New Luminescent PPV Derivatives for Led Applications
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phenylene ring. We were interested in the effect of 2,3-dialkoxy substitution on the properties of PPV derivatives [6].
We present in this paper the synthesis of the poly(2,3-dibutoxy-l,4-phenylenevinylene) [PDB-PPV] 8 having the unconventionally positioned dialkoxy substituents on the phenylene ring of the PPV backbone, using the Gilch dehydrohalogenation [7] route. The characterization and observation of significantly blue-shifted emission properties in both PL and EL devices are reported, together with supporting information on the crystal structure of the model oligomer 11. RESULTS Synthesis of the Polymer PDB-PPV 5 The monomer was synthesized using the method outlined in Scheme 1. Alkylation of the bis phenol 3 using the Mannich reagent derived from 1 and 2 afforded the morpholino derivative 4 [8]. This underwent transfer hydrogenolysis [9] using Pearlman's catalyst to yield the dimethyl catechol 5. The catechol derivative was O-alkylated to produce the dibutoxy-xylene 6 which underwent side chain bromination [10] using N-bromosuccinimide in tetrachloromethane to give the bis(bromomethyl) monomer 7. The polymerization of the bis(bromomethyl) benzene 7 was carried out in tetrahydrofuran (THF) at room temperature using excess potassium t-butoxide to ensure a high degree of dehydrohalogenation. It was found (elemental analysis) that six equivalents of potassium tertbutoxide yielded
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