Über den mechanismus der anionischen polymerisation von acrylnitril mit triäthylphosphin, 8. Über makrozwitterionen

The anionic polymerization of acrylonitrile with triethylphosphine as initiator in dimethylformamide was studied at different temperatures and various monomer/initiator ratios. ¹H-NMR spectroscopy and gel permeation chromatography as well as emission spectra analysis of phosphorus were employed on both the crude polymer and the polymer samples obtained by reprecipitation and by gel permeation chromatography. In addition, the number of polymer anions was determined by spectroscopic end group analysis. Thus, it was possible to show the occurrence of a polymerization via macrozwitterions besides the dominant transfer mechanism and also the necessity of minimum values of the polymerization temperature as well as the monomer/initiator ratio for the formation of macrozwitterions, . If these conditions are not realized, a transfer reaction to the monomer through proton abstraction takes place by means of the zwitterion , which is formed by the interaction of triethylphosphine and acrylonitrile, and the resulting anion, , initiates the polymerization chain. As a result ofthe increase ofthe initiator concentration as well as that of the temperature, more side-reactions in the polymerization occur, as can be noted by IR- or UV-spectroscopical analysis of the polymer.