Microstructure of Maleic Anhydride Grafted Polyethylene by High-Resolution Solution-State NMR and FTIR Spectroscopy

The microstructure of maleic anhydride (MA) grafted polyethylene (PE), MA- g -PE, has been successfully characterized by high-resolution NMR and FT-IR spectroscopy. The carbonyl asymmetric and symmetric stretchings of MA- g -PE exhibit lower shifts with an increase in the grafting degree of MA, suggesting stronger inductive interactions between different grafts in a solid state. The 1 H and 13 C NMR spectroscopy of [2,3- 13 C 2 ]MA grafted PE with a low molecular weight (lmPE), [2,3- 13 C 2 ]MA- g -lmPE, demonstrates that [2,3- 13 C 2 ]MA- g -lmPE contains fewer succinic anhydride (SA) oligomeric grafts with a terminal unsaturated MA ring (oligo-MA) in addition to more SA oligomeric grafts terminated with a saturated SA ring (oligo-SA), the only structure that had been observed prior to this study. The formation of oligo-MA and oligo-SA can be explained by a mechanism based on two different termination processes: disproportionation between a grafting radical and a macroradical on a secondary carbon in lmPE or another grafting radical as well as hydrogen abstraction of a grafting radical from a secondary carbon on lmPE.