The reaction products from the radically initiated grafting of specifically 13 C-enriched maleic anhydride ([2,3-13 C2]MA) onto polyethene, isotactic polypropene and ethene-propene copolymers in the melt and in solution are investigated using noise-decoupled and 1D inadequate 13 C NMR spectroscopy. The sites of attachment and the structures of the grafts depend on (co)polymer composition. In random EPM, MA attaches to methylene and methine carbons in the backbone. In alternating EPM, MA attaches solely to polymer methines, indicating that (CH2)m sequences with m > 3 are needed for MA attachment to backbone methylene carbons. In the copolymers and in IPP, grafts are single succinic anhydride rings; in HDPE and LDPE short MA oligomers are also present. In polyolefins containing polypropene sequences, chain scission can yield structures in which the anhydride ring is attached to the chain terminus via a fully substituted double bond.

The chemical structure of polyolefins grafted with maleic anhydride (MA) has been the subject of much speculation, but thorough experimental studies are rare. MA with 99% 13C in the double bond was synthesized and grafted onto PE, EPM and PP in the melt and solution. 1D INADEQUATE 13C NMR spectroscopy was used to characterize the products. Saturated, monomeric MA graft structures are formed. Only for grafted PE short MA oligomers are demonstrated. Grafting occurs on secondary and tertiary carbons depending on the composition of the polyolefin. For PP a new, unsaturated MA graft structure on the polymer chain terminus is identified. All graft structures are rationalized using a simple grafting mechanism.