Supramolecular polymerization through rotation of light-driven molecular motors

Molecular motors can act on their environment through their unique ability to generate non-reciprocal autonomous motions at the nanoscale. Although their operating principles are now understood, artificial molecular motors have yet to demonstrate their general capacity to confer novel properties on (supra)molecular systems and materials. Here we show that amphiphilic light-driven molecular motors can adsorb onto an air‒water interface and form Langmuir monolayers upon compression. By irradiation with ultraviolet light, the surface pressure isotherms of these films reveal a drastic shift toward a smaller molecular area as a consequence of motor activation. We explain this counterintuitive phenomenon by the rotation-induced supramolecular polymerization of amphiphilic motors through a non-thermal annealing process to escape a kinetically trapped amorphous state. The effect is limited by the maximum torque the molecular motor can deliver (~10 pN nm) and leads to the formation of highly organized patterns. This serendipitous discovery highlights the opportunities offered by molecular motors to control supramolecular polymerization for the design of innovative materials.