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In this paper our recent advances in the development of a novel class of highly efficient DSB-segmented copolymers 1-51, 2, 3 have successfully been synthesized using the HORNER/WITflG carbonyl olefination of appropriate dialdehydes which are based on triphenylanñne, diphenylether, and diphenylketone. 4 was prepared by polymer analogous carbonyl reduction of 3. This approach resulted in highmolecular and soluble materials (Mn 10.000 -20.000) exhibiting green (1, 3) and blue (2, 3) hnninescence with an excellent photoluminescence efficiency (65 -90 % in solution). Our goal in this paper is to illustrate the changes in the electrooptical properties that have been caused by segmentation of the polyconjugated PPV backbone into distyrylbenzene (DSB) segments which are connected by mono-atomic V groups. The chemical character of Y determines significantly the oxidation potentials (LOX 0,66 V (1), 0,92 V (2), 1,15 V (3), 1,04 V (4), V vs. Ag/AgCl). Due to its low and reversible oxidation potential 1 shows the most favourable properties for low voltage LED's: green electroluminescence with luminance in the range of 100 -500 cd/rn2 at 7 -10 V has been demonstrated.There has also been prepared an electron donating polymer 5 having additional phenyl substituents attached to the vinylenic unit. These phenyl groups are responsible for high glass transition temperature (Tg 197°C) and helped to solubiize the chain.

We have studied the effects of using a composite fabricated from carbon nanotubes and a host polymer, poly͑m-phenylene-vinylene-co-2,5-dioctyloxy-p-phenylene-vinylene͒ ͑PmPV͒, as an electron-transport layer in organic light-emitting diodes. Double layer devices using this composite as an electron-transport layer, triple layer devices with a composite electron-transport layer, and poly͑9-vinylcarbazole͒ as a hole-transport layer, as well as poly͑2,5-dimethoxy-1,4-phenylene-vinylene-2-methoxy-5͑2Ј-ethylhexyloxy͒-1,4-phenylene-vinylene ͑M3EH-PPV͒ single layer devices were prepared. Current-voltage-luminance and electroluminescent spectral measurements were performed using six different nanotube powder to polymer mass ratios ͑0%, 2%, 4%, 8%, 16%, and 32%͒ for all device structures studied. dc transport and photoluminescence behavior of the polymer-nanotube composite were also investigated. Although a potential barrier is introduced at the M3EH-PPV/composite interface, a significant increase in efficiency was observed using the composite. The best efficiency was obtained for those devices with an electron-transport layer of mass ratio 8%. In addition, on doping with nanotubes, electron conductivity in the composite increased by over 4 orders of magnitude with little quenching of photoluminescence.

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