Novel Organosoluble Aromatic Polyimides Bearing Pendant Methoxy-Substituted Triphenylamine Moieties: Synthesis, Electrochromic, and Gas Separation Properties

Four series of polyimides I-VI with pendent triphenylamine (TPA) units having inherent viscosities of 0.44-0.88 dL/g were prepared from four diamines with two commercially available tetracarboxylic dianhydrides via a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids, followed by chemical cyclodehydration. These polymers were amorphous and could afford flexible films. All the polyimides had useful levels of thermal stability associated with high softening temperatures (279-300 degrees C), 10% weight-loss temperatures in excess of 505 degrees C, and char yields at 800 degrees C in nitrogen higher than 58%. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyimide films cast onto an indiumtin oxide (ITO)-coated glass substrate exhibited a or two reversible oxidation couples at 0.65-0.78 and 1.00-1.08 V versus Ag/AgCl in acetonitrile solution. The polymer films revealed electrochromic characteristics with a color change from neutral pale yellowish to blue doped form at applied potentials ranging from 0.00 to 1.20 V. The CO2 permeability coefficients (P-CO2) and permeability selectivity (P-CO2/P-CH4) for these polyimide membranes were in the range of 4.73-16.82 barrer and 9.49-51.13, respectively. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7937-7949, 2008