Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland.
Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States.
Biomacromolecules. 2021 Dec 13;22(12):5087-5096. doi: 10.1021/acs.biomac.1c01056. Epub 2021 Nov 4.
On account of their high strength and stiffness and their renewable nature, cellulose nanocrystals (CNCs) are widely used as a reinforcing component in polymer nanocomposites. However, CNCs are prone to aggregation and this limits the attainable reinforcement. Here, we show that nanocomposites with a very high CNC content can be prepared by combining the cationic polymer poly[(2-(methacryloyloxy)ethyl) trimethylammonium chloride] (PMETAC) and negatively charged, carboxylated CNCs that are provided as a sodium salt (CNC-COONa). Free-standing films of the composites can be prepared by simple solvent casting from water. The appearance and polarized optical microscopy and electron microscopy images of these films suggest that CNC aggregation is absent, and this is supported by the very pronounced reinforcement observed. The incorporation of 33 wt % CNC-COONa into PMETAC allowed increasing the storage modulus of this already rather stiff, glassy amorphous matrix polymer from 1.5 ± 0.3 to 6.6 ± 0.1 GPa, while the maximum strength increased from 11 to 32 MPa. At this high CNC content, the reinforcement achieved in the PMETAC/CNC-COONa nanocomposite is much more pronounced than that observed for a reference nanocomposite made with unmodified CNCs (CNC-OH).
由于其高强度和高刚性以及可再生性，纤维素纳米晶体 (CNC) 被广泛用作聚合物纳米复合材料中的增强组分。然而，CNC 容易聚集，这限制了可达到的增强效果。在这里，我们展示了通过将阳离子聚合物聚[(2-(甲基丙烯酰氧基)乙基)三甲基氯化铵] (PMETAC) 与带负电荷的、以钠盐形式提供的羧基化 CNC(CNC-COONa) 结合，可以制备具有非常高 CNC 含量的纳米复合材料。通过简单的溶剂浇铸从水中可以制备出复合材料的自支撑薄膜。这些薄膜的外观和偏光显微镜和电子显微镜图像表明不存在 CNC 聚集，这得到了观察到的非常明显的增强的支持。将 33wt%的 CNC-COONa 掺入 PMETAC 中，使得这种已经相当硬的、玻璃态无定形基质聚合物的储能模量从 1.5±0.3 GPa 增加到 6.6±0.1 GPa，而最大强度从 11 MPa 增加到 32 MPa。在这种高 CNC 含量下，在 PMETAC/CNC-COONa 纳米复合材料中实现的增强效果比用未改性 CNC（CNC-OH）制备的参考纳米复合材料明显得多。
