Polymer blending is an important route to obtaining new polymer materials that are easier to process and have tunable properties. We are studying a new class of polymer blends: traditional linear polymers blended with end-to-end associating supramolecular polymers. These hybrid systems are expected to exhibit unusual phase behavior since the size of the supramolecular component (virtual molecular weight) depends on temperature. A simple model is used to predict how the phase behavior of idealized polymer - (supramolecular polymer) binary blends differs from that of traditional polymer-polymer blends. Inputs to the model include the lengths of the unimers and polymers, the free energy of forming supramolecular bonds, and a Flory-Huggins interaction parameter. The model calculates the equilibrium degree of association for a pure supramolecular polymer and that of a mixture containing a supramolecular component and a monodisperse polymer. The free energy of mixing is calculated to determine whether the components are miscible. This exercise is repeated as a function of composition and temperature to construct phase diagrams. Resulting diagrams exhibit an upper critical solution temperature, though phase boundaries are asymmetric and the critical point is at a different location when compared to classical polymer-polymer blends. The results from our model have seeded an effort to experimentally verify predictions.
