Activation law parameters of viscoelastic subglass Relaxations from dynamic-mechanical moduli measurements as a function of temperature

The phenomenology of the subglass relaxation processes as a function of temperature is investigated, taking as a probe system the β relaxation behavior of a main chain segmented liquid crystalline polyester. Real (E′) and imaginary parts (E″) of the modulus were measured as a function of temperature in isochronal scans performed at different frequencies. The Cole arcs obtained plotting E″-(T) vs E′(T) revealed a non-Debye behavior of the β process, which is described by a Cole-Cole distribution of relaxation times. A procedure was outlined to determine accurate and reproducible values of the activation parameters by means of the E′(T) curves. The reliability of this procedure and of the data thereof was substantiated by the derivation of the activation law and its parameters by means of the reduced variables approach.