Web Release Date: February 9,
Highly Stable Anodic Electrochromic Aromatic Polyamides Containing N,N,N',N'-Tetraphenyl-p-Phenylenediamine Moieties: Synthesis, Electrochemical, and Electrochromic Properties
and
Institute of Polymer Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan, Republic of China, and Department of Applied Chemistry, National Chi Nan University, 1 University Road, Nantou Hsien 54561, Taiwan, Republic of China
Received September 26, 2007
Revised Manuscript Received December 20, 2007
Abstract:
A new triphenylamine-containing aromatic diamine, N,N-bis(4-aminophenyl)-N',N'-di(4-methoxylphenyl)-1,4-phenylenediamine (4), was successfully synthesized by the cesium fluoride-mediated condensation
of 4-amino-4',4' '-dimethoxytriphenylamine with 4-fluoronitrobenzene, followed by palladium-catalyzed hydrazine
reduction of the dinitro intermediate. A series of novel polyamides with pendent 4,4'-dimethoxy-substituted
triphenylamine (TPA) units having inherent viscosities of 0.28-0.80 dL/g were prepared via the direct
phosphorylation polycondensation from the diamine (4) and various dicarboxylic acids. All the polymers were
amorphous with good solubility in many organic solvents, such as N-methyl-2-pyrrolidinone (NMP) and N,N-dimethylacetamide (DMAc), and could be solution-cast into tough and flexible polymer films. These aromatic
polyamides had useful levels of thermal stability associated with their relatively high softening temperature (242-282 
C), 10% weight-loss temperatures in excess of 510 C, and char yields at 800 C in nitrogen higher than
63%. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium-tin oxide (ITO) coated
glass substrate exhibited two reversible oxidation redox couples at 0.47-0.51 and 0.82-0.86 V vs Ag/AgCl in
acetonitrile solution. The polyamide films revealed excellent stability of electrochromic characteristics, with a
color change from colorless or pale yellowish neutral form to green and blue oxidized form at applied potentials
ranging from 0.00 to 0.98 V. These anodically polymeric electrochromic materials not only showed excellent
reversible electrochromic stability with good coloration efficiency of green (CE = 285 cm2/C) and blue (CE =
272 cm2/C) but also exhibited high contrast of optical transmittance change (
T %) up to 60% at 430 nm and
73% at 1035 nm for green, and 86% at 850 nm for blue. After over 1000 cyclic switches, the polymer films still
exhibited excellent stability of electrochromic characteristics.
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