Buckling Mechanics Modulus Measurement of Anisotropic Cellulose Nanocrystal Thin Films
Buckling Mechanics Modulus Measurement of Anisotropic Cellulose Nanocrystal Thin Films
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DOI：
10.1021/acsapm.1c01514
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发表时间：
2022-05-13
影响因子：
5
通讯作者：
Davis, Chelsea S.
中科院分区：
文献类型：
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作者：
Miller, Nolan A.;Li, Zhaofan;Davis, Chelsea S.
生物衍生材料已经成为替代来自不可再生资源的材料的一种越来越受欢迎的选择。纤维素纳米晶(CNCs)通常从木浆中提取，可用于制造薄膜，应用范围从光学、保护和美学涂层到传感器和电池。量化数控薄膜的机械性能是提高这些生物衍生薄膜质量的必要步骤。由于碳纳米管是高度各向异性的，因此可以形成高度有序的、排列的结构，因此有一种实验方法可以简洁地确定薄膜的性质如何随着颗粒取向的变化而变化。在这里，将碳纳米管的水溶液旋涂在有机硅弹性体上可以得到径向排列的颗粒组装。随着这些排列的、高纵横比颗粒的局部取向相对于单轴压缩而改变，观察到颗粒组件的机械响应显著不同。对径向排列的数控薄膜/弹性体双层施加横向压缩会导致表面屈曲与压缩方向垂直对齐。这些皱纹的波长，再加上薄膜的厚度和衬底的模数，由薄膜的模数决定。因此，在单个实验中确定了作为每个膜的局部cnc排列和位置的函数的模数。这些实验测量了薄膜的较高模数，其中纳米颗粒的取向平行于单轴压缩方向。对紧密堆积、高纵横比的颗粒集合体的粗粒度建模支持实验结果，与观察到的趋势一致。对数控薄膜的力学性能进行表征，可以使这些绿色材料进一步发展成工业规模的应用；此外，还提出了一种实验方法，可以简明地获取各向异性颗粒薄膜中的一系列模量值。
Bioderived materials have become an increasingly desirable alternative to materials sourced from nonrenewable resources. Cellulose nanocrystals (CNCs), often derived from wood pulp, can be used to manufacture thin films with applications ranging from optical, protective, and aesthetic coatings to sensors and batteries. Quantifying the mechanical properties of CNC films is a necessary step toward improving the quality of these bioderived films. Because CNCs are highly anisotropic and can subsequently form highly ordered, aligned structures, an experimental method that can succinctly determine how film properties change with particle orientation is of interest. Here, spin coating an aqueous solution of CNCs onto a silicone elastomer results in a radially aligned particle assembly. As the local orientation of these aligned, high aspect ratio particles changes with respect to a uniaxially applied compression, the mechanical response of the particle assembly was observed to vary significantly. Applying a lateral compression to a radially aligned CNC film/elastomer bilayer caused surface buckles to align orthogonal to the compression direction. The wavelength of these wrinkles, coupled with the thickness of the film and the modulus of the substrate, is dictated by the modulus of the film. The modulus as a function of local CNC alignment and position for each film was thus determined in a single experiment. These experiments measured a higher modulus for the film where the orientation of the CNC particles is aligned parallel to the uniaxial compression direction. Coarse-grained modeling of closely packed, high aspect ratio particle assemblies supporting the experimental results agrees with the observed trend. Characterizing the mechanical properties of CNC films can allow for these green materials to be further developed for industrial-scale implementation; additionally, an experimental method is proposed for concisely capturing a range of modulus values in an anisotropic particle film.