ENTHALPY RELAXATION IN VAPOR-DEPOSITED BUTYRONITRILE

Spontaneous enthalpy-evolution processes reported previously for vapor-deposited noncrystalline samples of solid butyronitrile were analyzed in terms of the equations of Kohlrausch, Williams and Watts (KWW), and of Adam and Gibbs (AG). The application of the KWW equation showed that the enthalpy relaxation deviated significantly from exponential behavior. The fractional exponent β characterizing the non-exponential nature was found to be 0.07 at 83.8 K, 0.11 at 89.7 K and 0.21 at 95.0 K. The significant deviation of β from unity reflects the extremely high fictive temperature of the specimen. The AG equation fitted the relaxation data well suggesting that the chemical potential Δμ hindering the cooperative rearrangement of molecules at each temperature was almost constant. The results were compared with other data derived from glasses prepared by conventional cooling of liquids. © 1990.