We have studied the linear and nonlinear optical properties of model oligomers based on trans,trans'-distyrylbenzene to investigate the effects of chemical modification on the electronic structure of stilbenoid oligomers and polymers. Replacing the central para-phenylene ring with a meta-phenylene ring reduces the conjugation of the molecule and introduces disorder into the film, which significantly reduces Davydov splitting of the main absorption band. Alkoxy substitution of any of the phenylene rings red shifts the lowest energy absorption band and enhances the oscillator strength of a high-energy sideband. Absorption by aggregates, which is obscured by effects of scattering on the absorption spectrum, is clearly revealed by electroabsorption spectroscopy. (C) 2000 Published by Elsevier Science B.V.