THERMODYNAMIC STUDY OF GLASS TRANSITIONS IN MISCIBLE POLYMER BLENDS

Contemporary theoretical considerations of glass transitions in miscib le binary polymer blends give the thermodynamic functions associated w ith the excess properties of mixing in liquid and glass states. A stri king feature of the present analysis is that fewer assumptions are inv olved in the derivations. The values of the new parameters are reporte d for a number of polymer pairs, representing various types of intermo lecular interactions. It is demonstrated that the enthalpy and entropy of mixing are virtually discontinuous at the glass transition tempera ture of the blend, T-gb, particularly for the cases of large deviation s of T-gb from the weight-average values. In addition, the difference between the polymer-polymer interaction parameters of the blend in the liquid and glassy states, Delta chi, is indeed linearly related to th e reciprocal of T-gb. Other implications of the results are discussed.