Synthesis of end-capped regioregular poly(3-hexylthiophene)s via direct arylation.

The synthesis of regioregular head-to-tail poly(3-hexylthiophene)s capped with aryl groups (Ar-HT-P3HTs) has been accomplished by palladium-catalyzed polycondensation of 2-bromo-3-hexylthiophene (1) via direct arylation. A variety of aryl groups are installed at the initiated end in 86%-98% selectivity using aryl bromides and iodides as capping agents. The polymerization proceeds via a two-stage process. Before monomer 1 is consumed, the competitive formation of end-capped and non-capped HT-P3HTs is operative, where the molecular weight increases linearly with monomer conversion. After 1 is consumed, the resulting polymers are coupled with each other to afford highly end-capped HT-P3HTs.