FRACTON-LIKE HEAT-CAPACITY BEHAVIOR OF HETEROCYCLIC POLYMER NETWORKS AT LOW-TEMPERATURES

A unique feature of disordered (glassy) solids is the ''non-classical' ' behavior of their thermal properties at low temperatures. A typical example is the low temperature heat capacity (LTHC) of a glass C(g) wh ich exceeds in magnitude that of a corresponding crystal C(c) below a characteristic temperature T(a) congruent-to 1-2 K; moreover, in the i nterval of moderately low temperatures, T(a) < T < T(b) congruent-to 5 0-100 K, the exponent d in the scaling relationship C(g) approximately T(d) is both non-integer and smaller in magnitude compared to a class ical Debye value of 3 [1, 2]. These experimental observations reflect the intrinsic structural randomness frozen-in in glasses; in fact, the former observation may be traced back to the enhanced thermal mobilit y of small-size units in the loosely-packed regions of the glassy quas i-lattice [3, 4], whereas the latter one may be regarded as a manifest ation of a ''fracton-like'' vibration regime (i.e., localized vibratio ns on fractals) [5, 6].