Donor-acceotor copolymers for red- and near-infrared-emitting polymer light-emitting diodes

We report a comparative study of two organic soluble, vinylene-based, alternating donor-acceptor copolymers with 1,4-(2,5-dihexadecyloxyphenylene) as the donor; the acceptor is either a 2,5-linked pyridine or a 5,8-linked 2,3-diphenylpyrido[3,4-b]pyrazine. The polymers are synthesized via a Heck coupling methodology from a dihalo monomer and a divinyl monomer to yield number-average molecular weights of 16,000 g/mol for the pyridine polymer (PPyrPV) and 6500 g/mol for the pyridopyrazine polymer (PPyrPyrPV), with high solubility in common chlorinated solvents and lower solubility in less polar solvents (e.g., tetrahydrofuran). Thin-film measurements show band gaps of 2.2 and 1.8 eV for PPyrPV and PPyrPyrPV, respectively. Both polymers exhibit photoluminescence in solution and in the solid state and exhibit electroluminescence when incorporated into light-emitting diodes. In this case, a broad red emission centered at 690 nm for PPyrPV and a near-infrared emission centered at 800 nm for PPyrPyrPV have been observed. (c) 2005 Wiley Periodicals, Inc.