The copolymers of 2-methoxy-5-2'-ethyl-hexyloxy-1,4-phenylenevinylene (MEH-PV) and 2,3-diphenyl-5-octyl-1,4-phenylenevinylene were prepared via the Gilch route with their chain compositions and the reactivity ratios of the monomers estimated by H-1 NMR spectroscopy. The results indicated that the copolymers tended to form an alternative copolymer as the feed ratio of the monomers closed to one-half. When an individual copolymer solution in tetrahydrofuran was spun-cast to form a film, the MEH-PV units were able to attract the like units from the adjacent chains. As a result, the ultraviolet-visible absorption spectrum of the alternative copolymer in film form was broader than the spectra of those with different compositions. The photoluminescence spectra of the copolymers in film form exhibited the characteristic shoulder of poly(2-methoxy-5-2'-ethyl-hexyloxy-1,4-phenylenevinylene), even though the content of MEH-PV units was not great enough for the formation of repeat units in sequence. (C) 2003 Wiley Periodicals, Inc.