Hp. Welzel et al., Reactive groups on polymer-covered electrodes 11. Copolymerization of methyl thiophene-3-acetate with 3-alkylthiophenes, J SOL ST EL, 5(2), 2001, pp. 141-149
Polythiophene films containing ester groups on the surface of electrodes ar
e interesting potential carrier materials for reagents. Methyl thiophene-3-
acetate (3) can be copolymerized with 3-methylthiophene (1) and 3-butylthio
phene (2) by means of cyclic voltammetry (CV) at potentials of 0-2.2 V. Hig
her potentials (0-2.4 V) lead to overoxidation of the copolymers. The eater
groups were confirmed by FTIR spectra. Electrochemical investigations of 2
,2'-bithiophene (6) and 3 at equimolar ratios showed no successful copolyme
rization at potentials of 0-1.3 V, If the copolymerization experiments of 6
with 1 or 3 were carried out at molar ratios of 1:50 at 1.3 V, 6 with its
low oxidation potential was polymerized without copolymerization of the oth
er monomers. However, if the oxidation potential was increased stepwise fro
m 1.3 V, the oxidation of 1 or 3 occurred, forming copolymers containing bo
th monomer components. HPLC investigations of solutions containing mixtures
of 6 and 3 and also 6 and 1 in acetonitrile/TEABF(4) showed, after exhaust
ive oxidation at a potential of 1.3 V, the complete absence of 6. 1 and the
eater 3 were not oxidized and copolymerized at these potentials. From the
results of the copolymerization experiments, as well as the HPLC investigat
ions, it can be concluded that the dominant mechanism of the electrochemica
l polymerization is radical cation dimerization.