13C NMR study of the grafting of 13C labeled maleic anhydride onto PE, PP and EPM

Abstract

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.