PMMA-grafted graphene nanoplatelets to reinforce the mechanical and thermal properties of PMMA composites

In order to realise the potential of graphene nanocomposites it is vital to control the degree of dispersion and achieve a strong graphene polymer interface. Herein, we developed a facile grafting to functionalisation approach for graphene nanoplatelets. NH2-terminated graphene nanoplatelets, NH2 GNPs, prepared by a diazonium coupling were used as a platform to covalently graft PMMA chains to the surface of graphene through an amidation between the NH2 groups and PMMA chains, PMMA NH GNPs. A degree of PMMA grafting of 3.8 wt, one chain per 40 carbon atoms, was found to both improve the dispersion of the GNPs in a PMMA matrix and give strong graphene-polymer interfaces compared to as-provided GNPs. Thus, 2 wt of PMMA NH GNPs in PMMA was found to increase the elastic modulus, strength and strain at break of PMMA, whereas the incorporation of unmodified GNPs showed poor levels of reinforcement at all loadings. Furthermore, Tg and Td of PMMA were increased by 15 C and 29 C, respectively, by adding 5 wt of PMMA NH GNPs, whereas incorporating unmodified GNPs led to smaller increases. This work offers the possibility of controlling the properties of graphene-polymer composites through chemically tuning the graphene-polymer interface, which will have broad implications in the field of nanocomposites.