Photocrosslinkable hyperbranched polyfluorenes containing oxadiazole: synthesis, photophysics and electroluminescence

Abstract

BACKGROUND: Crosslinkable hyperbranched polymers have great potential for use in organic light‐emitting devices and photovoltaics. With this in mind, two crosslinkable hyperbranched polyfluorenes, P5 and P6, containing oxadiazole as the core, and linear polyfluorene P0 were synthesized via palladium‐catalyzed Suzuki coupling. A device was also made. RESULTS: The resulting polymers were characterized using NMR, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. The spectral behavior of the polymers was also investigated. Compared with uncrosslinked P5 and P6, the photoluminescence spectra of crosslinked P5 and P6 were little influenced by the crosslinking. After annealing for 3 h at 200 °C in air, the photoluminescence of P6 (with a greater content of branched units) showed excellent stability compared with that of P5 and P0. The results for the device revealed that photocrosslinking improves the stability of the electroluminescence. CONCLUSION: The crosslinkable polymers obtained can be used in multilayer devices. Copyright © 2008 Society of Chemical Industry

Structure–Property Relationships of Solution‐Processable Diarylethene‐Based Main‐Chain Photochromic Polymers

“…[58,59] The transitions are weak and are similar to those of polyfluorenes. [60] The T g of P4, P5, and P6 vary from 49 to 96 °C and show little dependence on conjugation length (Figure S7, Supporting Information).…”

Polyfluorenes

“…Photo-cross-linkable groups were introduced into the side chains at C-9 positions of fluorene, and then hyperbranched PFs of P58 and P59 (Scheme 9.31) were synthesized by the Suzuki coupling reaction [103,104]. The polymers with higher content of the core exhibit more stable PL spectra even after annealing at high temperature.…”

Polyfluorene‐Based Blue‐Emitting Materials

“…In order to utilize this technique, we introduced photocrosslinkable groups into the side chains at C-9 positions of fluorenes and synthesized blue-emitting hyperbranched PFs P10 and P11. [35,36] These polymers can be crosslinked photochemically by the crosslinkable group and the photocrosslink has little influence on the PL spectra of the polymers. These hyperbranched crosslinkable PFs possess no distinct T g before 200 8C and exhibit good thermal stability with T d higher than 350 8C.…”

“…Initiated with ultraviolet light, heat, electron beams, etc., soluble polymers can be crosslinked into insoluble network structures. In order to utilize this technique, we introduced photocrosslinkable groups into the side chains at C‐9 positions of fluorenes and synthesized blue‐emitting hyperbranched PFs P10 and P11 35, 36. These polymers can be crosslinked photochemically by the crosslinkable group and the photocrosslink has little influence on the PL spectra of the polymers.…”