Structural Analysis of Poly(3-hexylthiophene) Prepared via Direct Heteroarylation Polymerization

This study reports the synthesis and characterization of poly(3-hexylthiophene) (P3HT) from a direct heteroarylation polymerization of two isomeric monomers, 2-bromo-3-hexylthiophene (monomer 1) and 2-bromo-4-hexylthiophene (monomer 2). Using the Herrmann-Beller catalyst along with P(o-NMe2Ph)(3), the resulting polymers are obtained in excellent yields and exhibit a good number-average molecular weight (M-n of 33 and 16 kDa, respectively). Detailed H-1 NMR analyses reveal less than 1% of homocouplings and no evidence of beta-branching. Dehalogenation is identified as the main chain termination step and preferentially occurs on monomer 2. The melting temperature (237 degrees C) and hole mobility (up to 0.19 cm(2) V-1. s(-1)) of the nearly defect-free P3HT obtained from this simple polymerization of monomer 1 are comparable, if not superior, to those obtained with commercially available GRIM and Rieke samples.