Fluorine-substituted poly(p-phenylenes vinylenes) copolymers

We report the electrochemical, optical, and electroluminescent properties of fluorine containing poly(phenylene vinylene) random copolymers. We used 2,3,5,6-tetrafluoro-1,4-phenylene vinylene and 2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene moieties, with ratios of the two copolymer units varying between 5:95 and 27:75. The electron withdrawing effect of fluorine on the conjugated π-electron system was confirmed by electrochemical measurements, which showed an increase of the oxidation and a decrease of the reduction potentials, upon increase of the fluorine content. Light emitting diodes fabricated from the copolymers showed emission in the red-orange, with lower turn-on voltages and higher electroluminescence efficiencies for lower fluorine contents. We observed maximum photoluminescence efficiencies of 6.7%.