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Various functionalized polythiophene films on electrode surfaces were produced by electropolymerization. Starting from 3-(2-hydroxyethyl)thiophene (1) different ether and ester derivatives were synthesized:  3-(2-(benzyloxy)ethyl)thiophene (2), 3-[2-((triphenylmethyl)oxy)ethyl]thiophene (3), 3-[2-((trimethylsilyl)oxy)ethyl]thiophene (4), 3-[2-((dimethyl-tert-butylsilyl)oxy)ethyl]thiophene (5), 3-(2-acetoxyethyl)thiophene (6), 3-(2-(benzoyloxy)ethyl)thiophene (7), 3-[2-((p-nitrobenzoyl)oxy)ethyl]thiophene (8), and 3-[2-((3,5-dinitrobenzoyl)oxy)ethyl]thiophene (9). Cyclovoltammetric analyses in acetonitrile with tetrabutylammonium perchlorate (TBAP) as supporting electrolyte gave the characteristic peak potentials (Ep's) of the electrochemical oxidation of these monomers. Under our standard conditions homopolymerization of the monomers 2−9 could not be achieved, whereas copolymerization of 2−9 with 3-methylthiophene (10) was successful. The resulting polymeric films were characterized by FT IR spectroscopy and chemical reactions.

Methylated bi- and terthiophenes (monomers, 1, 3, 5, 8) with one free α-position can be oxidized with FeCl3·6H2O. An irreversible dimerization reaction forms dimers of the expected structure. The radical cations of the monomers also react with free β-positions of the formed dimers (6, 9) having two methylated α-positions. The products of these reactions show α,β‘ linkages (7, 10, 11). Different β-positions in end-capped dimers show a graduated reactivity against radical cations of the monomers; the free β-position with the higher electron spin density can be attacked preferably by an α-position of a radical cation of a monomer molecule. No products with β,β‘ linkages were found. Electrochemical investigations using fast-scan voltammetry show the formation of α,α‘ linkages of methylated oligothiophenes. For bithiophene derivatives, rate constants of the dimerization process in the range of 10⁹ L·mol^-1·s^-1 were determined. In comparison with a terthiophene derivative, it was found that the dimerization rates decrease with increasing chain length of the oligomers.