Decreased aggregation phenomena in polyfluorenes by introducing carbazole copolymer units

To decrease aggregation phenomena and improve the luminescence of the blue-light-emitting polymer polyfluorene, carbazole units were copolymerized to introduce disorder in the polymer backbone. A "kink" linkage was introduced into the polyfluorene chain by forming a 9:1 and 7:3 copolymer with the carbazole group at the 3,6 positions. The disordered polyfluorene was made though a Ni-catalyzed reaction, which resulted in high yield and high molecular weight polymers. The structure and physical properties were confirmed by NMR, SEC, UV absorption, photoluminescence, elemental analysis, and quantum yield measurements. The copolymers exhibited better spectral properties both in solution and in film compared to previously synthesized polyfluorene homopolymers. Annealing studies showed both improved thermal and UV stability of the copolymer over previously reported homopolymers. Cyclic voltammetry studies showed a slightly lower highest occupied molecular orbital (HOMO) than the homopolymer.