On the nature of the active centres in the anionic polymerization of methacrylonitrile—II. Initiation with organomagnesium compounds

It is shown by i.r. spectroscopy that the anionic polymerization of methacrylonitrile using organomagnesium compounds as initiators leads to two types of “living” ends i.e.

and

The active centres form complexes with the monomer, as well as with the nitrile groups of the monomer units in the polymer chain, in a hydrocarbon medium. The complexes are characterized by bands in the 2250–2280 cm^?1 region. Addition of donors destroys the complexes and in some cases (hexamethylphosphorous triamide) converts the complex of organomagnesium compound with monomer into a “living” end. In ethers as solvent, the dominant side-reaction is addition of the initiator to the nitrile group of the monomer.