A series of copolymers containing 1,4-phenylenevinylene (PV) and either 2-n-butoxy-5-methoxy-1,4-phenylenevinylene (BMPV) or 2-n-dodecyloxy-5-methoxy-1,4-phenylenevinylene (DDMPV) units were prepared in the form of thin films from their water-soluble sulfonium-salt precursor polymers. The electrical conductivity of the I2- and FeCl3-doped copolymers exhibits a steep initial increase with an increase in the content of the BMPV or DDMPV units, followed by a slower increase to finally reach the values of that of the corresponding homopolymers, PBMPV and PDDMPV, respectively. The conductivities of the I2- and FeCl3-doped, drawn BMPV copolymer films ranged from 35 to 266 S cm-1, and from 10(-1) to 256 S cm-1, respectively, depending on the composition. PDDMPV films could be uniaxially drawn at 150-160-degrees-C to a draw ratio of 5, and gave an electrical conductivity value of 27 S cm-1 when doped with I2, whereas I2-doped PDDMPV films, obtained from the precursor polymer that itself had been pre-drawn to the draw ratio of 5, exhibited a conductivity of 46 S cm-1. PDDMPV was found to be soluble in p-xylene, but PBMPV was insoluble in this solvent. The presence of the long dodecyloxy group enables the precursor polymer of PDDMPV to form an ordered structure. The u.v.-vis. spectra of the dialkoxy substituted homopolymers and their corresponding copolymers were red-shifted relative to the parent PPV, suggesting a decreased bandgap, which was consistent with the electron-donating nature of the alkoxy substituents. In general, the electrical conductivities of the DDMPV copolymers were lower than those of the BMPV copolymers, which can be ascribed to the presence of longer insulating alkoxy groups in the former.