New semiconducting polymer, poly[1,4-bis(($E$)-2-(5-bromo-3-dodecylthiophen-2-yl)vinyl)benzene], was designed, synthesized and characterized. The structure of polymer was confirmed by $^1H$-NMR, IR and elemental analysis. The polymer was soluble in specific organic solvent. The weight-average molecular weights (MW) of polymer was found to be 11,000 with polydispersity of 1.82. UV-Visible absorption spectrum showed the maximum absorption at 428 nm (in solution) and 438 nm (in film). The highest occupied molecular orbital (HOMO) energy of the polymer is -5.36 eV by measuring cyclic voltammetry (CV). A solutionprocessed polymer thin film transistor device shows a mobility of $8.59{pm}10^{-4};cm^2;V^{-1};s^{-1}$, an on/off current ratio of $2.0{ imes}10^4$.