Xu Guofan, Laverock Jude, Koev Todor T, Khimyak Yaroslav Z, Diejomaoh Onajite Abafe, Rochat Sebastien, Eichhorn Stephen J
Bristol Composites Institute, School of Civil, Aerospace and Design Engineering, University of Bristol, University Walk, Bristol BS8 1TR, U.K.
School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K.
ACS Appl Polym Mater. 2025 Apr 16;7(8):4982-4991. doi: 10.1021/acsapm.5c00219. eCollection 2025 Apr 25.
A cellulose nanocrystal (CNC)-polyvinyl acetate (PVAc) self-healing composite film was fabricated using a grafting-from approach generating polyvinyl acetate (PVAc) chains on CNC macroinitiators. These grafted-to CNCs were then mixed with bulk PVAc polymer to form a composite. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and solid-state nuclear magnetic resonance were used to demonstrate the presence of the grafted PVAc chains on the surface of the CNCs. Transmission electron microscopy images revealed the structure of the modified CNCs, which formed closely packed clusters due to the grafted PVAc chains. The thermal properties of the CNCs and their composite films were assessed by using differential scanning calorimetry, determining the appropriate temperature for the healing of the composite film. On this basis, the film was cut into two pieces and rejoined and healed in an oven heated at 40 °C for 6 h. The healed sample was viewed under an optical microscope and electron microscopy, demonstrating the efficacy of the healing process. An array of microindentation tests across the surface of the healed specimen was conducted to quantify stiffness, revealing no detectable differences between the healed and intact regions. This healing was found to only occur for the grafted-to samples and was not evident for the composites made of PVAc and ungrafted CNCs. This work demonstrates that grafting polymer chains onto CNCs and blending these with a bulk polymer are promising approaches for fabricating composite films capable of healing macroscopic fractures.
采用从引发剂接枝的方法，在纤维素纳米晶体（CNC）大分子引发剂上生成聚醋酸乙烯酯（PVAc）链，制备了一种CNC-聚醋酸乙烯酯（PVAc）自愈合复合膜。然后将这些接枝到CNC上的聚合物与本体PVAc聚合物混合形成复合材料。利用傅里叶变换红外光谱、X射线光电子能谱和固态核磁共振来证明接枝的PVAc链存在于CNC表面。透射电子显微镜图像揭示了改性CNC的结构，由于接枝的PVAc链，其形成了紧密堆积的簇。通过差示扫描量热法评估CNC及其复合膜的热性能，确定复合膜愈合的合适温度。在此基础上，将薄膜切成两片，重新连接并在40℃加热的烘箱中愈合6小时。在光学显微镜和电子显微镜下观察愈合后的样品，证明了愈合过程的有效性。对愈合后试样表面进行了一系列微压痕试验以量化刚度，结果表明愈合区域和未损伤区域之间没有可检测到的差异。发现这种愈合仅发生在接枝到的样品上，而对于由PVAc和未接枝的CNC制成的复合材料则不明显。这项工作表明，将聚合物链接枝到CNC上并将其与本体聚合物共混是制备能够愈合宏观裂缝的复合膜的有前途的方法。
