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 C-13-, H-1- 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. (c) 2006 Society of Chemical Industry.