Initiation of anionic polymerization of acrylonitrile with tertiary amines and ethylene or propylene oxide: some mechanistic aspects

The results of the study of the mechanisms of the initiation reactions of anionic polymerization of acrylonitrile under the action of a new initiating system with tertiary amine-ethylene (or propylene) oxide are presented. H-1 NMR spectroscopy it was shown that, ethylene oxide slowly and in equilibrium reacts with 1,4-diazabicyclo[2.2.2] octane at room temperature with the formation of zwitterions, which initiate the further polymerization of ethylene oxide. In the presence of acrylonitrile, zwitterions quickly join it causing rapid growth of polyacrylonitrile chains on the formed carbanions. The reaction scheme for the initiation is suggested. The scheme was confirmed by quantum-chemical calculations of thermodynamic parameters for the reversible reactions of addition of ethylene (or propylene) oxide to some tertiary amines with the formation of zwitterions. The relationship between the molecular structure of tertiary amines and their ability to form zwitterions is discussed.