Effects of different functional groups in graphene nanofiber on the mechanical property of polyvinyl alcohol composites by the molecular dynamic simulations

Polyvinyl alcohol (PVA) matrix composites reinforced by functional graphene nanofiber (FGF) characterized by different functional groups were investigated to identify the mechanical properties of PVA/FGF composites employing the molecular dynamic (MD) simulations. The influences of the distributions of different functional groups (-COOH, -CONH3, -O-, and -OH) on the mechanical properties of PVA/FGF and the interfacial interaction between PVA and FGF have been explored. It was found that FGF can improve the elasticity modulus, the tensile strength, and stretchability of the composites. Generally, the more oxygen-containing functional groups, the greater the influences on these properties of the composites. Meanwhile, the arrangements of the functional groups bounded to graphene also have influences on the mechanical properties of materials, i.e., the edge functional graphene nanofiber with -OH and -COOH functional groups can greatly improve the mechanical properties of materials compared to the functional groups in other positions. Moreover, the effects of the different aspect ratios of FGF on the mechanical properties of composites have been studied. It was found that the mechanical properties of composites were enhanced with the increase of the aspect ratios of FGF in a certain range. In addition, analyses of results for the radius of gyration (Rg), radial distribution function (RDF), interaction energy, and mean squared displacement (MSD) of PVA molecular chains indicate that PVA molecular chains are extended along the surface of FGF and lots of hydrogen bonds and strong interaction between PVA and FGF have been observed, suggesting that the addition of FGF limits the movement of PVA molecular chains.