A STUDY BY N-15-NMR OF END-GROUPS FORMED FROM AZOBISISOBUTYRONITRILE

Azobisisobutyronitrile, enriched with N-15 in its nitrile groups, was used to initiate polymerizations at 60 degrees C of styrene, methyl me thacrylate and vinyl acetate and also copolymerizations of styrene wit h methyl methacrylate. The resulting polymers were examined by high-fi eld N-15-NMR spectroscopy. The chemical shift for the enriched site in a Me(2)C(CN)- end-group depended upon the nature of more remote units . There was only limited evidence for effects of the stereochemistry o f monomeric units near the end-groups.