Copolymers of aniline (ANI) and 2-methoxyaniline (MOA) in variable ratios, as well as the corresponding homopolymers, were electrosynthesized and characterized by elemental analysis, IR spectroscopy, and direct laser desorption ionization. The resulting copolymer composition obtained from the analysis was correlated with the feed composition through the Mayo–Lewis equation, confirming the higher reactivity of MOA. The electrochemomechanical behaviour was studied through direct microscopical observation of the volume changes caused by redox switching in sulphuric and perchloric acid media. It was found that the freshly electropolymerized films had, for the same voltammetric charge, smaller volume as the MOA/ANI ratio increased. The volume changes observed during the first cycle where consequently strongly dependent on the polymer composition, but also on the electrolyte anion. The stationary cycle changes showed less dependence on both. The behaviour reveals different anion/polymer interactions as the copolymer composition is changed. From the perspective of mechanical applications the ANI–MOA copolymers, for most of the composition range, did not show marked differences compared with poly(aniline), thus being materials with similar characteristics to this homopolymer but being more processable.