Preparation and characterization, stable bismaleimide-triarylamine polymers with reversible electrochromic properties

A series of novel polyimides were synthesized from bismaleimide containing different diaminetriarylamines by Michael addition reaction. The prepolymer is readily soluble in many common organic solvents, such as CHCl₃, Tetrahydrofuran (THF) and N, N-dimethyl formamide (DMF). Prepolymers can be solution-cast into transparent, tough, and flexible films. These aromatic polyimides display good thermal stabilities, i.e. 5% weight-loss temperatures in excess of 200 C under nitrogen. All obtained polyimides revealed excellent stability of electrochromic characteristics, changing color from original yellowish to green. The energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of the investigated the polymers were estimated by experimental method are in the range of -4.78 eV to -4.98 eV and -1.64 eV to -2.09 eV vs the vacuum level, respectively. All the polymer films reveal good electrochemical and electrochromic stability under repeatedly switching electrode voltages, with coloration change from the yellow neutral state to green oxidized state.