Towards the development of high-performance green composites, the surface functionalized cellulose nanocrystals (CNC) have been widely used as reinforcement along with biopolymer. In our previous work, it has been demonstrated that CNC grafted with PDLA (CNC-g-PDLA) could improve the crystal nucleation density and heat distraction ability of PLLA matrix via the PLLA/PDLA stereocomplex interaction. Herein, to understand the role of CNC-g-PDLA on the deformation behavior of PLLA/CNC-g-PDLA nanocomposites, the melt-quenched PLLA/CNC-g-PDLA nanocomposite was uniaxially stretched at 160 °C with various draw ratios. The stretched PLLA/CNC-g-PDLA composites allow us to discriminate the crystal transformation and crystal orientation of three individual components in the composites, that is, (i) PLLA matrix, (ii) PLLA/PDLA stereocomplex existed as interfacial phase, and (iii) CNC reinforcement. The results indicate that PLLA α′ and PLLA/PDLA stereocomplex crystals (β_C) appear at the initial stage of drawing process. The disordered α′ transforms to ordered α and β forms gradually with increasing in draw ratio, whereas β_C-crystals keep almost unchanged during the whole drawing process. The calculation on orientation function of various crystals suggests that the lamellaes of α form have the largest orientation degree along the stretching axis. Meanwhile,CNC nanoparticles and the β_C crystals form the nano-dimensional shish kebab structure during stretching and present relatively low orientation. This study provides the physical insight to guide the preparation of high performance PLLA nanocomposites with hierarchical crystal and orientation structure.

为了开发高性能的绿色复合材料，表面功能化的纤维素纳米晶体（CNC）已与生物聚合物一起被广泛用作增强材料。在我们以前的工作中，已经证明了用PDLA（CNC-g-PDLA）接枝的CNC可以通过PLLA / PDLA立体配合物相互作用提高PLLA基质的晶体成核密度和散热能力。在此，为了理解CNC-g-PDLA对PLLA / CNC-g-PDLA纳米复合材料的变形行为的作用，在160℃下以各种拉伸比将熔融淬火的PLLA / CNC-g-PDLA纳米复合材料单轴拉伸。拉伸的PLLA / CNC-g-PDLA复合材料使我们能够区分复合材料中三个单独成分的晶体转变和晶体取向，即（i）PLLA基质，（ii）PLLA / PDLA立体复合体作为界面相存在，并且（iii）CNC增强。结果表明PLLAα'和PLLA / PDLA立体复合晶体（β_C）出现在绘图过程的初始阶段。无序α'变换以有序α并逐渐与拉伸比增加β形式，而β _Ç -crystals在整个拉伸过程保持几乎没有变化。对各种晶体的取向函数的计算表明，α形薄片沿拉伸轴具有最大的取向度。同时，CNC纳米粒子和β _Ç晶体拉伸和本相对较低的取向期间形成纳米尺寸羊肉串结构。这项研究提供了物理见解，可指导制备具有分层晶体和取向结构的高性能PLLA纳米复合材料。