Blue light‐emitting hyperbranched polymers using fluorene‐co‐dibenzothiophene‐S,S‐dioxide as branches

A series of blue light‐emitting hyperbranched polymers comprising poly(fluorene‐co‐dibenzothiophene‐S,S‐dioxide) as the branch and benzene, triphenylamine, or triphenyltriazine as the core were synthesized by an “A₂ + A₂' + B₃” approach of Suzuki polymerization, respectively. All resulted copolymers exhibited quite comparable thermal properties with the glass transition temperatures in the range of 59–68 °C and relatively high decomposition temperatures over 420 °C. Photoluminescent spectra exhibited slight variation with the molar ratio of the dibenzothiophene‐S,S‐dioxide unit and the size of the core units. Polymer light‐emitting devices demonstrated blue emission with excellent stability of electroluminescence. Copolymers based on smaller core units of benzene and triphenylamine exhibited enhanced device performances regarding to that of triphenyltriazine. With the device configuration of ITO/PEDOT:PSS/polymer/CsF/Al, a maximum luminous efficiency of 4.5 cd A^?1 was obtained with Commission Internationale de L'.Eclairage (CIE) coordinates of (0.16, 0.19) for the copolymer PFSO15B. These results indicated that hyperbranched structure can be a promising strategy to attain spectrally stable blue‐light‐emitting polymers with high efficiency. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1043–1051