Phenothiazine Conjugated Polymer Synthesis And Characterization

Phenothiazine-based conjugated polymers with different functional groups in the main chain were designed and synthesized through Knoevenagel, Wittig and Heck condensations respectively. The polymers were characterized by ~1H-NMR, IR, UV-vis, FL, GPC and TG The influence of different functional groups in the main chain on the thermal stability and photophysical properties was investigated. TG result indicated that polymer PQP is the most thermally instable one among all the polymers, which considered to be resulted from the formation of a quinoid structure with a longer conjugated length from p-phenylene. On the contrary, the formation of a quinoid structure from m-phenylene is incapable, and the introduction of a cyano group just made the intermolecular interaction enhanced, which resulted in a large increase in thermal stability for polymer PQM. Additionally, polymer PQDN is the most thermally stable one. The absorption maxima of the polymers with electron-deficient units in the main chain, i.e. polymers PQP, PQM, PQDN, PQTN, PQS and PQSe, were all largely red-shifted compared with that of polymer PQ as determined by UV-vis spectra of the polymers in THF dilute solution. FL spectra in THF dilute solution of the polymers showed narrow FWHMs, illustrating that these polymers may be suitable as pure light-emitting materials. In addition, polymers PQS and PQSe are believed as good candidates for photovoltaic applications due to their low band gap.Several OLED devices with a single-layer or double-layer structure were fabricated using part of the polymers prepared as an active layer. The electroluminescence properties of the devices were investigated, and the influence of the operating voltages on electroluminescence spectra was also discussed. Results suggested that the electroluminescence spectra of the devices under different voltages were almost unchangeable, which indicated that these OLED devices have a stable emission property. Fortunately, OLEDs from PQTN could emit an orange-red light and the maximum luminance reaches up to 2430 cd/m~2.