Synthesis, light-emitting and optical limiting properties of new donor-acceptor conjugated polymers derived from 3,5-dicyano-2,4,6-tristyrylpyridine

Three donor-acceptor conjugated polymers P1-P3 derived from 3,5-dicyano-2,4,6-tristyrylpyridine (PY) have been synthesized through the Knoevenagel reaction. The polymers are characterized by 1H NMR, FTIR, UV-vis and elemental analysis. P1 and P2 have high molecular weight up to 2.3 × 105 and 29.5 × 105 and show excellent solubility in common solvents such as THF, CH2Cl2, CHCl3 and DMF. They all have relatively good thermal stability with the 5% weight loss temperature at 402, 264 and 364 °C in argon, respectively. The fluorescence spectrum of P1 displayed the maximum at 588 nm in chloroform solution and at 596 nm in thin film. Two bilayer light-emitting diodes, with 5% or 10% of P1 fabricated in poly (N-vinylcarbazole) (PVK), emitted light at 549 or 552 nm, respectively, and with the increasing content of P1, the electroluminescence efficiencies of the blend devices increased. The optical limiting performance of P1 had been measured at 532 nm with nanosecond pulse, the limiting threshold of P1 was 728 mJ/cm2, and the throughput of P1 was limited to 344 mJ/cm2 for incident fluence as high as 1.1 J/cm2. The preliminary electroluminescent results and optical limiting effect of P1 suggested that P1 may be promising as light-emitting polymer and optical limiting material.