Behavior and mechanics of dense microgel suspensions
Behavior and mechanics of dense microgel suspensions
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DOI：
10.1073/pnas.2008076117
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发表时间：
2020-11-03
影响因子：
11.1
通讯作者：
Alexeev, Alexander
中科院分区：
文献类型：
--
作者：
Nikolov, Svetoslav, V;Fernandez-Nieves, Alberto;Alexeev, Alexander
软的和高度可变形的微凝胶的悬浮液可以比硬胶体的悬浮液浓缩得多，从而导致其不寻常的机械性能。微凝胶可以以多种方式适应悬浮液中的压缩，例如相互渗透、变形和收缩。以前的实验提供了有见地的，但有点矛盾，在压缩悬浮液中的单个微凝胶的行为帐户。我们开发了一个介观尺度的计算模型，以探测在各种包装分数和溶剂条件下，由不同结构的微凝胶组成的压缩悬浮液的行为。我们发现，微凝胶主要改变形状和轻微收缩以上的随机紧密包装。仅在空间填充上方可察觉到互穿，相对于交联之间的平均距离保持较小。在甚至更高的填充分数下，微凝胶仅收缩。值得注意的是，无论单微凝胶的性质如何，以及悬浮液浓度是否通过改变颗粒数密度或颗粒的溶胀状态而改变，这甚至可以导致胶态凝胶化，悬浮液的力学可以根据单微凝胶的体积模量来量化，因此这成为这些类型的软胶体悬浮液的正确力学量度。我们的研究结果合理化的许多不同的实验结果，提供洞察力的相对重要性的影响定义的力学悬浮液包括软颗粒。
Suspensions of soft and highly deformable microgels can be concentrated far more than suspensions of hard colloids, leading to their unusual mechanical properties. Microgels can accommodate compression in suspensions in a variety of ways such as interpenetration, deformation, and shrinking. Previous experiments have offered insightful, but somewhat conflicting, accounts of the behavior of individual microgels in compressed suspensions. We develop a mesoscale computational model to probe the behavior of compressed suspensions consisting of microgels with different architectures at a variety of packing fractions and solvent conditions. We find that microgels predominantly change shape and mildly shrink above random close packing. Interpenetration is only appreciable above space filling, remaining small relative to the mean distance between cross-links. At even higher packing fractions, microgels solely shrink. Remarkably, irrespective of the single-microgel properties, and whether the suspension concentration is changed via changing the particle number density or the swelling state of the particles, which can even result in colloidal gelation, the mechanics of the suspension can be quantified in terms of the single-microgel bulk modulus, which thus emerges as the correct mechanical measure for these type of softcolloidal suspensions. Our results rationalize the many and varied experimental results, providing insights into the relative importance of effects defining the mechanics of suspensions comprising soft particles.