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[Display omitted] • The unique high-pressure infrared, dielectric, and volumetric data were analyzed. • T and p dependence of H-bonding energy along various isolines was studied. • A phase diagram of 2E1H, identifying isolines in the T - p plane, was constructed. • T controls the intramolecular dynamics of O H units in 2E1H. • The impact of density fluctuation grows with increasing T and weakening of HBs. The nature of H-bonding interactions is still far from being understood despite intense experimental and theoretical studies on this subject carried out by the leading research centers. In this paper, by a combination of unique high-pressure infrared, dielectric and volumetric data, the intramolecular dynamics of hydroxyl moieties (which provides direct information about H-bonds) was studied along various isolines, i.e., isotherms, isobars, isochrones, and isochores, in a simple monohydroxy alcohol (2-ethyl-1-hexanol). This allowed us to discover that the temperature controls the intermolecular hydrogen bonds, which then affect the intramolecular dynamics of O H units. Although the role of density fluctuations gets stronger as temperature rises. We also demonstrated a clear connection between the intra- and intermolecular dynamics of the associating liquid at high pressure. The data reported herein open a new perspective to explore this important aspect of the glass transition phenomenon and understand H-bonding interactions at varying thermodynamic conditions. [ABSTRACT FROM AUTHOR]

In this work, broadband dielectric spectroscopy (BDS) has been applied to investigate the aging kinetics in a low-molecular weight pharmaceutical - probucol (PRO) at various pressure (p) conditions. Unexpectedly, we found that isostructural relaxation times (τ i so , i.e., τ α in the glass), as well as the stretch exponent (β ag) calculated using the Casalini and Roland (CR) approach at 115 and 160 MPa, vary from the respective τ i so and β ag determined at 0.1 MPa. These results were different in regard to the data reported earlier for polymethylmethacrylate (PMMA). Further Fourier transform infrared (FTIR) measurements on the glass recovered from high- p experiments (pressure densified glass, PDG) allowed us to certify that most likely the change in the specific intermolecular interactions, namely the formation of weak, rarely observed O H⋯S hydrogen bonds might be responsible for that. Moreover, taking into account the values of β ag (free parameter) obtained from the analysis of aging data using the CR approach, we estimated primitive relaxation times (τ 0) from the Coupling Model, which were close to experimental Johari-Goldstein (JG) β -relaxation times (τ JG-β). Findings reported herein may contribute to a better understanding of the aging phenomenon occurring in the pressurized H-bonded systems. Unlabelled Image • τ i so calculated using the CR model at elevated p vary from those obtained at 0.1 MPa. • The observed behavior is different than that reported for polymethylmethacrylate. • Weak O H∙∙S hydrogen bonds are formed in probucol at high compression. • Our results enable a better understanding of the aging process in pressurized systems. [ABSTRACT FROM AUTHOR]