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

Sequential addition of a polyanion, poly(styrene sulfonate), and a polycati on, 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 a nd, ionic strength. The films were deposited by selecting organic/inorganic acid media at pH 2.8. The building up of such multilayer films was charact erized by the increment of the adsorbed amount through UV-visible spectrosc opy. A linear increase in the absorption magnitude was measured from 1 to 2 5 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 at omic force microscopy, scanning tunneling microscopy, and cyclic voltammetr ic 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 fil ms, The cyclic voltammogram showed the change in the peaks potential value going from 1 to 20 bilayers. The inhomogeneity incorporated inside the film s 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/PA NI 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.