Self-assembly of All-Conjugated Block Copolymer Nanoparticles with Tailoring Size and Fluorescence for Live Cell Imaging.

A series of all-conjugated polythiophene diblock copolymers containing hydrophobic (hexyl) and hydrophilic (triethylene glycol) side chains were synthesized via a nickel-catalyzed quasi-living polymerization. The correlations between block ratios and the self-assembled nanostructures of the block copolymers in thin films and in various solutions were examined. The copolymers dispersed in water via a slow dialysis method produced molecular-level self-assembled core-shell nanospheres with a crystallized hydrophobic core and a hydrophilic amorphous shell, which was proved by TEM images. The size and quantum yield of polymer micelles could be easily tuned via the block ratio of copolymers. The resulting core-shell nanospheres of BP40 composed of 40 mol% P3HT blocks with an average size of 120 nm exhibit high quantum yield (19% in aqueous medium), good photostability and low cytotoxicity. Utilized as a far-red/near-infrared (FR/NIR) cellular probe, BP40 is internalized efficiently by the cells and accumulated in the cytoplasm to give bright fluorescence.