Anomalous scaling law of strength and toughness of cellulose nanopaper
Anomalous scaling law of strength and toughness of cellulose nanopaper
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DOI：
10.1073/pnas.1502870112
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发表时间：
2015-07
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影响因子：
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通讯作者：
Hongli Zhu;Shuze Zhu;Z. Jia;Sepideh Parvinian;Yuanyuan Li;Oeyvind Vaaland;Liangbing Hu;Teng Li
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文献类型：
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作者：
Hongli Zhu;Shuze Zhu;Z. Jia;Sepideh Parvinian;Yuanyuan Li;Oeyvind Vaaland;Liangbing Hu;Teng Li
材料设计中一个长期存在的挑战是克服强度和韧性之间的冲突，因为它们通常是相互排斥的。为了应对这一挑战，我们合理地设计了纤维素基纳米纸，并研究了其机械性能对组成纤维素纤维尺寸的依赖性。令人惊讶的是，我们发现纳米纸的强度和韧性同时增加（分别为40和130倍），因为组成纤维素纤维的平均直径从27 μm减小到11 nm，这表明有希望的潜力朝着一个异常但非常理想的比例定律：越小，越强，越坚韧。有大量的机会使用基本的自下而上的策略来设计一类既坚固又坚韧的新型功能材料。在先进的材料设计中，对强度和韧性的追求是永恒的;不幸的是，这两种机械性能通常是相互排斥的。到目前为止，在获得强度和韧性方面只取得了有限的成功，这通常需要特定材料的复杂或昂贵的合成工艺，因此很难适用于其他材料。解决实力与韧性之间冲突的一般机制仍然难以捉摸。在这里，我们报告了纤维素纳米纸的强度和韧性对组成纤维素纤维的尺寸的依赖性的首次同类研究。令人惊讶的是，我们发现，纤维素纳米纸的强度和韧性同时增加（40和130倍，分别）作为组成纤维素纤维的尺寸减小（从27 μm到11 nm的平均直径），揭示了纤维素纳米纸的机械性能的异常但非常理想的比例法则：越小，越强，越坚韧。进一步的基本机理研究表明，减少内在缺陷的大小和纤维素分子链之间的强氢键的容易（重新）形成是这种新的机械性能的标度律的潜在关键。这些机械发现通常适用于其他材料构建块，因此为使用基本的自下而上策略设计一类既坚固又坚韧的新功能材料提供了大量机会。
Significance A long-standing challenge in material design is to overcome the conflict between strength and toughness, because they are generally mutually exclusive. To address this challenge, we rationally design cellulose-based nanopaper and investigate the dependence of their mechanical properties on constituent cellulose fiber size. Surprisingly, we find that both the strength and toughness of the nanopaper increase simultaneously (40 and 130 times, respectively) as the average diameter of constituent cellulose fibers decreases from 27 μm to 11 nm, suggesting the promising potential toward an anomalous but highly desirable scaling law: the smaller, the stronger and the tougher. There are abundant opportunities to use the fundamental bottom-up strategy to design a novel class of functional materials that are both strong and tough. The quest for both strength and toughness is perpetual in advanced material design; unfortunately, these two mechanical properties are generally mutually exclusive. So far there exists only limited success of attaining both strength and toughness, which often needs material-specific, complicated, or expensive synthesis processes and thus can hardly be applicable to other materials. A general mechanism to address the conflict between strength and toughness still remains elusive. Here we report a first-of-its-kind study of the dependence of strength and toughness of cellulose nanopaper on the size of the constituent cellulose fibers. Surprisingly, we find that both the strength and toughness of cellulose nanopaper increase simultaneously (40 and 130 times, respectively) as the size of the constituent cellulose fibers decreases (from a mean diameter of 27 μm to 11 nm), revealing an anomalous but highly desirable scaling law of the mechanical properties of cellulose nanopaper: the smaller, the stronger and the tougher. Further fundamental mechanistic studies reveal that reduced intrinsic defect size and facile (re)formation of strong hydrogen bonding among cellulose molecular chains is the underlying key to this new scaling law of mechanical properties. These mechanistic findings are generally applicable to other material building blocks, and therefore open up abundant opportunities to use the fundamental bottom-up strategy to design a new class of functional materials that are both strong and tough.