Electrochemical behavior of poly(3-hexylthiophene). Controlling factors of electric current in electrochemical oxidation of poly(3-hexylthiophene)s in a solution

Electrochemical response of regio-random and regio-controlled poly(3-hexylthiophene), P3HexTh, was investigated by cyclic voltammetry. P3HexTh underwent electrochemical oxidation at about 0.4 V vs. Ag+/Ag in a THF solution, and the peak anode electric current, ipa, was proportional to the sweeping rate v; ipa=const×v1/2. These data indicated that diffusion of the P3HexTh molecule in the solution was important to determine ipa. Application of a Matsudaʹs equation with assumptions gave a diffusion coefficient, D, of about 1×10−7 cm2 s−1 at molecular weight of about 5000, and the D value steeply decreased with increase in the molecular weight.