Efficient synthesis of benzobisazole terpolymers containing thiophene and fluorene?

Polymer Chemistry Pub Date: 2011-07-18 DOI: 10.1039/C1PY00218J

Abstract

We report the synthesis and lumuminescence properties of three novel polymers composed of 9,9-dioctylfluorene and a donor–acceptor-donor (D–A-D) triad of a benzobisazole moiety sandwiched between two octylthiophenes. The requiste monomers, 2,6-bis(5-bromo-3-octylthiophen-2-yl)-benzobisazoles were obtained efficiently via the Lewis acid catalyzed cyclization of 2-bromo-3-octyl-5-(triethoxymethyl)thiophene and the corresponding diamino diols or dithiols. The polymers were synthesized in excellent yield by the Suzuki coupling reaction between the D–A-D benzobisazole monomers and 9,9-dioctylfluorene bisboronic acid. Alkyl side chains provided the polymers with solubility in common organic solvents, enabling characterization using gel permeation chromatography, 1H NMR, UV-Vis and fluorescence spectroscopy. The polymers have optical bandgaps of 2.43–2.63 eV and HOMO levels at ?5.54 to ?5.65 eV relative to vacuum as determined by UV visible and photoelectron spectroscopy respectively. Light-emitting diodes using blends of the copolymers in a poly(N-vinyl carbazole) matrix yielded blue-green emission with luminous efficiencies of 0.86 Cd/A at ～505 nm. This efficient and high-yielding route is a promising approach for the synthesis of polymers containing benzobisazole moieties.

Graphical abstract: Efficient synthesis of benzobisazole terpolymers containing thiophene and fluorene
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