Novel Blue Light Emitting Poly(N-arylcarbazol-2,7-ylene) Homopolymers: Syntheses and Properties

In this paper, we synthesized a new type of poly( N -phenyl-2,7-carbazole)s with alkoxy groups or a diphenylamino group at o -, m -, or p - position of the N -phenyl group using the Ni(0)-catalyzed Yamamoto polymerization in high yields. The series of structural isomers were synthesized in order to optimize the inter- and intramolecular interactions. The electron-rich triethylene oxide groups or the triphenylamino groups were introduced to tune the HOMO energy levels. These polymers were characterized by 1 H NMR, 13 C NMR, IR, elemental analysis, GPC, TGA, UV−vis, fluorescence spectroscopy, and electrochemical analysis. All the polymers had enough high molecular weights to show a good solubility in common organic solvents and a good processability for making thin films. Deiodination of the terminal residual iodide of the polymers enhanced the fluorescent quantum yields in CHCl 3 (φ f (sol) = 0.8). In the form of thin films, all the polymers displayed the fluorescence charts with emission bands around 430, 455, and 475 nm. Among the polymers, P m DPAC, P mp EHOC, P o DPAC, P op EHOC remarkably fluoresced blue (φ f (film) > 0.2). The strong fluorescence band around 430 nm for P mp EHOC and P o DPAC suggested a poor visibility, and 475 nm for P op EHOC resulted in an impure blue color emission, while the strong emission band around 455 nm for P m DPAC was appropriate for pure blue emission. Furthermore, the series of PDPAC polymers possessed higher HOMO energy levels than the other carbazole homopolymers.