Synthesis, Self-assembly, and Fluorescence Application of Bottlebrush Polyfluorene-g-Polycaprolactone with Conjugated Backbone and Crystalline Brushes

A series of bottlebrush copolymers with conjugated backbone and crystalline branch chains, polyfluorene-g-polycaprolactone (PF-g-PCL), are synthesized by combining Suzuki cross-coupling polymerization and cationic ring-opening polymerization. The PF-g-PCLs are prepared to self-assembled in solution and thin film. Due to the J-type aggregation of the polyfluorene main chains, the self-assembly spherical micelles have been observed. Meanwhile, in film, they exhibited self-assembly ringed spherulites because of the PF microregions in the bottlebrush copolymer. As a result of the interruption of PCL side chains, the aggregation tendency of PF main chains is weakened. And both the polymer solution and solid can overcome the aggregation-caused quenching to provide more pronounced fluorescence. Especially, owing to the good processability of the PF-g-PCL, as a fluorescent ink for different substrates, they can easily be prepared as high-brightness fluorescent films that are invisible under ambient light.