Redox-Induced Reversible Conformational Switching of Poly(aniline sulfonic acid) with Transition Metals in Aqueous Solution

Redox-induced reversible conformational switching of poly(aniline sulfonic acid) (PAS) with transition metals in aqueous solution was studied. (ES)PMAS was deionized through cation-exchange resins before use. The redox interaction was mainly studied by UV-vis-NIR spectrometry in pH 8.8. The conformation was determined by the corresponding diagnostic peak to each conformation. The sharp peak around 475 nm attributed to the polaron band was characteristic to the extended coil conformation. One equiv of various transition metals based on the aniline monomer unit was added to the stirred aqueous solution of (ES)PMAS with the extended coil conformation at room temperature under air. In the spectra, the polaron band at 471 nm decreased gradually, and completely disappeared after 2 h. The color changed from yellow/green to green within I mm, then blue within 10 mm. These results suggest that the reoxidation of CuI with 0 2 is involved for the conformational change.