The dielectric relaxation behaviour of m-fluoroaniline above the glass transition

The dielectric properties of m-fluoroaniline have been investigated over seven decades of frequency (1 kHz-20 GHz) in the temperature range 188-303 K, above the calorimetric glass transition temperature. The Arrhenius plot of the inverse alpha peak frequencies reveals a non-linear character and a non-Debye relaxation function indicates a non-exponential temporal decay of the molecular polarization of the liquid near T g . The dynamic behaviour turns out to be typical of highly fragile liquids and appears closely similar to that obtained from previous ultrasonic studies on the same system. A crossover between two distinct dynamical regimes takes place in the range of intermediate viscosity at a temperature T c which falls about 40 K above the glass transition temperature T g .