A series of modified thiophene groups containing PPV-based semiconducting materials, poly[(2,5-bis(octyloxy)-1,4-phenylenevinylene)-alt-(2,2'bithienyleneviny lene)] (PPBT), poly[(2,5-bis(octyloxy)-1,4-phenylenevinylene)-alt-(5,5-thiostilylenevin ylene)] (PPTVT), have been synthesized through a Horner coupling reaction. From the FTIR and H-1 NMR spectroscopy, the configuration of the vinylene groups in the polymers was all trans (E) geometry. The weight-average molecular weights (M-w) of PPBT and PPTVT were found to be 11,700 and 11,800, with polydispersity indices of 2.51 and 2.53, respectively. PPBT and PPTVT thin films exhibit UV-visible absorption maxima at 538 and 558 nm, respectively, and the strong absorption shoulder peaks at 578 and 602 nm, respectively. Solution processed field-effect transistors (FET) fabricated using all the polymers showed p-type OTFT characteristics. The field-effect mobility of the PPTVT was obtained up to 2.3 x 10(-3) cm(2) V-1 S-1, an on/off ratio of 1.0 x 10(5) with ambient air stability. Studies of the atomic force microscopy (AFM) and X-ray diffraction (XRD) analysis of the polymer thin films revealed that all the polymers were amorphous structure. The greater planarity and rigidity of PPTVT compared to PPBT results in elongation of conjugation length and better pi-pi stacking of polymer chains in amorphous region, which leads to improved FET performance. (c) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 111-120, 2009