Energy transfer through heterogeneous dyes-substituted fluorene-containing alternating copolymers and their dual-emission properties in the films

We report synthesis of the modified fluorene polymers tethered to the heterogeneous types of the fluorescent dyes at the cardo carbon for obtaining the dual-emissive solid materials. A series of the alternating fluorene copolymers modified with pyrene or 9,10-diphenylanthracene and BODIPY at the cardo carbon based on the red-emissive donor-acceptor structure were prepared, and their characteristics were examined. From the measurements of the optical properties, the energy transfer efficiencies were evaluated. In summary, variable energy transfer efficiencies were observed between the side chains and from the side chain to the main chain. It was indicated that the energy transfer efficiencies were strongly depended on the types of the energy donor and the detection conditions as such in the solution or film. Furthermore, it was found that the cardo fluorene units can contribute to the suppression of the energy transfer in the condensed state. Finally, the dual-emissive polymers were obtained in the film states. This is the first example, to the best of our knowledge, not only to offer systematic information on the energy transfer between the dye molecules and the polymer main-chains via the cardo structure but also to demonstrate the polymer-based optical materials with the dual-emission properties.