Conjugated copolymers bearing 2,7-dithienylphenanthrene-9,10-dialkoxy units: highly soluble and stable deep-blue emissive materials

Conjugated copolymersPNP1-4were prepared from the palladium catalyzed Suzuki-Miyaura cross-coupling reaction of 2,7-dithienylphenanthrene units - bearing various alkoxy groups -PNM1-4and 9,9-dioctylfluorene-2,7-diboronic acidFBA. The formation of copolymersPNP1-4was confirmed by different analytical techniques, such as, gel permeation chromatography (GPC), thermogravimetry analysis (TGA),¹H- and¹³C-nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), UV-vis absorption and emission spectroscopies. The target copolymers were found to have a relatively high thermal and chemical stability as well as an excellent solubility in common organic solvents. GPC traces of copolymersPNP1-4display noticeably large weight-average (M_w) molecular weights in the range of 36.5-152.0 kDa and a polydispersity index (Đ=M_w/M_n) of 2.5-3.0. Photophysical analysis ofPNP1-4divulges their luminescence in the deep blue region, namely, in the range of 453-463 nm with an emission quantum yield up to 17%. In addition, copolymersPNP1-4were explored as field-effect transistors revealing a hole mobility up to ∼6.4 × 10⁻⁶cm²V⁻¹s⁻¹.