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 the 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 a 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 is more associated with the degree of local packing and density rather than the CNC orientation. Our study provides fundamental insights into deformational mechanisms associated with the microstructure and dynamics of CNC films at a molecular level, aiding in the tailored design of cellulose-based materials for their mechanical performance.

纤维素纳米晶体 (CNC) 薄膜因其与动态和微观结构特征相关的优异机械和物理特性而在工程和技术应用中引起了极大的兴趣。在这里，我们采用粗粒分子动力学 (CG-MD) 模拟来研究在拉伸变形下 CNC 薄膜的动力学和微观结构如何变化。我们的结果表明，杨氏模量可以通过与初始堆积密度的幂律比例关系进行定量预测，其中较高的密度导致模量和强度的增加。通过评估拉伸过程中的分子局部刚度，我们的研究结果表明，具有更高密度的 CNC 薄膜表现出更高程度的动态不均匀性，在变形下大大降低。我们的结果进一步表明，随机取向的 CNC 倾向于与拉伸方向更一致，在变形过程中与更高的自由体积和孔隙率相关；然而，CNC 的动力学更多地与局部包装和密度的程度有关，而不是与 CNC 的方向有关。我们的研究提供了在分子水平上与 CNC 薄膜的微观结构和动力学相关的变形机制的基本见解，有助于针对纤维素基材料的机械性能进行量身定制的设计。