Regioregular poly(3-hexylthiophene) (P3HT) has been a commonly used p-type semiconducting material for solution processable organic electronics. To establish a living system of "Negishi-type catalyst-transfer polycondensation (NCTP)" using zincate complex as a synthetic method for well-defined P3HT having predictable molecular weight (MW) and low dispersity (-D), the ligands of Ni catalyst were optimized. As a result, a ligand of 1,2-bis(dicyclohexylphosphino) ethane produced P3HTs with highly controlled number average MWs (1650-32,800) and very low -D values (1.03-1.17). The polymerization results were strongly influenced by steric hindrance based on the factors of cone angle and bite angle of Ni catalysts, and/or electron-donating ability of phosphine ligands. In addition, we succeeded in the two-stage polymerization of P3HT and the synthesis of P3HT-b-poly(3-octadecylthiophene), the latter of which is the first demonstration by NCTP using zincate complex. (c) 2014 Wiley Periodicals, Inc.