Poly[(2‐alkoxy‐5‐methyl‐1,3‐phenylene vinylene)‐alt‐(phenylene vinylene)] derivatives with different contents ofcis‐ andtrans‐olefins: The effect of the olefin bond geometry and conjugation length on luminescence

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Abstract
Poly[(2‐alkyloxy‐5‐methyl‐1,3‐phenylenevinylene)‐alt‐(1,3‐phenylenevinylene)]s (8) and poly[(2‐alkyloxy‐5‐methyl‐1,3‐phenylenevinylene)‐alt‐(1,4‐phenylenevinylene)]s (10) were synthesized by the Wittig reaction to provide materials containing 45–62%cis‐vinylene bonds. The optical characteristics of8and10were compared with those of their respective isomers,3and4, thecis‐vinylene contents of which were significantly lower (9–16%). Although a greater fraction ofcis‐CHCH linkages caused the absorption maximum (λmax) of8and10to be slightly blueshifted (by ∼3–6 nm) from that of3and4, the impact of the vinylene bond geometry appeared to be negligible on their fluorescence spectra. The fluorescence quantum efficiencies of8and10were estimated to be approximately 0.25 and 0.72, respectively. Both8(λmax≈ 445 or 462 nm) and10(λmax≈ 480 or 506 nm) were electroluminescent, showing effective color tuning by the controlled insertion ofm‐phenylene moieties. The external electroluminescence quantum efficiencies were determined to be 4.26 × 10−3% for8and 0.63% for10. Thecis/trans‐vinylene bond ratio had a great impact on the electroluminescence device performance of8but a much smaller impact on the performance of10. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 303–316, 2004