A nickel alpha-diimine catalyst was used for Grignard metathesis (GRIM) polymerization of 2,5-dibromo 3-hexylthiophene and 2-bromo-5-iodo-3-hexylthiophene monomers. GRIM polymerization of 2-bromo-5-iodo-3-hexylthiophene generated regioregular polymers with molecular weights ranging from 3 000 to 12 000 g . mol(-1). The nickel alpha-diimine catalyst was also successfully used for the GRIM polymerization of a bulky benzodithiophene monomer.