Thermodynamics of Associative Polymer Blends

We report on a theoretical study of the phase behavior of polymer blends with hydrogen-bonding (HB) groups using the mean-field approximation. The hydrogen bonds are modeled as saturable bonds. We find the parametric conditions for lower and upper critical solution temperatures (LCST and UCST) and the eutectic behavior for the HB polymer blends. We quantify the conditions for the miscibility, partial miscibility, and immiscibility of HB polymer blends. We evaluate the conditions for the applicability of the Flory–Huggins theory to HB polymers by analyzing the composition dependence of the effective Flory–Huggins interaction parameter χeff. We use the polymer self-consistent field theory together with our model to compute the interfacial tension between coexisting phases in HB blends and find that intercomponent hydrogen bonding may significantly reduce the interfacial tension relative to a regular polymer blend at the same degree of segregation.