Effect of non-covalent functionalisation on thermal and mechanical properties of graphene-polymer nanocomposites

Fast growing power densities of modern electronic devices demand high-performance thermal interface materials (TIMs). Owing to the superior thermal conductivity of graphene, composites with graphene fillers dispersed in polymer matrix are expected to be promising TIM candidates. However, the thermal conductivity of graphene-polymer composites is hindered by a high thermal resistance across the interface between graphene fillers and polymer matrix. This research focuses on modulating the thermal transport across the graphene-polymer interface by employing a non-covalent functionalisation technique. Using molecular dynamics simulations, the effects of different non-covalent functional molecules on the graphene-paraffin interfacial thermal resistance are investigated systematically. It is found that the interfacial thermal resistance can be considerably reduced by non-covalent functionalisation and the reduction depends on the coverage of functional molecules. The thermal transport properties of the composites are improved without compromising their mechanical properties. Different functional molecules including 1-pyrenebutyl, 1-pyrenebutyric acid and 1-pyrenebutylamine can produce similar reductions in the interfacial thermal resistance. Based on the effective medium theory, it is demonstrated that the overall thermal conductivity of graphene-paraffin composites increases when the interfacial thermal resistance decreases, which can be achieved by using the non-covalent functionalisation technique.