Electrochromism of the composite film of ethylene-vinyl alcohol copolymer and polypyrrole

The composite film of ethylene-vinyl alcohol copolymer (EVOH) and polypyrrole (PPy) were prepared by the electrochemical polymerization of pyrrole on an EVOH film containing lithium perchlorate coated on Indium-tin oxide (ITO). When a potential was varied from -1.0 V to 1.0 V, the color of the composite film changed reversibly from yellow to brown. The difference in absorbance (Delta A, 0.0.1-0.15) at 800 nm between the application of 1.0 V and -1.0 V in UV/VIS spectra of the composite film did not exhibit a pronounced decrease until ca.7000 cycles. In contrast to this behavior, the Delta A of a single PPy film rapidly dropped with an increasing cycle number and approached 0 within ca. 1000 cycles. This result indicates that the durability against the repeated application of potentials markedly improved in the composite film.