Monoparticulate films of polyaniline

Monoparticulate films were prepared from colloidal polyaniline (PANI) via the Langmuir–Blodgett (LB) technique. An aqueous dispersion of PANI obtained by aniline polymerization in the presence of polyvinyl alcohol was spread at the air–water interface in a LB trough. The floating films were transferred by the vertical lifting method to Si wafer or glass substrates. The films were very stable and could not be removed during immersion in aqueous solutions for at least several months. The color of dry monoparticulate PANI films was violet independently of the color adapted upon immersion in aqueous media at different pH. We suggest that not only the wavelength of the absorbed light, but also that of the scattered light, has an effect on the color of PANI.