A new series of copolymers with high brightness and luminance efficiency were synthesized using the Gilch polymerization method, and their electro-optical properties were investigated. The weight-average molecular weights (M w ) and polydispersities of the synthesized poly(9,9-dioctylfluorenyl-2,7-vinylene) [poly(FV)], poly[2-(3-dimethyldodecylsilylphenyl)-1,4-phenylenevinylene] [poly(m-SiPhPV)], and poly[9,9-di-n-octylfluorenyl-2,7-vinylene]-co-(2-(3-dimethyldodecylsilylphenyl)-1,4-phenylene vinylene)] [poly(FV-co-m-SiPhPV)] were found to be in the ranges of (8.7-32.6) Â 10 4 and 2.3-5.4, respectively. It was found that the electro-optical properties of the copolymers could be adjusted by controlling the feed ratios of the comonomers. Thin films of poly(FV), poly(m-SiPhPV), and poly(FV-co-m-SiPhPV) were found to exhibit photoluminescence quantum yields between 21% and 42%, which are higher than those of MEH-PPV. Light-emitting diodes were fabricated in ITO/PEDOT/light-emitting polymer/cathode configurations using either double layer (LiF/Al) or triple layer (Alq 3 /LiF/Al) cathode structures. The performance of the polymer light-emitting diodes (PLEDs) with triple layer cathodes was found to be better than that of the PLEDs with double layer cathodes in poly(FV) and poly(FV-co-m-SiPhPV). The turnon voltages of the PLEDs were in the range of 4.5-6.0 V, with maximum brightness and luminance efficiency up to 9691 cd/m 2 at 16 V and 3.27 cd/A at 13 V, respectively.

Substituent‐induced electroluminescence polymers—poly[2‐(2‐dimethyldodecylsilylphenyl)‐1,4‐phenylenevinylene] [(o‐R3Si)PhPPV], poly[2‐(3‐dimethyldodecylsilylphenyl)‐1,4‐phenylenevinylene] [(m‐R3Si)PhPPV], and poly[2‐(4‐dimethyldodecylsilylphenyl)‐1,4‐phenylenevinylene] [(p‐R3Si)PhPPV]—were synthesized according to the Gilch polymerization method. The band gap and spectroscopic data were tuned by the dimethyldodecylsilyl substituent being changed from the ortho position to the para position in the phenyl side group along the polymer backbone. The weight‐average molecular weights and polydispersities were 8.0–96 × 104 and 3.0–3.4, respectively. The maximum photoluminescence wavelengths for (o‐R3Si)PhPPV, (m‐R3Si)PhPPV, and (p‐R3Si)PhPPV appeared around 500–530 nm in the green emission region. Double‐layer light‐emitting diodes with an indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polymer/Al configuration were fabricated with these polymers. The turn‐on voltages and the maximum brightness of (o‐R3Si)PhPPV, (m‐R3Si)PhPPV, and (p‐R3Si)PhPPV were 6.5–8.7 V and 1986–5895 cd/m2, respectively. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2347–2355, 2004

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