Direct Visualization of Segment-Like Dynamics in Isolated Polymer Chains on Solid Surfaces

The performance of polymer-based composites, coatings, and adhesives is critically governed by the dynamics of chains at solid interfaces, yet their molecular principles remain unresolved. Here, we use time-resolved atomic force microscopy to directly map segment-level relaxation dynamics in isolated polystyrene chains on atomically flat substrates. We uncover pronounced spatial heterogeneity, with some segments accelerating with temperature while others slowing down, a counterintuitive behavior arising from transient adsorption. These dynamics propagate into neighboring chains through interfacial coupling and extend the influence of adsorption beyond direct contacts. Molecular dynamics simulations corroborate the coexistence of thermally activated and adsorption-driven slowing processes, and experiments on catechol-functionalized chains demonstrate generality and relevance to adhesion on metal oxides. Our results establish a real-space framework for linking interfacial structure and chain dynamics. They also reveal isolated chains on solids as nonequilibrium systems, offering a paradigm for molecular-level design of adhesion and interfacial toughness.