Topology-based Transformation of Copolymer Phase Behavior and Immiscible Polymer Adhesion by Di-block Ring Polymers

The unique characteristics of nonconcatenated ring polymers, particularly their fractal globular conformations, and distinctive dynamics without persistent entanglement networks, offer transformative opportunities in block copolymer physics. Through large-scale molecular simulations of symmetric di-block ring polymers, we investigate both their phase behavior and interfacial adhesion properties. The absence of entanglement networks facilitates phase-separation kinetics, while the compact globular conformations necessitate higher enthalpic repulsion for lamellar phase separation compared to linear analogs. In the strong segregation regime, these polymers exhibit stretched conformations near lamellar interfaces while maintaining globular statistics at larger scales. The lamellar spacing demonstrates dependence on enthalpic repulsion and molecular weight, following a modified scaling relationship that accounts for the unique globular conformations. When applied as interfacial adhesives between immiscible polymers, di-block ring polymers demonstrate superior performance compared to their linear counterparts, with peak stress and failure strain approaching bulk values as ring length and surface coverage increase. The enhanced adhesion mechanism is attributed to the threading of di-block rings by linear chains from opposing interfaces, analogous to hook-and-loop fasteners. This threading, quantified through Gauss Linking Number analysis, creates stronger mechanical coupling across the interface than conventional chain entanglements. Our findings suggest that ring topology offers a powerful strategy for controlling phase behavior and enhancing interfacial strength, with implications for developing high-performance polymer materials with tunable morphologies and robust interfaces.