Cysteamine functionalised reduced graphene oxide modification of maleated poly(propylene)

Abstract

Graphene oxide (GO) was reduced (rGO) and then functionalised with an amino terminated thiol molecule (cysteamine) via a thiol-ene click chemistry reaction to produce reduced graphene oxide-cysteamine (rGO-cyst). The presence of the C–S bond in the X-ray photoelectron spectrum (XPS) confirmed the reaction between the thiol in cysteamine and both the double bonds present on the rGO surface and the pyrazolic structures formed due to reduction. The rGO-cysyteamine was reacted with polypropylene-graft-maleic anhydride (PP-g-MA) to produce PP-g-MA-rGO-cysteamine, where the free amino group present on the rGO-cysteamine reacts with the maleic anhydride group of PP-g-MA. This was confirmed from solid state 13C Magic-Angle-Spinning, Nuclear Magnetic Resonance (MAS NMR), Fourier transform infrared (FTIR) and XPS studies which demonstrated that a mixture of open and closed ring structures based on amides, imides and imines were formed. Growth of the PP chain on the rGO surface was observed from electron microscopy imaging. Cysteamine acts like a ‘cross-linker’ between the rGO and PP-g-MA, increasing interfacial interaction between the two phases resulting in increased thermal stability and altering the crystallization behaviour of the maleated PP. The approach described could be used to compatabilise graphene oxide and a range of polymers to produce functional composite materials.