Conjugated polymers containing electron-deficient main chains and electron-rich pendant groups: Synthesis and application to electroluminescence

Two novel conjugated polymers denoted TAZF2 and TAZBTF, having electron-deficient main chains and electron-rich triphenylamine pendant groups, were designed and synthesized. While TAZF2 was constructed with fluorene and electron-deficient 1,2,4-triazole as the major components of the main chain, fluorene, 1,2,4-triazole, and 2,1,3-benzothiadiazole were employed to form TAZBTF. The number-average molecular weights (M-w) of the polymers fell in the range of 1.28 x 10(4)-2.56 x 10(4) with polydispersity indexes (PDI = M-w/M-n) of 1.49-1.95. The polymers had glass transition temperatures (T-g) in the range of 153-185 degrees C. While TAZF2 exhibited blue photoluminescence, TAZBTF exhibited yellow-green emission. Thermal stability of the conjugated polymers was enhanced due to the introduction of rigid bipolar components. The incorporation of 2,1,3-benzothiadiazole into TAZBTF reduced the coplanarity of the conjugated polymer, which prohibited the polymer from aggregation. Intramolecular and intermolecular energy transfer was clearly evidenced by the shift in light emission to the yellow-green region. TAZBTF exhibited maximum electroluminescence efficiency as high as 2.60 cd/A, demonstrating that a good balance of charge carriers is injected into our devices. (C) 2011 Elsevier B.V. All rights reserved.