The Miscibility of Hydrogen-Bonded Polymer Blends: Two Self-Associating Polymers

Abstract

The factors that determine the miscibility of two polymers, each of which hydrogen bonds (self-associates) to itself in the pure state, is discussed. Equations describing the contributions of hydrogen bonding to the free energy of mixing are presented. It is shown that mixtures of this type are much less likely to be miscible than those where only one of the components self-associates, while the other has hydrogen-bonding acceptor groups. In addition, for mixtures of two self-associating polymers, the volume fraction of the hydrogen-bonding functional group relative to the volume of the polymer repeat unit is an important factor in determining miscibility. If this quantity differs significantly in the two polymers being mixed, even if they have identical hydrogen-bonding functional groups, the mixture will phase separate.