Fluorine-substituted poly(p-phenylenes vinylenes) copolymers

We report the electrochemical, optical, and electroluminescent properties o f fluorine containing poly(phenylene vinylene) random copolymers. We used 2 ,3,5,6-tetrafluoro-1,4-phenylene vinylene and 2-methoxy-5-(2'-ethyl-hexylox y)-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 pi -electron system was confirmed by electrochemical mea surements, 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, w ith lower turn-on voltages and higher electroluminescence efficiencies for lower fluorine contents. We observed maximum photoluminescence efficiencies of 6.7%. (C) 2001 Elsevier Science B.V. All rights reserved.