Chiral Polyfluorene Derivatives:  Synthesis, Chiroptical Properties, and Investigation of the Structure−Property Relationships

Four polyfluorene derivatives with chiral center in the backbone or at the side chain, P L PheF ( P 1 ), P L PhGlyF ( P 2 ), P D PheF ( P 3 ), and PSPF ( P 4 ), have been designed and synthesized through the Pd-catalyzed Suzuki polymerization. The structures of these polymers are characterized by 1 H and 13 C NMR, UV−vis, photoluminescence (PL), and CD spectroscopic methods as well as elemental analysis. These four polymers exhibit the linearly polarized photoluminescence in dilute solutions. The investigation of the absorption and emission behaviors indicates that the aggregates and/or the excited states excimers might be formed in THF solution at higher concentrations. We also observe the emission dichroic ratio R PL of these polymers in films is increased in comparison with that in solutions. After film annealing, polymers P 1, P 2, and P 3 also show obvious linearly polarized photoluminescence at 500−650 nm. Moreover, the films of polymer P 4 exhibit good thermal spectral stability after annealing in comparison with other three polymers P 1, P 2, and P 3 . We also report the circular dichroism (CD) spectroscopic properties of these four polymers in THF solutions.