Humidity-switch chromism of aniline-pentamer in Nafion

Abstract

Aniline-pentamer (AP) in Nafion triggered with humidity content displays an interesting chromism from blue to pink, which is much wider of color shift than general polyaniline. Thermogravimetric analysis confirms the reversal color change related to the moisture content in the sample. IR absorption spectra make known AP having high degree of protonation at lower water content. UV-Vis absorption expose the chromism process having something more than just protonation. The change of electronic energy levels and PL spectra reveal that there must be a complex interaction in NaAP. Raman scattering mapping confirms that drying causes the - SO3- hydrophilic channels transforming to isolated domains dispersed in matrix, which induces heavy protonation and complexation of AP with - SO3- groups. We can infer that the interesting humidity-switch chromism is due to the reversible protonation/deprotonation as well as complexation of AP with - SO3- groups through the reversible change of Nafion\'s morphology.