INTERFERENCE OF MICROSTRUCTURE AND ISOTOPE LABELING EFFECTS IN POLYMER BLEND COMPATIBILITY

A model is developed which explains a recently-observed asymmetry in the phase-equilibrium behavior of mixtures of statistical ethylene (E)/ethylethylene (EE) copolymers E(xi)EE(1-xi), with differing microstructure and isotopic substitution levels. A coupling between the isotope and the microstructure contributions to the overall effective segmental interaction parameter chi is predicted, which could enhance or reduce chi depending on the ethylene content of the protonated component relative to that of the deuterated one. From the overall chi, the theory permits the extraction of the bare isotope interaction parameter chi(h/d) between hydrogenated and deuterated species and of the parameter chi(E/EE) for the E/EE interaction. This is done for the recent data set on coexistence in E/EE mixtures obtained by Eiser et al. The parameters thus estimated are compared with available experimental data on similar polyolefinic mixtures.