Thiophene monomers displaying a dimethylenecarboxylate (CH2CH2COOR) substituent on the 3-position of the aromatic ring can be easily obtained and in one step from the electrochemically induced reaction of 3-bromothiophene with the corresponding acrylate (CH2?CHCOOR). The synthesis of the ethyl ester monomer, of related 2,5-dihalogenothiophenes, and their polymerization are reported. Despite the surprisingly low solubilities displayed by the polymers, a full spectroscopic characterization could be performed and the data fully analyzed. Oxidative polymerizations (FeCl3 or electropolymerization) yield a regioirregular polythiophene, with 6070% of head-to-tail diads. Both experimental and theoretical results suggest that the nonconjugated ester plays a very minor roleif anyin the polymerizations under oxidative conditions, but has a significant influence on the polymer properties. Preliminary attempts to polymerize the dihalogenothiophenes under reductive conditions were hampered by the even lower solubilities exhibited by the regioregular oligomers. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012