A long alkylsilyl group was attached to a thiophene ring system to overcome the instability of 2.5 bis(halomethyl) thiophene monomers, by imparting steric hindrance and electronic delocalization. The resulting stable monomer could be used directly to prepare low band gap poly(thienylenevinylene) (1.57 eV) through heteroaromatic dehydrohalogenation polymerization.