Microstructure and Dynamics of Nanocellulose Network: Insights into the Deformational Behaviors

Cellulose nanocrystals (CNCs) thin films draw considerable interest in engineering and technological applications due to their excellent mechanical and physical properties associated with dynamic and microstructural features. Here, we employ coarse-grained molecular dynamics (CG-MD) simulations to investigate how the dynamics and microstructure change in the CNC films under tensile deformation. Our results show that the Young's modulus can be quantitatively predicted by power-law scaling relationship with initial packing density, where higher density leads to an increase in both modulus and strength. By evaluating the molecular local stiffness during the tensile process, our findings show that CNC film with higher density exhibits a higher degree of dynamic heterogeneity, which is greatly reduced under deformation. Our results further demonstrate that randomly oriented CNCs tend to be more aligned with the tensile direction associated with higher free volume and porosity during the deformation; however, the dynamics of CNC are more associated with the degree of local packing and density rather than the CNC orientation. Our study provides fundamental insights into deformational mechanisms of CNC films at a molecular level, aiding in the tailored design of cellulose-based materials for their mechanical performance.