Synthesis and electrochemical polymerization of poly [3-(1-naphthylthiophene)]

3-(1-naphthylthiophene) was synthesized by a coupling reaction of a 1-naphthyl Grignard reagent with 3-bromothiophene, catalyzed by Ni(II) catalyst. Cyclic voltammetry of a 17 mM 3-(1-naphthyithiophene), 0.1 M Et4NBF4/acetonitrile solution yields an oxidation wave at about 1.2 V which corresponds to the formation of the radical cation. Galvanostatic deposition of poly [3-(1-naphthylthiophene)] was carried out at a current density of 12.5 mA/cm2 and the potential of the electrode reached a plateau value of about 1.1 V vs. Ag/Ag+ after 50 s. The cyclic voltammogram of the resulting polymer in 1 M Et4NBF4/acetonitrile is characterized by anodic and cathodic waves at 0.9 and 0.8 V, respectively. The doping level of the polythiophene derivative was found to be equal to about 0.2 which indicates that every five thiophene units carry one positive charge. Cyclic voltammetry results indicates that poly [3-(1-naphthylthiophene)] cannot be n-doped very efficiently in the experimental conditions used in this work.