Novel stoichiometric (1:1) complexes between the anionic conducting polymer poly(2-methoxyaniline-5-sulfonic acid) (PMAS) and a range of cationic ammonium surfactants have been prepared and characterized. The supramolecular PMAS–surfactant complexes are stable in chloroform and ethanol solutions, in which the PMAS moiety adopts an ‘extended coil’ conformation. Thin films of the complexes can be cast onto indium tin oxide-coated glass from these solutions. The application of an appropriate applied potential leads to redox switching of the PMAS from the emeraldine salt form to its pernigraniline and leucoemeraldine oxidation states. Immersion of the PMAS–surfactant films in 1.0 M NaOH causes the PMAS moiety to undergo conversion into a ‘compact coil’ conformation rather than alkaline de-doping to the emeraldine base form. When the PMAS–surfactant complexes are dissolved in polar organic solvents such as N,N-dimethylformamide, N-methylpyrrolidinone, and acetone, they undergo marked solvatochromism, which is interpreted in terms of rearrangement of the PMAS polymer chains from an ‘extended coil’ to a ‘compact coil’ conformation.