Designing High-Performance Cellulose-Nanofiber Thermoplastic Polymer Composites Through Multi-Scale MD Simulations

Cellulose nanofibers (CNFs) are excellent reinforcing materials for high-performance polymer nanocomposites due to their exceptional mechanical strength and sustainability. Improving their compatibility with polymer matrices, however, is challenging due to the strong inter-CNF interactions resulting in irreversible agglomeration. We performed classical and coarse-grained molecular dynamics (MD) simulations of native and surface-modified CNFs in thermoplastic polymer matrices: polypropylene, polyethylene terephthalate glycol, polylactic acid and poly-(3-hydroxybutyrate) that are promising candidates for bio-based 3-D printed nanocomposites. We computed CNF-polymer interaction energies and radial distribution functions using atomistic models to understand the molecular interactions between various groups in CNFs and the polymer chains. We further evaluated tensile modulus of these nanocomposites under varying fiber alignment conditions using non-equilibrium coarse-grained MD simulations to investigate the effect of CNF-polymer interactions on the tensile strength and failure mode. We observe a significant change in mechanical strength and CNF-polymer interaction energies with varying surface modifications and polymer matrices. Our predictions provide valuable insights for designing high-performance bio nanocomposites through a fundamental understanding of physico-chemical interactions in these materials.