In this report, four donor-acceptor copolymers, P(NDT3-BT), P(NDT3-BO), P(NDF3-BT), and P(NDF3-BO), using 5,10-didodecyl-naphtho[1,2-b:5,6-b]dithiophene (NDT3) or 5,10-didodecyl-naphtho[1,2-b:5,6-b]difuran (NDF3) as an electron-rich unit and benzodiathiazole (BT) or benzoxadiazole (BO) as an electron-deficient one, were designed, synthesized, and characterized. Detailed systematical investigation was developed for studying the effect of the S/O atoms on the optical, electrochemical, and morphological properties of the polymers, as well as the subsequent performance of the organic field-effect transistors (OFETs) fabricated from these copolymers. It was found that, compared with NDF3-based P(NDF3-BT)/P(NDF3-BO), by replacing NDF3 with stronger aromatic NDT3, the resultant P(NDT3-BT)/P(NDT3-BO) show smaller lamellar distance with an increased surface roughness in solid state, and relatively higher hole mobilities are obtained. The hole mobilities of the four polymers based on OFETs varied from 0.20 to 0.32 cm(2)V(-1)s(-1) depending on their molecular structures, giving some valuable insights for the further design and development of a new generation of semiconducting materials. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2465-2476