Note on a potential contribution of entropy to the interaction parameter for dissimilar units in copolymers

The intrinsic viscosity data reported in the literature for ethylene-butylene copolymers in several solvents are used to estimate the x parameter characterizing the polymer-solvent interaction. The dependences of this parameter on the copolymer composition display unexpectedly pronounced minima which indicate a repulsive interaction of ethylene and butylene units. In view of their chemical similarity, which makes the enthalpy contribution to the interaction low, the behaviour is assigned to entropy-of-mixing effects.