The electronic absorption and fluorescence spectra, and fluorescence quantum yields (phi(F)) Of Poly(3-methoxythiophene) (PMOT) were determined at room temperature (298 K) in a variety of solvents with different polarities (hexane, cyclohexane, 2-propanol, ethyl acetate, methanol, ethanol, acetonitrile, ethylene glycol, dioxane, propylene carbonate, dimethylformamide, and dimethyl sulfoxide). The solvent effects on the PMOT spectral and photophysical characteristics (absorption and fluorescence wavenumbers) were studied quantitatively, using the Kamlet-Abboud-Taft solvation relationships. The spectral data were used, in combination with the PMOT ground-state dipole moment (mu(g)), to evaluate its first excited singlet-state dipole moment (mu(e)). A mu(e)/mu(g) ratio of 5.8 was obtained by means of the solvatochromic shift method (Bakhshiev＇s and Kawski-Chamma-Viallet＇s correlations). The Kamlet-Abboud-Taft solvatochromic parameters were applied to determine the solute-solvent interactions in the PMOT ground and excited singlet states. (C) 2000 Elsevier Science Ltd. All rights reserved.