Electrochemical doping of polybutylthiophene and polydibutylbithiophene - in situ EPR and conductivity studies

The electrochemical spin response in poly(3-butylthiophene) and poly(4,4’-dibutyl 2,2’-bithiophene) was studied by in situ joint EPR - cyclic voltammetry experiments. Both polymers although having the same stoichiometry differ in the distribution pattern of the alkyl groups along the polymer chain. In poly(4,4'-dibutyl-2,2'-bithiophene) spin creation and anihilation occur at more positive potentials and within much narrower potential range as compared to poly(3- butylthiophene). This last property may imply better stereoregularity of the former. In both polymers the majority of charges introduced during oxidative doping are stored in a form of bipolarons similarly as in other compounds from the polythiophene family. In situ studies have shown that the conductivity increases steadily during the oxidation even if the potential of the reversible oxidation is exceeded. However overoxidation results in a significant decrease of electroactivity of the sample in consecutive cycles