Hyperbranched Blue-Light-Emitting Alternating Copolymers of Tetrabromoarylmethane/Silane and 9,9-Dihexylfluorene-2,7-diboronic Acid

Abstract

The first soluble hyperbranched tetrahedral polymers were prepared by Suzuki coupling polycondensation reaction between tetrabromoarylmethane/silane and 9,9-dihexylfluorene-2,7-diboronic acid at low concentrations. The polymers exhibited high thermal stability with their decomposition temperatures (T ds) in the range 352−449 °C. The polymers emitted blue light highly efficiently in both solution and the solid state. The photoluminescence quantum efficiencies of the polymers in THF solution were in the range 73−99%, and those in thin films were 38−82%. The film PL spectra of the polymers exhibited similar spectral patterns to those determined in solutions, with 1−8 nm red shift in their emission maxima and 0−8 nm increase in their full width at half-maximum (fwhm) values being observed. No long wavelength excimer-like emissions at 500−600 nm, which were typical for polyfluorenes due to their self-aggregation in the solid state, were observed. Thus, the polymers were less prone to self-aggregation in the solid state due to their hyperbranched structures. A double-layer polymer light-emitting diode (PLED) device with a configuration of ITO/PEDOT/polymer/LiF/Ca/Ag was fabricated. The device showed bright blue emission peaking at 415 nm with an external quantum efficiency of 0.6% and a turn voltage at 6.0 V. The synthetic simplicity, good solubility and solution processability, high PL quantum efficiencies in solution and the solid state, and nonaggregating property in the solid state would make the present polymers a novel class of blue emitters.

Synthesis and X-ray Crystal Structures of New Tetrahedral Arylethynyl Substituted Silanes

“…To conclude, from the results it is demonstrated that the given molecular constructions are distinguished by a high degree of tetrahedral shape persistency, providing impact as structurally controlled subunits for the future design of supramolecular building blocks such as precursors of dendrimers [41], polymers [20,42], liquid crystals [43] or materials with other applications [21].…”

Excimer and electromer suppression of tetraphenylsilane‐based blue‐light‐emitting polymers

“…[13][14][15][16] Recently, a series of tetraphenylsilane-based hyperbranched blue-light-emitting alkylfluorene copolymers were developed by He and coworkers. [17][18][19] No excimer formation in longer wavelength like emissions at 500-600 nm was observed for such hyperbranched PFs. The color purity of blue emissions was shown to be improved by the reduction of the aggregates formed by polymer-chain p-p stacking in the solid state of PFs.…”

“…However, the presence of the tetrahedral molecular skeleton of tetraphenylsilane groups or the hyperbranched structure effect on the reduced aggregation and excimer formation of PF were not clarified. [17][18][19] More recently, a comparative study on light-emitting copolymers of fluorene and carbazole with a full conjugated or Si-interrupted structure was carried out by He et al 20 The results seem to conclude that the self-aggregation of PF could be significantly reduced because of the steric effect of the tetrahedral molecular skeleton of teterphenylsilane groups. In fact, the maximum and full width at half-maximum (fwhm) of the emissions were not reduced as the conjugated structure was interrupted by the teterphenylsilane group.…”

Fabrication of graphene oxide and hyperbranched polyurethane composite via in situ polymerization with improved mechanical and dielectric properties

“…Hyperbranched polymers (HPs) are highly branched polymers prepared from multi‐functional monomers. In addition to their easy synthesis , their three‐dimensional dendritic structure confers them with many advantageous properties over traditional linear polymers such as their non‐aggregation, high solubility , and low viscosity. Considerable research attention has been devoted to hyperbranched polymers in recent years owing to their interesting properties, which makes them potential candidates for applications ranging from coatings , non‐linear optical materials , light‐emitting diodes and sensors to catalysis .…”