Low potential electrochemical polymerization of 3-chlorothiophene in mixedelectrolytes of boron trifluoride diethyl etherate and trifluoroacetic acid

Poly(3-chlorothiophene) (PCT) films were synthesized electrochemically by d irect oxidation of 3-chlorothiophene (CT) in mixed electrolytes of boron tr ifluoride diethyl etherate (BFEE) and trifluroacetic acid (TFA). The oxidat ion potential of 3-chlorothiophene in pure BFEE was measured to be only 1.5 4 V versus SCE. This value is much lower than that determined in neutral me dium (2.18 V vs. SCE). The addition of TFA to BFEE can further decrease the oxidation potential of the monomer. The oxidation potential of CT in the m ixed electrolyte of BFEE containing 30% TFA (by volume) was found to be as low as 1.16 V (vs. SCE). PCT films with the highest quality were obtained f rom the media of BFEE + 10-15% TFA and they were characterized to have abou t 24-32 repeat units. The doping level and conductivity of PCT films also i ncreased significantly by using the mixed electrolytes. (C) 2001 Elsevier S cience B.V. All rights reserved.