found in c was accou relaxation [20,21,31] the secon monohydro of dynamic are assume [32] but, microscopi dependent relaxation fits, are c discussed significant…”

“…It was shown [46], that the excess wing is caused by a secondary relaxation peak that is partly submerged under the dominating  peak. The  relaxation in 1-propanol can be assumed to be of Johari-Goldstein type [20,21,26,31]. The same was suggested for the secondary relaxation causing the excess wing in canonical dipolar glass formers like glycerol [46,47] (but also other opinions exist; see, e.g., [48]).…”

“…3(a) indicate the -relaxation rates   = 1/(2  ) as determined from fits of low-field permittivity spectra [26]. The onsets of the above-mentioned shoulders, observed at frequencies beyond the peak of  ln ε"(), obviously arise at frequencies close to   .…”

Investigation of nonlinear effects in glassy matter using dielectric methods

“…12(a)) and peak in " (Fig. 12(b)) while the  and  relaxations in this alcohol only show up as weak shoulders [127]. The insets of Fig.…”