Role of the aspect ratio of graphene oxide (GO) on the interface and mechanical properties of vitrimer/GO nanocomposites

Epoxy vitrimers are raising an increasing interest for the formulation of multifunctional nanocomposites due to their reversible covalently crosslinked network capable of self-arranging upon stimulation without losing integrity, providing them with new properties such as self-healing or shape memory. The incorporation of functionalized nanomaterials to epoxy vitrimers can further improve and promote those functions, due to the formation of strong reversible vitrimer/nanofiller interfaces. Herein, how the addition of graphene oxide (GO) flakes with different aspect ratios affects such interface, hence the properties, of vitrimer/GO nanocomposites was investigated and compared to those rendered by their epoxy analogues. An evaluation of the nature of the GO/polymers interface performed by Raman spectroscopy confirmed the existence of stronger interfaces between both GOs and the vitrimer relative to the epoxy, which led to better dispersions of the flakes and enhanced mechanical properties, independently of the flakes aspect ratio. Thicker GO flakes were found, however, to render stronger interfaces, hence better mechanical properties, than thinner flakes with higher aspect ratio. The stress-relaxation behaviour of both matrices was found to improve by adding GO materials as fillers, with this result being more pronounced for the vitrimer systems and independent on the aspect ratio of the GO flakes. These findings suggest not only that vitrimer/GO nanocomposites can lead to improved mechanical and stress-relaxation properties relative to their epoxy analogues, but also that selecting a GO with a specific aspect ratio allows the design of nanocomposites with specific structure and mechanical properties through a control of the filler-polymer interface.