No abstract

In the present study, we report the synthesis of a series of anthracene based polyfluorenes containing alkyl substituted 9,10-diphenylanthracene and hydrazone substituted fluorene moieties. The polymers were synthesized via copper catalysed Ullmann coupling, which comparatively is inexpensive as compared to palladium and platinum used in Suzuki coupling. The synthesized polymers were characterized by various spectroscopic techniques. All the polymers exhibited blue emission having band gap in the range of 2.7-2.83 eV. The polymers showed good thermal stability with decomposition temperature over 330 °C and glass transition temperature in the range of 125-140 °C. All the polymers were soluble in common organic solvents with weight average molecular weight in the range of 21,000-25,000. The electrochemical study reveals that the HOMO energy levels of the polymers were in the range of − 5.16 to − 5.26 eV which had elevated compared with that of polyfluorene (5.7 eV). It matched the work function of ITO and ITO/PEDOT: PSS (4.7 and 5.0 eV respectively). These results indicated that the synthesized polymers could be promising materials for applications in light emitting diode.

Five new alternating polymers were synthesized from 2,7‐dibromo‐3,6‐dimethoxy‐9‐sila fluorene with varied alkyl and aryl groups substituted at 9‐position and 2‐tert butyl‐9,10‐di (p hydroxyl phenyl) anthracene. The monomers and the polymers were synthesized in good yields at each stage of preparation and with high degree of reproducibility. The copolymers were soluble in common organic solvents like toluene, xylene, THF and chloroform. Chemical and optoelectronic characterizations of the polymers were done by 1H and 13C NMR, GPC, UV absorption, photoluminescence and cyclic voltammetric studies. Pure blue light emission, with the maximum absorption wavelength in the range of 445 to 457 nm and the PL quantum efficiency in the range of 0.55 to 0.91 were recorded for the synthesized copolymers in their solution in CHCl3. The ITO/CuPc/α‐NPD/ copolymer/ Alq3/LiF/Al devices fabricated from the polymers gave pure blue light emission irrespective of the substitution on silicon atom of the silafluorene moiety. The properties both photophysical and electrochemical, of the synthesized alternating polymers are quite suitable for the development of blue light emitting devices.

The light emitting polymers (LEPs) were synthesized by aromatic nucleophilic substitution reaction containing o-terphenyl substituted fluorene (TERF) and diphenylanthracene (DPA) units. The obtained polymers showed emission in the blue region. The polymers were successfully characterized by elemental analysis, FTIR and 1 H NMR spectroscopic studies.Polymers were thermally stable and soluble in various organic solvents. The electrochemical measurements and optical properties of the polymers were also studied. These light emitting materials showed high photoluminescence efficiency, making them good candidates as organic materials for light-emitting devices.[a] A.

A set of anthracene containing polyfluorenes (PFs) having 9,10-diphenylanthracene with alkyl substituents and aniline containing fluorenes were prepared. Commonly, light-emitting polymers were synthesized using expensive palladium-like catalysts. In the present work, palladium was replaced by copper as a cost-effective PF synthesis catalyst, which is also suitable for large-scale polymer synthesis. Synthesized PFs emit light in the blue region with a bandgap of 2.87–2.90 eV. Thermally stable PFs had a decomposition temperature of more than 305°C and a glass transition temperature of 125–138°C. PFs were soluble in organic solvents and had a molecular weight of around 21,700–25,500. The electrochemical study of these PFs showed low level of highest occupied molecular orbital (HOMO) energy of −5.16 to −5.26 eV, which was significantly higher than that of PF (5.7 eV). These findings suggested that the resulting PFs could be used as a component of the light-emitting diode.