Abstract
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.
Highlights
Broadband dielectric spectroscopy (BDS) extensive studies of 4M2P have been conducted at ambient and elevated pressure
The Broadband dielectric spectroscopy (BDS) system equipped with the Alpha impedance analyzer and Quatro Cryosystem by Novocontrol GmBH have been employed in the frequency range from 10μHz up to 3 MHz at temperatures from 150 K up to 323 K
To other monohydroxy alcohols with hydroxyl group located at the terminal position of the carbon chain, we have observed the so-called Debye-like relaxation at elevated pressure in case of 4M2P, which has been measured along 16 isotherms and 1 atmospheric isobar
Summary
Broadband dielectric spectroscopy (BDS) extensive studies of 4M2P have been conducted at ambient and elevated pressure. High pressure isothermal dielectric measurements have been performed in the pressure range from 0.1 MPa up to 1.8 GPa (varying depending on isotherms) and in the temperature range from 203 K up o 323 K, using two pressure systems described elsewhere[27]. 32,33), we have observed the so-called Debye-like relaxation at elevated pressure (or the Debye process at ambient pressure) in case of 4M2P (see Supplementary Fig. S1), which has been measured along 16 isotherms and 1 atmospheric isobar.
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