Electrochemical properties of non-conjugated electrochromic polymers derived from aromatic amine derivatives

The electrochemical and optical properties of two types of non-conjugated electrochromic polymers derived from aromatic amine derivatives (DDP-A, DDB-P) are presented. DDP-A is synthesized by the polymerization of N,N'-dimethyl-N,N'-diphenyl-1,4-phenylenediamine (DDP) and acetaldehyde (A), and DDB-P is polymerized with N,N'-dimethyl-N,N'-diphenylbenzidine (DDB) and propionaldehyde (P). Both DDP-A and DDB-P have a band gap in the ultraviolet region, and are colorless and transparent in neutral states. At one-electron oxidation states, DDP-A(.+) absorbs light mainly in a Visible region, whereas DDB-P.+ absorbs light mainly in a near-infrared (NIR) region. DDP-A(.+) and DDB-P.+ are nitrogen-centered rr-bridged mixed-valence compounds showing intervalence-charge transfer bands. The electrochemical and optical properties of DDP-A and DDB-P depend on the nitrogen-nitrogen distance correlating the electronic coupling of nitrogen redox centers. From the standpoint of energy saving, DDB-P is very interesting because it absorbs light in an NIR region. Finally, focusing on the smart window application, the optical properties of the solid-state electrochromic cell fabricated with DDP-A and heptyl viologen are examined. The cell was confirmed to be colored blue by applying a potential of about 1.0 V, and bleached at 0 V. (C) 2001 Elsevier Science Ltd. All rights reserved.