Study of electrolyte effects on electrochemical synthesis and p-doping of poly(thienyl biphenyl) films

The electrochemical synthesis and charging–discharging process of a copolymer consisting of 3-octylthiophene (3-OT) and biphenyl units have been studied in different electrolytic media. The polymer material has been characterized by electrochemical and spectroscopic methods: cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), chronopotentiometry, chronoamperometry and FTIR spectroscopy. The diffusion coefficients of different ions in poly(thienyl biphenyl) (PTB) films have been determined by chronoamperometry and compared with corresponding values in poly(3-octylthiophene) (POT) and poly(paraphenylene) (PPP). The best electrolytic conditions for synthesis of poly(thienyl biphenyl) concerning the copolymer structure was found to be in 0.1 M lithium hexafluoro arsenate (LiAsF6) in acetonitrile. In this electrolyte solution, the content of phenylene segments compared to thienylene segments is highest resulting in a higher degree of cross-linking compared with films made in the presence of the other electrolyte salts studied.