Enthalpy recovery in polymeric glasses: Does a correlation exist between the empirical (T-N-M) relationship parameters and the glass structures?

To characterize the enthalpy recovery which appears during physical aging i n glassy materials and especially in glassy polymers, the empirical Tool-Na rayanaswamy-Moynihan (TNM) relationship for the relaxation time is widely u sed. This relationship depends essentially on three parameters, the apparen t activation energy Delta h*, the non linearity parameter x and the fictive temperature Tf. Even if a great amount of data (x, Delta h*) can:be found in the literature, no direct correlation between the values of these parame ters and the engaged structures are available. On the one hand, using some polymers like Poly(ethylene terephthalate), Polymethyl(alpha-n-alkyl)acryla tes and three dimensional epoxy networks for which structural changes are c ontrolled and on the other hand, using some recently published results conc erning other materials including inorganic polymers (Ge-Se and Ge-Te glasse s), we show that it is possible to propose some interesting tendencies. In particular it is shown that the value of x depends on the intermolecular st rength for organic polymers and on the connectivity for inorganic polymer.