Physical properties of polyaniline films: Assembled by the layer-by-layer technique

Sequential addition of a polyanion, poly(styrene sulfonate), and a polycation, polyaniline, lead to the formation of layer-by-layer films at different solid surfaces. The prime variables which determine the films formation of poly(styrene sulfonate) (PSS)/polyaniline (PANI) were the polymer charge and, ionic strength. The films were deposited by selecting organic/inorganic acid media at pH 2.8. The building up of such multilayer films was characterized by the increment of the adsorbed amount through UV-visible spectroscopy. A linear increase in the absorption magnitude was measured from 1 to 25 bilayers. The uniformity of the PSS/PANI layer-by-layer (LBL) films could be well-maintained, undoping the films in NaOH for obtaining an emeraldine base form of polyaniline. The built-up multilayers were investigated by atomic force microscopy, scanning tunneling microscopy, and cyclic voltammetric and electrical conductivity measurements. The interesting feature of the nearly equal grain size was noticed between 4 and 15 bilayer films of PSS/PANI. The surface roughness was distinguished beyond 15 bilayers of LBL films, The cyclic voltammogram showed the change in the peaks potential value going from 1 to 20 bilayers. The inhomogeneity incorporated inside the films slowed down the electrochemical kinetics in the PSS/ PANI bilayers while going from 1 to 25 bilayer films. The diffusion coefficient (D-0) of PSS/PANI 10 bilayers was estimated to be 2 x 10(-8) cm(2) s(-1). Such multilayer films exhibit conductivity in the area of 0.1 S/cm.