Wang Yongzhen, Cheng Zhongjun, Liu Zhenguo, Kang Hongjun, Liu Yuyan
MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
J Mater Chem B. 2018 Mar 21;6(11):1668-1677. doi: 10.1039/c7tb03069j. Epub 2018 Mar 1.
Water-responsive shape-memory materials, especially cellulose nanofibers (CNF)-polymer composite materials, have been rapidly developed in recent years for designing new generation water-responsive sensors, actuators, biomedical devices, etc. However, achieving fast-responsivity is still a challenge. Herein, by simply incorporating CNF into a thermoplastic elastomer polyurethane (PU) matrix, we report a material, namely, PU/CNF nanocomposite, which has a good shape memory effect (SME) and fast responsivity. The effects of the CNF content on water absorption, shape memory behavior and mechanical properties of the composites are studied, and it can be found that when the CNF content reaches 30%, materials with good SME, such as high shape fixing and shape recovery ratio (higher than 90%) and fast responsivity (less than 1 min), can be obtained. The excellent SME can be ascribed to the combined effect of the good elastic recovery property of the PU matrix, high modulus of CNF and the rapid water uptake behavior of PU/CNF, based on which a rigid CNF percolation network in the elastomeric PU can be formed/destroyed by the desorption/absorption of water molecules repeatedly. Finally, based on the excellent rapid water-triggered shape memory performance, we also demonstrate some applications of the material, for example, as a "mechanical hand" to grasp solid objects in water and as a smart sealing film to build a controllable release system.
近年来，水响应形状记忆材料，尤其是纤维素纳米纤维（CNF）-聚合物复合材料，在设计新一代水响应传感器、致动器、生物医学装置等方面得到了迅速发展。然而，实现快速响应仍然是一个挑战。在此，通过简单地将CNF掺入热塑性弹性体聚氨酯（PU）基体中，我们报道了一种具有良好形状记忆效应（SME）和快速响应性的材料，即PU/CNF纳米复合材料。研究了CNF含量对复合材料吸水率、形状记忆行为和力学性能的影响，发现当CNF含量达到30%时，可以获得具有良好SME的材料，如高形状固定率和形状恢复率（高于90%）以及快速响应性（小于1分钟）。优异的SME可归因于PU基体良好的弹性恢复性能、CNF的高模量以及PU/CNF快速的吸水行为的综合作用，基于此，弹性体PU中刚性的CNF渗流网络可通过水分子的解吸/吸收反复形成/破坏。最后，基于优异的快速水触发形状记忆性能，我们还展示了该材料的一些应用，例如，作为“机械手”在水中抓取固体物体以及作为智能密封膜构建可控释放系统。
