THERMODYNAMIC CHARACTERIZATION OF INTERPENETRATING POLYMER NETWORKS OF POLY(CARBONATE-URETHANE) AND POLY(METHYL METHACRYLATE)

Crosslinked poly(methyl methacrylate) and poly(carbonate-urethane) as well as full interpenetrating network on their base (IPN) were charact erized by precise heat capacity measurements in the temperature interv al 4.2-450 K. As judged by the positive sign of the excess Gibbs free energy in the whole temperature interval above 30 K, the apparently si ngle-phase state of IPN is thermodynamically unstable; however, its ki netic stability is ensured by permanent chamical crosslinks prohibitin g the incipient phase separation. (C) 1994 John Wiley & Sons, Inc.