Isochronal superpositioning in the equilibrium regime of superpressed propylene carbonate to ∼ 1.8 GPa: A study by diffusivity measurement of the fluorescent probe Coumarin 1

Ion Dynamics in a Highly Compressed Solution of Tetra-Ethylammonium – Tetrafluoroborate Salt in Propylene Carbonate: A Study in the Equilibrium and Glassy States

“…The value P G = 2.30 GPa for the isotherm at T = 295.35 K is close to the glass transition pressure P G = 2.12 GPa calculated from the dielectric measurements of Kondrin et al 53 in pure PC at T = 292.3 K, corresponding to the isochronal line   150 s. The current glasstransition pressure is also very close to P G 2.29 GPa measured in a solution of 10 -3 M Coumarin 1 in PC at 296 K using the ruby fluorescence method. 59 This shows that the weak ion concentration in the solution does not modifywithin the ± 50 MPa pressure accuracythe glass transition pressure.…”

“…60,61 The large diamond anvil culets used in our setup give a limiting pressure of 6 GPa at room temperature. 58,59 This limiting pressure is well above the glass transition pressure of propylene carbonate.…”

“…The glass transition pressure P G of the 10 -2 M solution is determined from the method based on the enlargement of the width  (nm) at half-maximum (FWHM) of the peak R 1 from the fluorescent emission of the ruby crystal embedded in the sample under pressure. 59,65 When the sample under uniaxial compression approaches the glass transition, stress gradients settle in the sample due to the high value of the sample viscosity. 65 These non-hydrostatic stresses lead to a broadening of the peak R 1 at wavelength  1 .…”

“…5,8,10,41,56,57 We show that the anomalous increase in dc-conductivity occurs at approximately the same crossover pressure P cross at which a dynamic change in the diffusivity of uncharged fluorescent molecules in propylene carbonate is observed. Indeed, for P  P cross , from the time-recovery of the fluorescent intensity in photobleaching experiments, 58,59 the molecular diffusivity has been shown to exhibit a more Arrhenius-like behavior for increasing pressure. This dynamic change could be related to the anomalous behavior of the ion transport observed between P cross and P G .…”

Phenol, the simplest aromatic monohydroxy alcohol, displays a faint Debye-like process when mixed with a nonassociating liquid

“…56 Furthermore, PC was studied by numerous other techniques as well. [57][58][59][60] PhOH, a very weak acid, and PC, a very weak base, 61 are not expected to react with each other. 62 A potential drawback of choosing PC as a mixing partner may be its large dipole moment of about 5 D, [63][64][65] while for PhOH some solution studies indicate an ''infinite dilution'' value of ''only'' 1.5 D. The sizeable dependence of PhOH's dipole moment on concentration and solvent could be taken as a hint for self-association effects.…”