Disordered heteropolymers with cross-links – phase diagram and conformational transitions

The phase structure of globular random heteropolymers with quenched cross-links is studied by replica field theory. Our analysis predicts the occurrence of complex freezing patterns with few conformations sampled. The low cross-linking temperature phase is attributed to microphase separation of the pre-gel state with cross-links forming at the microphase interfaces. A first-order transition occurs at higher cross-linking temperatures by an increase of the microdomain size by statistical matching of microphases bounded by cross-links. At higher cross-linking temperatures, a second-order transition is predicted to a sequence-stabilized globular state.