Tuning the Mechanical Properties of Polymer-Grafted Nanoparticle Networks through the Use of Biomimetic Catch Bonds
Tuning the Mechanical Properties of Polymer-Grafted Nanoparticle Networks through the Use of Biomimetic Catch Bonds
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DOI：
10.1021/acs.macromol.5b02455
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发表时间：
2016-02-23
期刊：
影响因子：
5.5
通讯作者：
Balazs, Anna C.
中科院分区：
文献类型：
--
作者：
Mbanga, Badel L.;Iyer, Balaji V. S.;Balazs, Anna C.
精确调节聚合物复合材料机械性能的能力对于在各种应用中利用这些材料至关重要。交联成网络的聚合物接枝纳米颗粒（PGN）为定制材料的强度和韧性提供了独特的机会。在这些材料中，接枝链的自由端与相邻链形成键，并且定制这些键的性质可以提供定制复合材料的宏观行为的途径。使用计算建模，我们模拟的三维PGN网络，包括高强度的“永久”键和较弱的，更活泼的不稳定的债券的行为。不稳定的连接是由滑动键和仿生“捕获”键形成的。与传统的滑动粘结不同，捕获粘结的寿命可以随着施加的力而增加，因此，这些粘结在变形下变得更强。通过我们的3D模型，我们研究了复合材料对拉伸变形的机械响应，重点关注包含不同数量的永久键、不稳定键之间的不同键能以及不同数量的捕获键的样品。我们发现，在不稳定键的较高能量（U-1 = 39 k（B）T）下，可以通过改变永久键和捕获键的数量来定制材料的机械性能。值得注意的是，通过增加样品中的永久结合或捕获结合的数量（同时保持其他参数固定），可以实现高达2倍的韧性增加。相反，在这里考虑的不稳定键的较低能量（U-1 = 33 k（B）T）下，永久键在调节PGN网络的机械行为中起主导作用。模拟结果为优化PGN网络的宏观行为提供了有价值的指导，并突出了引入捕获键来调节系统机械性能的实用性。
The ability to precisely tune the mechanical properties of polymeric composites is vital for harnessing these materials in a range of diverse applications. Polymer-grafted nanoparticles (PGNs) that are cross-linked into a network offer distinct opportunities for tailoring the strength and toughness of the material. Within these materials, the free ends of the grafted chains form bonds with the neighboring chains, and tailoring the nature of these bonds could provide a route to tailoring the macroscopic behavior of the composite. Using computational modeling, we simulate the behavior of three-dimensional PGN networks that encompass both high-strength "permanent" bonds and weaker, more reactive labile bonds. The labile connections are formed from slip bonds and biomimetic "catch" bonds. Unlike conventional slip bonds, the lifetime of the catch bonds can increase with an applied force, and hence, these bonds become stronger under deformation. With our 3D model, we examined the mechanical response of the composites to a tensile deformation, focusing on samples that encompass different numbers of permanent bonds, different bond energies between the labile bonds, and varying numbers of catch bonds. We found that at the higher energy of the labile bonds (U-l = 39k(B)T), the mechanical properties of the material could be tailored by varying both the number of permanent bonds and catch bonds. Notably, as much as a 2-fold increase in toughness could be achieved by increasing the number of permanent bonds or catch bonds in the sample (while the keeping other parameters fixed). In contrast, at the lower energy of the labile bonds considered here (U-l = 33k(B)T), the permanent bonds played the dominant role in regulating the mechanical behavior of the PGN network. The findings from the simulations provide valuable guidelines for optimizing the macroscopic behavior of the PGN networks and highlight the utility of introducing catch bonds to tune the mechanical properties of the system.