DIELECTRIC STUDY OF SUPERCOOLED TRIPHENYLPHOSPHITE AND BUTYRONITRILE - COMPARISON WITH A MESOSCOPIC MODEL

Dielectric relaxation has been studied in the supercooled liquids trip henylphosphite (TPP) and butyrontrile (BN). BN is relatively strong ac cording to Angell's classification and can be characterized by a fragi lity index m = 47. TPP, on the other hand, appears to be the most frag ile non-polymeric liquid studied so far (m = 160). The dielectric resp onse of the two glass-formers exhibits different degrees of non-expone ntiality which is analyzed in terms of a mesoscopic model of dynamical ly correlated domains. The relation of this model to the strong versus fragile liquid classification scheme is discussed.