Polythiophenes bearing a siloxane moiety in a substituent at the 3-position are prepared by deprotonative polycondensation of 2-bromo-3-substituted-thiophene with a bulky magnesium amide chloromagnesium 2,2,6,6-tetramethyl-piperidine-1-yl lithium chloride salt (TMPMgCl center dot LiCl) catalyzed by a nickel complex. Deprotonation takes place at 60 degrees C for 1 h to form the corresponding thiophene magnesium species, which is subjected to the polymerization by addition of 0.1-5 mol % NiCl2(PPh3)IPr (IPr: 1,3-bis(2,6-diisopropylphenyl)imidazole-2-yl). Polymerization proceeds in a highly regioregular manner, and the molecular weight of the thus-obtained polymer is controllable by the ratio of monomer feed/catalyst loading to indicate M-n of up to 280 000 with narrow molecular weight distribution. Chlorothiophenes are also found to induce polymerization in a deprotonative manner with TMPMgCl"LiC1 or nBuLi (the Murahashi coupling polymerization). The obtained polymers bearing a siloxane moiety in the substituent is revealed to be dissolved in a hydrocarbon allowing formation of thin film from hexane.