Asymmetric 2,5-dibromo-3,4-phenylenedioxythiophenes having a branched alkyl side chain at the phenylene part are polymerized by Yamamoto (Y) and Grignard metathesis (GRIM) methods to give several soluble poly(3,4-phenylenedioxythiophene)s. Poly{1,4[4-(2-hexylundecyl) phenylene]dioxythiophene-2,5-diyl) synthesized by GRIM (PPTa-G) exhibits a narrower band gap about 1.85 eV, higher absorption coefficient, and shorter pi-stacking distance about 3.9 A than those of the polymer synthesized by Y method (PPTa-Y). Introducing a fluorine substituent at the phenylene part of PPTa-Y deepens the energy level of a highest occupied molecular orbital of the polymer 0.17 eV. Thin film of PPTa-G shows hole mobility of 2.52 x 10(-3) cm(2) V-1 s(-1) determined by performance of the organic field-effect transistor in a preliminary experiment. (C) 2015 Elsevier B.V. All rights reserved.