Properties of Dilute Solutions of Ethylene-Propylene-Diene Terpolymers in Benzene and Toluene

Commercial samples of ethylene-propylene-diene terpolymers (EPDM) and their fractions were characterized by osmometry (number-average molecular weight, second virial coefficient), viscometry (intrisic viscosity) and 1 H NMR spectrometry (mole fraction of propylene monomeric units). The results were analyzed in terms of the two-parameter theory of polymer solutions. Theta temperatures and polymer-solvent interaction parameters were estimated and correlated with composition. Existence of organized structures is indicated by high values of the reduced partial molar entropy parameter y. The increase in y with increasing content of ethylene units is assigned to their association. The results lend support to the previous study on the Huggins viscosity coefficient of EPDM.