Poly(2-chloromethyl-2,3-dihydrothieno[3,4-b][1,4]dioxine), a chloromethyl functionalized poly(3,4-ethylenedioxythiophene) derivative (PEDOT-MeCl), was synthesized electrochemically via the potentiostatic polymerization of its monomer in dichloromethane solution containing suitable tetrabutylammonium tetrafluoroborate, then it was used for the characterization of film properties and the fabrication of electrochemical sensor. The properties of the resulting PEDOT-MeCl film were characterized by different methods such as cyclic voltammetry, electrochemical impedance spectroscopy, Fourier transform infrared and ultraviolet-visible techniques, scanning electron microscope, and thermogravimetric analysis. The PEDOT-MeCl film displayed a good reversible redox activity, remarkable capacitance properties, good thermal stability, rough, and porous structure, especially fluorescent spectra indicated that PEDOT-MeCl was a blue-emitter with maximum emission centered at 396 and 398 nm. Finally, the PEDOT-MeCl film was employed for the fabrication of the sensing electrode, and dopamine was chosen as a model analyte for the application of the electrochemical sensor. Results indicated that the PEDOT-MeCl film as sensing interface was feasible, and studies of these film properties were very beneficial for studying properties and applications of other poly(3,4-ethylenedioxythiophene) derivative films. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2660-2670, 2013