Oxidative copolymerization of 8-aminoquinoline (AQ) and o-anisidine (AS) using ammonium persulfate as oxidant was studied under various polymerization conditions and fine and uniform copolymer particles of several micrometers, determined by laser particle size and atomic force microscopic analyses, were synthesized simply. The polymerization yield, molecular weight, solubility, electroconductivity, and thermostability of the copolymers were systematically studied by changing the comonomer ratio, polymerization temperature, monomer/oxidant ratio, and acidic medium. Single chain configuration of the copolymers with various AQ/AS ratios was simulated and well related to the intrinsic viscosity. The macromolecular structure of the resulting copolymers was wholly characterized by elementary analysis, IR, UV-vis, high-resolution H-1 NMR, and solid-state high-resolution C-13 NMR. The results show that the oxidative copolymerization of AQ and AS is exothermic. All copolymers are totally soluble in H2SO4, HCOOH, m-cresol but their solubility in other solvents depends significantly on the comonomer ratio, and also on the polymerization conditions. The oxidative polymer obtained is a real copolymer containing AQ and AS units rather than a mixture of two homopolymers. The AQ content calculated based on the H-1 NMR spectra of the copolymers is slightly higher than feed AQ content when feed AQ content is lower than 70 mol%. However, the AQ content calculated based on the 1 3 C NMR and elementary analyses is lower than the feed AQ content when the AQ feed content is higher than 50 mol%. A peculiar dependency of molecular weight and electroconductivity of the copolymers on the AQ/AS ratio was observed. The decomposition temperature of the copolymers rises with increasing AQ content. Therefore, the thermostability of the copolymers increases with increasing AQ content due to its high aromaticity. (C) 2004 Elsevier Ltd. All rights reserved.