Near infrared electrochromic naphthalene-based polyimides containing triarylamine: Synthesis and electrochemical properties

A series of novel multicolored near-infrared (NIR) electrochromic aromatic polyimides (PIs) have been synthesized by a conventional two-step polymerization process. The structures of PIs were characterized by means of Fourier transform infrared (FTIR), H-1 NMR spectroscopy, which showed an agreement with the proposed structure. These poly (amic acid)s have inherent viscosities of 0.75-0.84 dl/g. They are readily soluble in many organic solvents, such as N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). All PIs displayed outstanding thermal stabilities, i.e. 5% wt loss in excess of 480 degrees C under nitrogen. The highest-occupied molecular orbital (HOMO) and lowest-unoccupied molecular orbital (LUMO) energy levels of these PIs were determined in the range of -4.95 to -5.00 and -1.97 to -2.01 eV (vs the vacuum level) by cyclic voltammetry method which were consisting with the results of quantum chemical calculation well, respectively. All obtained PIs revealed stability of electrochromic characteristics, changing color from original yellowish to red and blue. In addition, the PIs films showed high coloration efficiency (CE), short switching time, and anodic electrochromic behavior. The properties prove that the PIs are multipurpose materials which will be subject of hole-transporting and electrochromic application in the near future. (C) 2013 Elsevier Ltd. All rights reserved.