Hierarchical Self-Assembly of Amphiphilic Semiconducting Polymers into Isolated, Bundled, and Branched Nanofibers

Herein, we report a high-yield click synthesis and self-assembly of conjugated amphiphilic block copolymers of polythiophene (PHI) and polyethylene glycol (PEG) and their super-structures. A series of different length PHTm-b-PEG(n) with well-defined relative block lengths was synthesized by a click-coupling reaction and self-assembled into uniform and stably suspended nanofibers in selective solvents. The length of nanofibers was controllable by varying the relative block lengths while keeping other dimensions and optical properties unaffected for a broad range of f(PHT) (0.41 to 0.82), which indicates that the packing of PHI dominates the serf-assembly of PHTm-b-PEG(n). Furthermore, superstructures of bundled and branched nanofibers were fabricated through the self-assembly of PHTm-b-PEG(n) and preformed PHI nanofibers. The shape, length, and density of the hierarchical assembly structures can be controlled by varying the solvent quality, polymer lengths, and block copolymer/homopolymer ratio. This work demonstrates that complex superstructures of organic semiconductors can be fabricated through the bottom-up approach using preformed nanofibers as building blocks.