Swelling-state-dependent structure of spread microgel monolayers

• Neutron reflectometry elucidates the interfacial structure of thermo-responsive microgel monolayers with nanometer resolution. • The adsorption–collapse pathway governs corona conformation, particle protrusion, and lateral interactions at the interface. • Pathway-dependent interfacial reorganization provides a structural mechanism for tunable microgel-monolayer formation. Albeit largely studied, the interfacial restructuring that governs emulsion breakdown remains poorly understood. Here, we use neutron reflectometry to probe the structure of thermo-responsive microgel monolayers formed either above the volume phase transition temperature or collapsed in situ after adsorption. We find that the thermal history of the microgel critically affects the monolayer architecture, particularly the particle protrusion into the air phase. These insights reveal a pathway-dependent mechanism that governs microgel behavior at interfaces, underpinning the design of next-generation responsive emulsions and interfacial materials.