n-Type Polyimides with 1,3,4-Oxadiazole-Substituted Triphenylamine Units-An Innovative Structural Approach

摘要

A novel aromatic diamine containing 1,3,4-oxadiazole-substituted triphenylamine (TPA) was successfully synthesized and structurally characterized. Based on this, a series of three aromatic polyimides with high thermal stability were prepared and processed in thin coatings with a grain-like morphology. Their ability to form a dual intramolecular charge transfer complex between TPA and 1,3,4-oxadiazole in the side chain and TPA and phthalimide in the main chain was proven. Both the optical effects and electronic properties were found to be modulated by the competing electron-withdrawing character of 1,3,4-oxadiazole/imide units. The electrochemical investigation suggested their n-type redox capability and electron transporting characteristics, a statement supported by current-voltage measurements of some indium tin oxide/poly(3,4-ethylenedioxythiophene): polystyrene sulfonate/polyimide/eGaIn prototype devices. Thereby, the present polyimides enable the pathway toward alternative n-type materials currently used in optoelectronics devices.