Regioregular poly(3-substituted thiophene) derivative bearing pentamethyldisiloxane moiety at the 3-substituent is prepared by nickel-catalyzed polymerization reactions with dehydrobrominative or debrominative generation of the organometallic monomer. The monomer precursors 2-bromo-3-(4pentamethyldisiloxybutan-l-yl)thiophene (1a) and 2,5-dibromo-3-(4-pentamethyldisiloxybutan-l-yl)thiophene (1b) are prepared from 3-methylthiophene with 4-5 steps in overall good yields. Treatment of 1a with TMPMgCl center dot LiCl at room temperature for 3 h forms an organometallic monomer and following the addition of a nickel catalyst affords the corresponding polythiophene bearing a disiloxane moiety in the side chain. The reaction of 1b with Grignard reagent leads to the similar monomer and addition of a catalytic amount of [NiCl2(dppe)] also affords polythiophene in highly regioregular manners. The obtained polythiophene is found to be dissolved in a hydrocarbon such as hexane.