Atomistic Insights into Transport Properties of Polylactic Acid/Graphene Oxide Nanocomposites Using Molecular Dynamics Simulations

Abstract

This study explores the role of graphene oxide (GO) as a nanofiller in polylactic acid (PLA)-based nanocomposites using molecular dynamics (MD) simulations. A systematic variation in loading percentage, sheet size, and the number of GO sheets was employed to assess the impact on material performance. The findings reveal that GO incorporation significantly affects gas diffusion through the polymer matrix. Free volume analysis corroborates these trends, showing strong relation with diffusion behavior. Nanocomposites with larger GO sheets (3 × 4 nm2) exhibit the lowest fractional accessible volume (FAV %) for all probe radii (0 Å, 1.4 Å, 1.52 Å, and 1.64 Å) compared to those with medium (2 × 3 nm2) and smaller (1 × 2 nm2) GO sheets, indicating that decreasing sheet size increases the available free volume and promotes more efficient molecular transport. Additionally, increasing the number of GO sheets (with dimensions of 2 × 3 nm2) enhances free volume, promotes gas diffusion, and lowers viscosity under the investigated simulation conditions. Overall, this work presents an atomistic-level investigation of the impact of GO on the free volume, diffusion of gases, and rheological behavior of PLA using MD simulations, emphasizing the importance of GO size and loading on PLA nanocomposite performance.