Synthesis and characterization of new redox-active and electrochromic polyimides with (4-morpholinyl)triphenylamine units

• New polyimides with (4-morpholinyl)triphenylamine units were prepared.
• The polymers showed high redox-activity and good electrochemical stability.
• The polymer films exhibited p-doping and multi-electrochromic behavior.

A series of electroactive aromatic polyimides with (4-morpholinyl)triphenylamine units in the backbone were prepared from a newly synthesized diamine monomer, 4,4′-diamino-4″-(4-morpholinyl)triphenylamine, and aromatic tetracarboxylic dianhydrides via the conventional two-step polycondensation technique. Flexible and tough polyimide films could be obtained via the thermal curing of their precursor poly(amic acid) films. The polyimides showed high glass-transition temperatures (Tg) between 290–313 °C, and they did not show significant decomposition before 500 °C in air or nitrogen atmosphere. Cyclic voltammograms of the polyimide films on the indium-tin oxide (ITO)-coated glass substrate exhibited a pair of reversible oxidation waves with low onset oxidation potentials of 0.43–0.53 V (vs. Ag/AgCl) in acetonitrile solution. They also exhibited multicolor electrochromic behavior between their neutral and oxidized states changing from pale yellow to cyan and bluish purple.

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