Polymerization of acrylonitrile catalysed by the tri-isobutylaluminium-chromium acetylacetonate-pyridine system

The system chromium acetylacetonate (I)-tri-isobutylaluminium (II)-pyridine (III) induces polymerization of acrylonitrile if the components are added in the strict order: I and II, then III and finally AN. It is shown that pyridine prevents the deactivation of the catalyst caused by the monomer. It was found that the mechanism of polymerization is anionic. A general reaction scheme is proposed and equations are derived describing the kinetics of the process and the variation in the molecular weight of the PAN during the course of polymerization.