Elastocapillary Deformation of “Glassy”Polymer Micelles at an Air–Water Interface

We report direct in situ neutron reflectivity (NR) observations of elastocapillary deformation of nominally glassy polymer micelles at the air–water interface. Despite possessing glassy cores, adsorbed micelles undergo pronounced surface-tension-driven deformation, forming flattened structures. Core anisotropy changes sharply near the core glass-transition temperature (Tg), revealing a crossover from elastic elastocapillary deformation to relaxation-dominated surface micellization. Far below Tg, the deformation is fully reversible and yields an apparent Young’s modulus that depends strongly on nanoscale core thickness, highlighting surface-induced mechanical gradients within the core.