Hyperbranched luminescent polyfluorenes containing aromatic triazole branching units

Abstract

Using a new aromatic 1,2,4‐triazole branching monomer (4.8–13.3 mol %), three hyperbranched polyfluorenes (P2–P4) were synthesized by the Suzuki coupling reaction to investigate the structural effect on optoelectronic properties. Poly(9,9‐dihexylfluorene) (P1) was also prepared for comparative investigation. Their weight‐average molecular weights and polydispersity indices are in the range of 1.16 × 104 to 5.9 × 104 and 1.49–2.25, respectively. Optical properties, both in solution and film state, were investigated using absorption and photoluminescence (PL) spectra. In film state, the absorption and PL spectra peaked at 377–392 and 424–425 nm, respectively, blue‐shift with increasing triazole concentration. Furthermore, a linear relationship between 1/λmax,abs and 1/(1 − ntriazole) is correlated (n: molar fraction), indicating a smooth decrease in conjugation length by incorporation of the branch unit. The P4 containing 13.3 mol % triazole reveals stable blue emission even at 150 °C (in air). The HOMO and LUMO levels of P2–P4, estimated from cyclic voltammograms, are −5.69, −5.73, −5.78 eV and −2.63, −2.64, −2.63 eV, respectively. The maximal brightness (current efficiency) of the electroluminescent devices (ITO/PEDOT:PSS/P2–P4/Ca/Al) improves from 828 cd/m2 (0.19 cd/A) to 2054 cd/m2 (0.46 cd/A) with increasing triazole concentration. The results suggest that incorporation of aromatic 1,2,4‐triazole branch units is an effective way to improve annealing stability and EL performance of polyfluorenes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4465–4476, 2007

Hyperbranched fluorene-alt-carbazole copolymers with spiro[3.3]heptane-2,6-dispirofluorene as the core and their application in white polymer light-emitting devices

“…6,7 Secondly, hyperbranched polymers with a three-dimensional structure can prevent the aggregation of polymer chains, making the material form amorphous lms with good quality, and increase the glass transition temperature (T g ) of the polymers. [14][15][16] However, white-light-emitting hyperbranched polymers have rarely been reported. [14][15][16] However, white-light-emitting hyperbranched polymers have rarely been reported.…”

Assessing the impact of comorbid illnesses on death within 10 years in prostate cancer treatment candidates

“…However, its electron‐transport capability is poor 27. To improve the electron transport properties of PFs, varying electron‐withdrawing segments such as oxadizole,28, 29 triazole,30 quinoxaline,31 pyridine,32 and dibenzo[a,c]phenazine27 have been introduced into the PFs backbone.…”

Hyperbranched polymer-cored star polyfluorenes as blue light-emitting materials

“…The optical, electrochemical and thermal properties of the hyperbranched polymer-cored star polymers were investigated. These polymers exhibited good thermal and color stability in solid state, and there was no significant blue-green emission after the polymers had been annealed in air for 2.5 h. Their three-dimensional hyperbranched structures could effectively reduce the aggregation of the peripheral rigid linear conjugated polyfluorene chains.hyperbranched polymer, light-emitting diodes (LED), polyfluorenes, star polymer, Suzuki polycondensationIn recent years, three-dimensional conjugated macromolecules such as dendrimers, hyperbranched and star polymers have been widely used as light-emitting materials [1][2][3][4][5][6][7][8][9][10] . The rigid three-dimensional structures show superiority to the corresponding linear structures as light-emitting materials, because they can effectively suppress the aggregation of conjugated polymer chains and reduce the self-quenching of their luminescence [11,12] .…”

“…In recent years, three-dimensional conjugated macromolecules such as dendrimers, hyperbranched and star polymers have been widely used as light-emitting materials [1][2][3][4][5][6][7][8][9][10] . The rigid three-dimensional structures show superiority to the corresponding linear structures as light-emitting materials, because they can effectively suppress the aggregation of conjugated polymer chains and reduce the self-quenching of their luminescence [11,12] .…”