Thermodynamics Research Center / ThermoML | Thermochimica Acta

Johari-Goldstein relaxation in orientationally disordered phase of hexa-substituted benzenes

Singh, A. K.[Abhishek K.], Murthy, S. S. N.
Thermochim. Acta 2015, 604, 33-44
ABSTRACT
We have studied the orientationally disordered phase in solid solutions of two hexa-substituted benzenes, pentachlorophenol (PCP) (C6Cl5OH) and hexachlorobenzene (HCB) (C6Cl6) at five concentrations encompassing the entire concentration range employing dielectric spectroscopy and differential scanning calorimetry. In the observed dielectric relaxation spectra, the primary or a-process is accompanied by an additional process on the high frequency side which gets resolved increasingly with increase in the concentration of non-polar HCB. The physical parameters of PCP HCB solid solution are found to vary according to Gordon Taylor equation. The resolved second process lies in close proximity to the b-process predicted using Coupling Model proposed by Ngai (1998, 2011). We obtained similar results in neat pentachloronitrobenzene (C6Cl5NO2) and pentabromotoluene (C6Br5CH3). In all the samples studied, the a-process is found to be more or less Arrhenius in its temperature dependence.
Compounds
# Formula Name
1 C6HCl5O pentachlorophenol
2 C6Cl6 hexachlorobenzene
Datasets
The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type Compound-# Property Variable Constraint Phase Method #Points
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1
  • Crystal 1
  • Liquid
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal 3
  • Crystal 3
  • Crystal 2
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 3
  • Crystal 3
  • Crystal 2
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 4
  • Crystal 4
  • Crystal 3
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Normal melting temperature, K ; Crystal 1
  • Crystal 1
  • Liquid
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 2
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal
  • Crystal
  • Liquid
  • Air at 1 atmosphere
  • DSC
  • 1
  • POMD
  • 2
  • Normal melting temperature, K ; Crystal 1
  • Crystal 1
  • Liquid
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • 2
  • Solid-liquid equilibrium temperature, K ; Liquid
  • Mole fraction - 2; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Crystal 1
  • DTA
  • 7