Covalent polymer functionalization of graphene nanosheets and mechanical properties of composites

TLDR

Dispersing graphene nanosheets in polymers and controlling their interfaces is difficult due to strong interlayer cohesion and surface inertia. The study presents an efficient method to functionalize graphene nanosheets. Covalent attachment of diazonium initiators followed by atom‑transfer radical polymerization grafts polystyrene chains onto the graphene surface with 82 wt % efficiency. The grafted nanocomposites exhibit a 15 °C rise in polystyrene glass‑transition temperature and, at 0.9 wt % loading, show ~70 % higher tensile strength and ~57 % higher Young’s modulus, indicating improved processing and interfacial properties.

Abstract

For developing high performance graphene-based nanocomposites, dispersal of graphene nanosheets in polymer hosts and precise interface control are challenging due to their strong interlayer cohesive energy and surface inertia. Here we report an efficient method to functionalize graphene nanosheets. The initiator molecules were covalently bonded to the graphene surface via a diazonium addition and the succeeding atom transfer radical polymerization linked polystyrene chains (82 wt% grafting efficiency) to the graphene nanosheets. The prominent confinement effect arising from nanosheets resulted in a 15 °C increase in the glass transition temperature of polystyrene compared to the pure polymer. The resulting polystyrene nanocomposites with 0.9 wt% graphene nanosheets revealed around 70% and 57% increases in tensile strength and Young's modulus. The protocol is believed to offer possibilities for optimizing the processing properties and interface structure of graphene-polymer nanocomposites.