Inflection point in the Debye relaxation time of 2-butyl-1-octanol.

We report a striking anomaly in the pressure dependent Debye-relaxation time of the branched monohydroxy alcohol 2-butyl-1-octanol. Evidence of a crossover from slower to faster than exponential pressure dependency was obtained at different temperatures via high pressure broadband dielectric spectroscopy. At the same time, viscosity measurements reveal similar behavior in the viscosity, respectively, the structural relaxation time, indicating a similar origin of the phenomena.

Density Scaling Based Detection of Thermodynamic Regions of Complex Intermolecular Interactions Characterizing Supramolecular Structures.

In this paper, applying the density scaling idea to an associated liquid 4-methyl-2-pentanol used as an example, we identify different pressure-volume-temperature ranges within which molecular dynamics is dominated by either complex H-bonded networks most probably leading to supramolecular structures or non-specific intermolecular interactions like van der Waals forces. In this way, we show that the density scaling law for molecular dynamics near the glass transition provides a sensitive tool to detect thermodynamic regions characterized by intermolecular interactions of different type and complexity for a given material in the wide pressure-volume-temperature domain even if its typical form with constant scaling exponent is not obeyed. Moreover, we quantify the observed decoupling between dielectric and mechanical relaxations of the material in the density scaling regime. The suggested methods of analyses and their interpretations open new prospects for formulating models based on proper effective intermolecular potentials describing physicochemical phenomena near the glass transition.