Thiophene-based block copolymers are synthesized by addition of bromothiophene and the Knochel-Hauser base (TMPMgCl center dot LiCl). Nickel-catalyzed deprotonative C-H coupling polycondensation of 3-substituted-thiophenes proceeds to give head-to-tail-type poly(3-substituted thiophen-2,5-diyl) bearing nickel at the polymer end. Block copolymers of thiophene derivatives are obtained by successive addition of 2-bromo-3-alkylthiophene and magnesium amide to a living polythiophene end. The use of nickel catalyst bearing an o-tolyl group gives the tolyl-group-terminated thiophene diblock copolymers in high efficiency. Triblock copolymer is also synthesized by the iterative addition of bromothiophene and TMPMgCl.LiCl.