Synthesis of poly(3-hexylthiophene) with a persity narrower polydispersity

The polymerization of 2-bromo-3-hexyl-5-iodothiophene (1) with isopropylmagnesium chloride and Ni(dppp)Cl-2 was quenched with 5 M hydrochloric acid instead of water to yield head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a very low polydispersity. The (M) over bar (n) of the polymer was controlled by the feed ratio of 1 to Ni(dppp)Cl2. Quenching with 5 M hydrochloric acid seemed to promote protonolysis of HT-P3HT-Ni complexes before the coupling reaction between HT-P3HT.