Universal Scaling Behaviors of Interfacial Thickness in Polymer Globules

By employing parallel tempering molecular dynamics simulations with a bead-spring model, we investigate the universal scaling of interfacial thickness in polymer globules. Our findings reveal that while conventional predictions assuming a sharp interface effectively describe the transition in polymer size from coiled to globule states with temperature variations, they fail to capture the core density of the globules. This failure is attributed to a substantial interfacial thickness relative to the globule size, suggesting the existence of polymers in an intermediate regime before reaching fully collapsed states. Notably, the observed interfacial thickness displays universal scaling behaviors predicted by previous field-theoretical approaches, affirming the existence of a distinct intermediate globular regime identifiable by its unique scaling of interfacial thickness. We demonstrate that discrepancies in the scaling behavior of core density in intermediate regimes can be quantitatively accounted for by the universal scaling of interfacial thickness, highlighting the critical importance of considering interfacial thickness for a precise understanding of the conformations and associated structural properties of polymer globules.