Electrochemistry of conductive polymers 44: A comparative study on electrochemically polymerized polythiophenes from thiophene, bithiophene, and terthiophene

Polythiophenes obtained by electrochemical polymerization of thiophene, 2,2′-bithiophene, 2,2′:5′,2″-terthiophene in 1.0 M LiClO4 propylene carbonate solutions have been studied using various experimental techniques including UV–vis absorption spectroscopic, electrochemical quartz crystal microbalance, and current sensing atomic force microscopic (CS-AFM) experiments. The polythiophene films were obtained by repeated potentiodynamic voltage scans on gold electrodes. Clear differences were observed from the polymer films obtained from the monomers in their electrical, electrochemical, and optical properties due to various factors such as degradation of the polymer at high anodic potentials, conjugation lengths of polymers, incorporated oligomers, and solvated ion pairs in the polymer matrix. The poly(bithiophene) displayed the best conductivity, while the polythiophene showed almost no electrical conductivity.