Extremely regio‐regular poly (3‐alkylthiophene)s from simplified chain‐growth Grignard metathesis polymerisations and the modification of their chain‐ends

A simplified route to regio‐regular poly(3‐alkylthiophene)s (P3AT) with predetermined molecular weights and low molecular weight distributions based on the chain‐growth GRIM polymerisation of 2,5‐dibromo‐3‐alkylthiophenes is detailed. It is proposed by way of in‐depth 13C‐, 1H‐ and two‐dimensional NMR characterisations that the resulting P3ATs are quasi‐100% regio‐regular except for one regio‐irregular pair at one chain‐end. It is probable that chain‐end groups exhibit reduced conjugation with the rest of the polymer. A comparison of the preparation of poly(3‐hexylthiophene) and poly(3‐butylthiophene) (P3BT) is presented. New methods required for the hydrogenation, formylation and bromomethylation of the chain‐ends of P3BT, necessary to overcome its poor solubility and low reactivity, are described.