Light-Driven Surface Patterning of Supramolecular Polymers with Extremely Low Concentration of Photoactive Molecules

Light-induced surface patterning in azobenzene-containing polymers and other materials is a widely studied phenomenon with possible applications in fields ranging from photonics to biology. Yet, the fundamental understanding of this purely photodriven mass transport remains inadequate, and existing literature fails to define a threshold chromophore content for mass transport to occur, if such a limit exists. This letter presents a systematic study of the relationship between chromophore concentration and mass transport using hydrogen-bonded polymer-azobenzene complexes, in which the chromophore concentration can be freely adjusted while keeping the polymer backbone unchanged. Essentially, we demonstrate that effective surface patterning can be induced even at an extremely low chromophore content of 1 mol %, when only every tenth polymer chain carries a single azobenzene molecular motor. Importantly, the results highlight the extraordinary photomechanical power of azobenzene and contribute to the fundamental understanding of the light-induced motions.