Acrylonitrile was polymerized by aa\u27-azobisisobutyronitrile (AIBN) as an initiator at 50℃ in liquid sulfur dioxide mixed with an added solvent. The added solvents were cyclohexane, benzene, toluene, p-xylene, ethylbenzene, isopropylbenzene, p-cymene, chlorobenzene, benzonitrile and ethyl benozate, respectivelv. In each case, only poly-acrylonitrile was obtained and the formation of the polymer was independent on the solvent added. No acrylonitrile polysulfone was found in the reaction mixture. The added solvents showed no appreciable influence on the overall rate of polymerization (Rp) in the range of the experimental condition
