Enhancement of color purity in blue light emitting poly(fluorene)s and poly(p-phenylene)s with 2,6-distyrylpyridine kinked segments along the backbone

摘要

2,6-bis(4-Distyrylpyridine) (1) was synthesized by the condensation of 2,6-dimethylpyridine with 4-bromobenzaldehyde. Two new series of soluble random or alternating polyfluorenes (PF-Py) and poly-p-phenylenes (PP-Py) with various compositions were prepared by Suzuki coupling utilizing 1 as a comonomer. These polymers showed optical band gaps of 3.00-3.07 eV and photoluminescence (PL) quantum yields in solution of 0.37-0.91 for PF-Py and 0.29-0.38 for PP-Py. Polymers PF-Py emitted blue light with PL maximum at 410-424 nm in solution and 406-428 nm in thin films that was red shifted with increasing distyrylpyridine content. Polymers PP-Py behaved as blue emitters both in solution and in solid state, with PL maximum at 416-436 nm. The optical properties of these polymers could be tuned by the reversible protonation-deprotonation process of the pyridine ring. The emitted color of the polymers in solution and thin film could be changed continuously between blue and green (PL maximum up to about 520 nm) by exposing the polymers to the acid or base environment. Thin films of PF-Py displayed excellent color stability with a small red shift of 10 nm but without additional emission band in the long wave region of the spectrum, even after being annealed at high temperature for a long time. (c) 2005 Wiley Periodicals, Inc.