This article reports the synthesis and characterization of a new polythiophene derivative phenoxy-substituted, the poly[3-(4-octylphenoxy)thiophene] (POPOT). The oxidative polymerization was found to yield low molecular weight material, whereas a modified Grignard metathesis (GRIM) yielded polymers of high molecular weights. One- and two-dimensional NMR indicated the latter to be highly regioregular. POPOTs exhibited higher thermal stabilities than equivalent alkoxy-substituted polythiophenes and exhibited red shifts in the absorption spectra with respect to equivalent. The absorption spectra showed a red shifted lambda(max) at 540 nm in tetrahydrofaran solutions and 580 run in spin-coated films, with respect to poly(3-alkylthiophene)s. A further red shift of 40 nm in going from solution (540 nm) to solid states (580 nm) is correlated with results from density functional theory electronic structure calculations. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7505-7516, 2008