Near infrared light regulated crystallization-driven self-assembly: a versatile platform for controlled preparation of uniform π-conjugated functional nanostructures.

Photo-controlled block copolymer self-assembly to modulate the morphology and dimensions of polymer nanoparticles (PNPs) has attracted growing interest. However, most photo-induced polymer self-assembly approaches are dependent on ultraviolet- or visible-light-based photochemical reactions that lead to structural variations of the PNPs. The limited morphology control of these approaches hinders their broad applications. Here we report a novel near-infrared (NIR) light regulated self-seeding strategy for the controlled preparation of uniform π-conjugated nanofibers of a 4-BBT-OPE3-P2VP22 block copolymer. This approach combines a NIR light induced photothermal effect with living crystallization-driven self-assembly (CDSA). By taking advantage of excellent photothermal activity and crystallinity of the 4-BBT-OPE3 segment, uniform helical fiber-like micelles could be generated with tunable lengths from ∼40 nm to 1.1 µm, photothermal activity and NIR-II emission. The lengths of these fiber-like micelles could be regulated by the time and power of NIR irradiation (808 nm laser). Moreover, the NIR light regulated self-seeding strategy could also be extended to core-crystalline block copolymers that lack a NIR-absorbing group if a NIR-absorbing dye like indocyanine green was added to the solution. Given the appealing merits and versatility of NIR light regulated self-seeding, this work paves a new way toward precise preparation of "smart" functional nanomaterials.