Acrylonitrile (AN) was copolymerized with acrylic acid (AA), methacrylic acid (MAA), and itaconic acid (IA) by the aqueous suspension method at 40°C with ammonium persulfate and sodium metabisulfite as the redox initiator. The reactivity ratios for the AN–AA and AN–IA systems were also calculated by the Finemann–Ross and the Kelen–Tüdõs methods. Higher r2 (AA) for the AN–AA system in comparison to r2 (IA) for the AN–IA system indicates greater reactivity of AA toward the propagating species. The influence of co-monomers on intrinsic viscosity, tacticity, and number-average sequence lengths was studied. 13C-NMR spectra revealed that AN copolymers having approximately 2 mol % of AA have a greater percentage (>30%) of isotactic content than of homopolyacrylonitrile. Tacticity has also been calculated from infrared spectra of the polymers using stereospecific absorption bands at 1250 and 1230 cm−1. © 1993 John Wiley & Sons, Inc.