Effect of molar ratio of oxidizer/3-hexylthiophene monomer in chemical oxidative polymerization of poly(3-hexylthiophene)

Poly(3-hexylthiophene) (P3HT) was successfully prepared by oxidative polymerization of 3-hexylthiophene (3HT) using FeCI3 in various solvents, including hexane, nitrobenzene, and acetonitrile. The range of molar ratios between the oxidant and monomer used in the reactions was 1:1-1:10. A similar result was obtained when the polymerization was conducted in ethanol-free chloroform, which indicated that the Lewis acidity of anhydrous FeCl3 was significantly affected by even a small amount of ethanol. The yield of P3HT obtained in the above solvents was proportional to the monomer/FeCl3 molar ratio, and the yield in hexane was the highest among all solvents. Analysis of the methanol extract of P3HT using Surface-Assisted Laser Desorption/Ionization Time-Of-Light Mass Spectrometry (SALDI TOF MS) showed that the 3HT dimer was formed at the initial stage of polymerization. The structure of the oligomer was also analyzed using SALDI TOF MS and H-1 NMR. These results provide detailed insights into the polymerization mechanism of 3HT with FeCl3 as oxidant. (C) 2017 Elsevier B.V. All rights reserved.