我组（18T7组）在纤维素纳米晶研究方面取得新进展。纤维素纳米晶体(CNCs)是制造生物源彩色薄膜的强大光子组装体。自组装CNCs和多种模板剂的优势的结合，为新型物理化学传感器、结构涂层和光学设备的开发提供了途径。然而，由于CNC衍生材料固有的脆性和水不稳定性，其进一步的应用受到广泛的质疑和限制。为此我们将软的聚乙烯醇（PVA）聚合物引入到刚性CNC系统中，以平衡CNC分子之间的相互作用。随后，通过戊二醛（GA）的交联反应将两种有序组装的硬/软纳米复合材料固定，紧接着通过蒸发诱导的自组装技术制备高度柔性，水稳定性和光子结构色的CNC复合膜。对于1.5 wt％GA交联的70 wt％CNCs加载膜，用苛刻的亲水性暴露（浸泡在强酸，强碱和海水中）和各种有机溶剂进行处理，这些薄膜均展现出优异的耐溶剂性能。另外，该薄膜可以承受166 g cm-2的重量而不会失效。这是一种高度坚硬和耐用的特性。重要的是，该膜仍是高度有序的手性向列型结构，能够用作高度透明的底物，用于选择性反射左旋圆偏振光。我们的工作将为低成本和耐用的光子纤维素涂层应用铺平道路。
Highly Strong and Solvent Resistant Cellulose Nanocrystal Photonic Films for Optical Coatings
Fusheng Zhang, Wenna Ge, Cunli Wang, Xintong Zheng, Dongdong Wang, Xiancheng, Zhang, Xue Wang, Xingya Xue and Guangyan Qing*
ACS Appl. Mater. Interfaces 2021, 13, 17118--17128; DOI: 10.1021/acsami.1c02753
Cellulose nanocrystals (CNCs) are powerful photonic building blocks for the fabrication of biosourced colored films. A combination of the advantages of self-assembled CNCs and multiple templating agents offers access to the development of novel physicochemical sensors, structural coatings, and optic devices. However, due to the inherent brittleness and water instability of CNC-derived materials, their further applications are widely questionable and restrictive. Here, a soft polymer of polyvinyl alcohol (PVA) was introduced into the rigid CNC system to balance molecular interactions. Whereafter, two hard/soft nanocomposites are fastened through a cross-linking reaction of glutaraldehyde (GA), resulting in a highly flexible, water-stability, and chiral nematic CNC composite film through evaporation-induced self-assembly technique. For a 1.5 wt% GA-crosslinked 70 wt% CNCs loading film, treatment of it with harsh hydrophilic exposure (soaking in a strong acid, strong base, and seawater) and various organic solvents shows exceptional solvent resistance abilities. Furthermore, the film can even withstand a weight of 167 g cm-2 without failure, which is a highly stiff and durable character. Importantly, the film remains a highly ordered chiral nematic organization, being able to act as a highly transparent substrate for selective reflection of left-handed circularly polarized light, preparing fully covered and patterned full-color coatings on various substrates. Our work will pave the way for applications in low-cost, durable, and photonic cellulosic coatings.
