INTERFERENCE OF MICROSTRUCTURE AND ISOTOPE LABELING EFFECTS IN POLYMER BLEND COMPATIBILITY

A model is developed which explains a recently-observed asymmetry in t he phase-equilibrium behavior of mixtures of statistical ethylene (E)/ ethylethylene (EE) copolymers E(xi)EE(1-xi), with differing microstruc ture and isotopic substitution levels. A coupling between the isotope and the microstructure contributions to the overall effective segmenta l interaction parameter chi is predicted, which could enhance or reduc e chi depending on the ethylene content of the protonated component re lative 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 s et on coexistence in E/EE mixtures obtained by Eiser et al. The parame ters thus estimated are compared with available experimental data on s imilar polyolefinic mixtures.