Charge-Regulated Conformational Transitions Govern Nonmonotonic Pinch-Off Dynamics.

While molecular conformational changes significantly influence drop pinch-off, the governing mechanisms by which conformational evolution reshapes capillary-driven breakup remain elusive. Here, we isolate the role of conformation using charge regulation to drive conformational transitions in weak polyelectrolytes. We demonstrate that dissociation-driven chain expansion and counterion-mediated screening compete to generate nonmonotonic pinch-off dynamics. Furthermore, a slip-dominated intermediate thinning regime is identified, which is suppressed by concentration-dependent topological constraints. These results establish a physical picture in which conformation reorganizes pinch-off dynamics, while topological constraints select the route to breakup.