Redox-active and electrochromic poly(amide-imide)s derived from Imide ring-preformed dicarboxylic acids and triphenylamine-based aromatic diamines

Two series of electroactive poly(amide-imide)s (PAIs) were synthesized using the phosphorylation polyamidation technique, employing various imide ring-preformed dicarboxylic acids in combination with two triphenylamine (TPA)-based diamine monomers: 4,4’-diamino-4”-methoxytriphenylamine (MeO-TPA-2NH₂) and N, N’-di(4-aminophenyl)-N, N’-di(4-methoxyphenyl)-1,4-phenylenediamine [(MeO)₂-TPPA-2NH₂]. All PAIs demonstrated excellent solubility in polar organic solvents and could be processed into strong, flexible films via solution casting. The fully aromatic PAIs exhibited high glass transition temperatures (T_g) exceeding 300 °C and did not show significant decomposition until reaching 500 °C. The incorporation of methylene units into the PAI main chain resulted in decreased T_g and thermal stability. The PAIs derived from the diamine monomer MeO-TPA-2NH₂ displayed reversible redox processes, changing color from colorless to green upon oxidation. In contrast, the PAIs based on the diamine monomer (MeO)₂-TPPA-2NH₂ revealed two reversible redox processes, accompanied by color changes from colorless in the neutral state to green and blue in the oxidized states. Both series of PAIs exhibited remarkably high electrochemical and electrochromic switching stability.