Grafting of polyethylene onto graphite oxide sheets: a comparison of two routes

Abstract

Polyethylenes and azide-terminated polyethylenes can be converted to macroradicals and nitrenes, respectively followed by addition reactions onto the unsaturated system of graphite oxide sheets. For the first time, the addition of these macroradicals to graphite oxide sheets was compared by performing grafting reactions at 190 °C in 1,2,4-trichlorobenzene as a solvent and at 100 °C followed by a solvothermal reduction at 150 °C in a solvent mixture of 1,4-dioxane and 1,2-dichlorobenzene. Dispersion of PE coated graphite oxide in a DMF–heptane mixture was utilised to follow the introduction of polyethylene onto the GO sheet surface while the thermogravimetric analysis indicated the extent of this grafting. The grafting ratio was found to be in the 1.5 wt% range and despite this low grafting content, the amount of grafted PE was high enough to dramatically improve the affinity of GO with the heptane phase in the DMF–heptane (50/50 v/v) mixture. Polyethylene functionalised GO was imaged by scanning electron microscopy showing a significant difference in morphology between the two grafting paths. It was found that a higher level of grafting was obtained using a radical grafting reaction in the presence of benzoyl peroxide rather than the thermal cleavage of PE-N₃ onto GO while a similar grafting content was obtained with the thermal cleavage of PE-N₃ onto GO grafted trimethoxy(7-octen-1-yl)silane.