Critical parameters for product quality and yield in the polymerisation of 3,3″-didodecyl-2,2′:5′,2″-terthiophene

The yield and molecular weight of CHCl3 soluble poly(3,3″-didodecyl-2,2′:5′,2″-terthiophene) in the presence of FeCl3 were shown to depend strongly on quality and addition rate of the reagents, and on temperature. Best results were obtained by further drying commercial anhydrous FeCl3 and by slow addition of the reagents. Under these conditions the product molecular weight (Mw) and the yield of the CHCl3 soluble polymer were, respectively, 23 000–25 000 Da and 38–66%, and no insoluble polymer residue was obtained. Using raw commercial FeCl3 and/or adding the reagents all at once gave significant amounts of insoluble polymer fraction. Comparison with literature runs confirms that the polymerisation at 40 °C yields higher molecular weight product than at room temperature, and no insoluble polymer was still formed, provided that the above optimum reagents parameters were used.