Interface-Directed Self-Assembly of Thermoresponsive Block Copolymers for Tunable Interfacial Nanostructures

Interfacial nanopatterning is central to nanotechnology, with applications ranging from electronics to sensing and soft nanofabrication. Conventional approaches often rely on top-down methodologies that require high energy inputs and sophisticated equipment, and offer limited scalability. Bottom-up strategies, particularly block copolymer (BCP) self-assembly, have emerged as attractive alternatives, yet they generally yield static structures whose dimensions are dictated by BCP macromolecular parameters. In this work, we introduce an additional level of tunability by exploiting the thermoresponsiveness of one block within an amphiphilic BCP. Poly(N-isopropylacrylamide)-block-(2-acetoacetoxyethyl methacrylate), P(NIPAM-b-AEMA), was synthesized and self-assembled at the air-water interface using a Langmuir-Pockels trough. Surface compression and temperature guide the evolution of the monolayer from continuous films to spherical nanodomains. Atomic force microscopy (AFM) and grazing-incidence small-angle x-ray scattering (GISAXS) show that compression mainly controls the spacing between nanodomains, whereas temperature changes their size, spacing, and order through thermoresponsive reorganization of the interfacial film. Above the P(NIPAM) lower critical solution temperature, the nanodomain array becomes more regular, consistent with temperature-induced reorganization of the copolymer at the interface. These results identify thermoresponsive BCPs as useful platforms for tunable interfacial self-assembly and provide a simple route to stimuli-responsive nanostructures at fluid interfaces.