Physical and electrochromic properties of poly(2,5-dimethoxy aniline) synthesized in oxalic, nitric, and hydrochloric acids

Abstract

One of the promising electrochromic polymers is polyaniline, which possess a high environmental stability and fast response time. Nonetheless, the low solubility in common organic solvents restricts processibility. A derivative of polyaniline, poly (2,5-dimethoxy aniline) or PDMA, shows higher solubility and a faster response time than polyaniline. In this work, poly (2,5-dimethoxy aniline) was electrochemically deposited on flexible indium tin oxide in oxalic, nitric and hydrochloric acids at various dipping times. Under different applied potentials, the optical contrast and response time of the PDMA coated plastic indium tin oxide were determined by a UV-visible Spectro electrometer. The fastest response times in all acids occurred at 3.5 volts, where the response time was only 3.7 seconds in case of 6 minutes synthesis of PDMA in hydrochloric acid. The Fourier transform infrared (FTIR) spectroscopy indicated that the structure of PDMA coating via three acids were nearly the same except that the FTIR spectrum of PDMA from nitric acid showed an absorption peak at 1384 cm-1 representing N-O vibration. The thermal stability of the electropolymerized PDMA films was investigated via thermogravimetric analysis and showed similar three steps of weight loss at ~160 °C, 310 °C, and 450 °C. The surface morphology of PDMA coating depended on the type of acids used for the electro polymerization process.