PEDOT layers are synthesized in aqueous solutions in the presence of one of the three different anionic species - polysterenesulfonate (PSS), poly(2-acrylamido-2-methyl-1-propane-sulfonate) (PAMPS) and dodecylsulfate without any addition of further inorganic anions. Simultaneous electrochemical and acoustic admittance measurements are carried out in the course of polymerization. The data from the admittance spectra are used to extract information on the mechanical shear storage and loss moduli of the three types of PEDOT layers. The anionic species are found to affect the polymerization kinetics, the surface morphology and most markedly the viscoelastic properties of the three types of layers. The latter depend primarily on the innate structure arising in the course of polymerization whereas the solution specifics play a secondary role. Dodecylsulfate imparts significant stiffness to the PEDOT layers with high rigidity preserved for relatively large polymerization charges. The G moduli in this case exceed 10(9) dyn/cm(2). Both polyanion-doped PEDOT layers are found to be softer but there is nevertheless a clear difference between them with PEDOT/PAMPS having a strong predisposition for swelling. (C) 2013 Elsevier Ltd. All rights reserved.