Ortho-CATENATION and trifluoromethyl graphting as driving forces in electro-optical properties modulation of ethanol soluble triphenylamine-based polyimides. (April 2019) - Constantin, Catalin-Paul
Abstract: A novel aromatic trifluoromethyl (CF3 )-substituted triphenylamine (TPA)-based diamine was synthesized and subjected to polycondenstion with various commercial aromatic dianhydrides. The obtained polyimides exhibit excellent solubility in common organic solvents, including ethanol, allowing their processing in thin films under environmentally friendly conditions. These polymers possess superior thermal stability, up to 485 °C and high glass transition temperature. The photo-optical properties were investigated in detail and the results evidenced the existence of a dual intramolecular charge transfer (ICT) between TPA and CF3 units, on one hand and triphenylamine and phthalimide, on the other hand, a feature rarely encountered at TPA-based polyimides. The occurrence of the FRET mechanism between these two ICT exited states that modulates the light emission toward yellow-orange spectral range is a totally novel aspect highlighted for this type of polymers. Prototype devices with ITO/PEDOT:PSS/polyimide/Ag configuration were also fabricated and preliminary investigations of the electrical characteristics were performed. Graphical abstract: Highlights: Triphenylamine-based polyimides with excellent organosolubility are synthesized. The polymers possess high thermal stability, up to 485 °C and high Tg . Yellow-orange emission was achived due to the FRET mechanism. The developed polyimides proved the ability for ambipolar transport characteristics. Nonlinear Schottky behaviour was demonstrated in ITO/PEDOT:PSS/polyimide/Ag devices.