Interactions between highly isotactic acrylonitrile homopolymers and alkalis in dimethyl sulfoxide solvent were examined. Coloration occurred as soon as polyacrylonitrile was added to a dimethyl sulfoxide/alkali mixture. The effects of alkali on highly isotactic polyacrylonitrile were greater than those on ordinary polyacrylonitrile. The intrinsic viscosity of polyacrylonitrile decreased quickly with the addition of sodium ethoxide and sodium hydroxide, and the effect of sodium ethoxide was more prominent than that of sodium hydroxide. As the concentration of sodium ethoxide and sodium hydroxide went beyond 0.01 mol/L, the intrinsic viscosity showed a trend of increasing. Within the first half-hour, there was a great drop in the intrinsic viscosity of highly isotactic polyacrylonitrile, and then the intrinsic viscosity appeared to increase. The intrinsic viscosity of highly isotactic polyacrylonitrile increased continuously with the addition of diethylamine along with time. The effects of alkalis on the tacticity of the polymers followed the order of the alkali strength. Diethylamine was more effective for moderating the stabilization exotherm of polyacrylonitrile than sodium ethoxide and sodium hydroxide. (c) 2006 Wiley Periodicals, Inc.