The article presents the method of the synthesis of sulfonated polythiophene derivative (PTMBSA) in aqueous medium by means of emulsion polymerization. The method applies potassium peroxydisulfate as initiator and sodium dodecyl sulfate as the surfactant. The structure and physicochemical properties have been analyzed. Resulting polymers were characterized via Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), thermogravimetric analysis, UV‐VIS, and electrochemical methods (e.g., cyclic voltammetric, current‐voltage characteristics, doping processes). Resulting polymer revealed mixed electronic and ionic conductivity having solid state maximum conductivity σ = 5.061 μS m−1. It is four orders of magnitude higher than this of pristine polythiophene obtained by similar way. Presented results show that tested polymers are interesting and seem to be promising material for organic electronic applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44372.