Vogel-Fulcher-Tamman type

The Arrhenius plot of the viscosity of the ILs is not a straight line but a Vogel-Fulcher-Tamman (VFT) type curve. Since ionic conductivity is the inverse of the viscosity (Eq. (3.8)), it also obeys the VFT equation. 

Pentyl-4 -cyanobiphenyl and 4-octyl-4 -cyanobiphenyl liquid crystals (LCs) confined in molecular sieves of MCM-41 and cloverite types are studied in a wide temperature range by dielectric spectroscopy, thermal analysis and in-situ FTIR spectroscopy. The phase transitions of the bulk LCs cannot be detected when confined in MCM-41 sieve. A relaxational process occurs due to the molecular motions in the layer at the pore walls the temperature dependence of the characteristic frequency obeys a Vogel-Fulcher-Tamman law associated to a glassy state. In the cloverite cages, the LCs keep the phase transitions of the bulk but shifted. Interactions between Lewis and Brdnsted sites and the LC molecules are monitored by IR spectroscopy. DTA measurements put also in evidence strong guest-host interactions. 

The non-Arrhenius-type fluids widely exist. The typical cases include the Vogel-Fulcher-Tamman (VFT) type (Vogel 1921 Fulcher 1925 Tatnmann and Hesse 1926),... 

Glasses and polymer electrolytes are in a certain sense not solid electrolytes but neither are they considered as liquid ones. A glass can be regarded as a supercooled liquid and solvent-free polymer electrolytes are good conductors only above their glass transition temperature (7 ), where the structural disorder is dynamic as well as static. These materials appear macroscopically as solids because of their very high viscosity. A conductivity relation of the Vogel-Tamman-Fulcher (VTF) type is usually... 

Following the general trend of looldng for a molecular description of the properties of matter, self-diffusion in liquids has become a key quantity for interpretation and modeling of transport in liquids [5]. Self-diffusion coefficients can be combined with other data, such as viscosities, electrical conductivities, densities, etc., in order to evaluate and improve solvodynamic models such as the Stokes-Einstein type [6-9]. From temperature-dependent measurements, activation energies can be calculated by the Arrhenius or the Vogel-Tamman-Fulcher equation (VTF), in order to evaluate models that treat the diffusion process similarly to diffusion in the solid state with jump or hole models [1, 2, 7]. 

Type I. The conductivity of these compounds follows a free volume law in all experimental temperature ranges, reflected by a VTF (Vogel-Tamman-Fulcher) equation ... 

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