Revealing thermophysical and mechanical responses of graphene-reinforced polyvinyl alcohol nanocomposites using molecular dynamics simulations

The effects of graphene (G) nanofiller content on enhancing the mechanical and thermal resistance of the polyvinyl alcohol (PVA) matrix are disentangled by performing all-atom classical molecular dynamics (MD) simulations. The crux of the computational work is to assess several key performance-limiting factors of the functional hybrid material, including the strain rate, temperature, and the size and distribution of the graphene nanofiller. Adding graphene nanofiller to the polymer results in more compact polymer chains, with the most significant impact observed in the 2% graphene composite. Uniaxial compression MD simulations revealed that the yield strength of the material is impacted by the proportion of nanofiller present. Specifically, the calculated stress-strain responses at a strain rate of 1.5 × 10⁸ s^-1 show that incorporating 2% graphene nanofiller remarkably enhances the yield strength. Conversely, increasing the graphene content to 5-10% led to a reduction in yield stress, which is primarily attributed to the disruption of hydrogen bond networks and destabilization of non-covalent interactions. Further analysis shows that increasing the strain rate led to higher yield stress in the G-PVA composite, while elevated temperatures caused its yield stress to decrease. Additionally, the glass transition temperature of the PVA composite rises with the graphene content and strongly correlates with the polymer chain mobility. The proposed theoretical approach may serve as a quantitative framework for elucidating the crucial role of interfacial interaction between polymers and nanomaterials in modulating the conformational, thermodynamic, and macroscopic properties of the hybrid materials.