Kinetics and mechanism of polynierization of polythiophene by FECL3 in chloroform and acetonitrile

Summary form only given. We report on the kinetics of polymerization of thiophene (T) with FeC13 either in suspension in chloroform or in acetonitrile solution. The rate of polymerization was followed by gas chromatography and by calorimetry. The reaction of FeC13 with 2-methyl thiophene was also followed in both solvents as a model reaction using calorimetry and UV/Vis spectroscopy. The results in chloroform are in agreement with the hypothesis of reaction involving the FeC13 ciystal surface. The reaction is quantitative for FeCl3/T ratio higher than 2. At low monomer concentration (< 0. I M) the polymerization follows a first order versus monomer and the polymerization rate is proportional to the FeC13 surface. For higher monomer concentration the apparent first order rate decreases when the monomer concentration increases. The results are analyzed in term of monomer diffusion through a polymer layer. The inhibiting influence of ethanol which is present in non purified chloroform is explained in term of solubilization of inert FeCl3, ethanol complex. The polymerization takes place also in homogeneous solution of FeCl3 in acetonitrile showing that the presence of FeCl3 crystals is not necessary in contradiction with recent reports. The reaction is quantitative for monomer concentration up to 0.05 M (FeCl3=0.7 M) but a maximum T concentration of 0.07 M can polymerized in those conditions. This is correlated with the formation of a complex (2 methyl T, 6 FeCl3 ) observed by spectroscopy in the same solvent. These data are used for an analysis of the mechanism of formation of, previously reported, block copolymers with PT sequences.