NiCl2 (bpy)-catalyzed polycondensation between p-dibromobenzene and m-dibromobenzene was carried out under various conditions. With the polycondensation, a series of copolymers with number-average molecular weights of 2400 (by gel permeation chromatography with polystyrene standards) was formed, and some samples had good solubility in organic solvents. The IR spectra and the ultraviolet spectra measured in a tetrahydrofuran (THF) solution of the copolymer showed that there were p-phenylene and m-phenylene units in the copolymer. According to analyses with differential scanning calorimetry, thermogravimetric analysis, and X-rays, with an increasing molar ratio of m-phenyl units in the copolymer, the glass-transition temperature, the temperature of viscous flow, and the crystallizability of the polyphenylene copolymer decreased. The fluorescence spectra of the copolymer measured in a THF solution showed an emission maximum at 373-376 nm, whereas the maximum shifted to 436.6 nm for the film. (C) 2003 Wiley Periodicals, Inc.