Long-Range Order Self-Assembly of Conjugated Block Copolymers at Inclined Air-Liquid Interfaces

Here, we report that long-range order, direction-controlled, ultrathin conjugated polymer films can be formed by the self-assembly of conjugated block copolymers (i.e., poly(3-hexylthiophene)-block-poly(ethylene glycol)) at inclined air-water interfaces. Structure analyses revealed well-aligned nanowire arrays of poly(3-hexylthiophene) with a dramatically increased ordered domain size compared to the polymer films formed on a flat water surface. The improved degree of order was attributed to the flow field created by the enhanced solvent evaporation at the top of the water contact line. Note that it is challenging to prepare such well-ordered and molecularly thin films of conjugated polymers by conventional fabrication methods. The long-range order polymer film showed hole mobility an order of magnitude higher than polymer films formed on a flat interface when implemented as an active layer of field-effect transistor devices. This study demonstrates that a simple interface modification can significantly impact the self-assembly process, structure, and function of polymer films formed at the air-liquid interface.