Department of Physics and Astronomy, Vrije Universiteit, 1081-HV Amsterdam, The Netherlands and Department of Applied Physics and Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600-MB Eindhoven, The Netherlands.
Radboud University Nijmegen, Institute for Molecules and Materials, Department of Molecular Materials, 6525-AJ Nijmegen, The Netherlands.
Soft Matter. 2016 Aug 17;12(33):6995-7004. doi: 10.1039/c6sm01033d.
In this paper we study the elastic response of synthetic hydrogels to an applied shear stress. The hydrogels studied here have previously been shown to mimic the behaviour of biopolymer networks when they are sufficiently far above the gel point. We show that near the gel point they exhibit an elastic response that is consistent with the predicted critical behaviour of networks near or below the isostatic point of marginal stability. This point separates rigid and floppy states, distinguished by the presence or absence of finite linear elastic moduli. Recent theoretical work has also focused on the response of such networks to finite or large deformations, both near and below the isostatic point. Despite this interest, experimental evidence for the existence of criticality in such networks has been lacking. Using computer simulations, we identify critical signatures in the mechanical response of sub-isostatic networks as a function of applied shear stress. We also present experimental evidence consistent with these predictions. Furthermore, our results show the existence of two distinct critical regimes, one of which arises from the nonlinear stretch response of semi-flexible polymers.
本文研究了合成水凝胶在切应力作用下的弹性响应。这里研究的水凝胶以前曾被证明在远高于凝胶点时可以模拟生物聚合物网络的行为。我们表明，在接近凝胶点时，它们表现出的弹性响应与网络在等静压点附近或以下的临界行为一致，等静压点将刚性和柔软状态分开，其区别在于是否存在有限的线性弹性模量。最近的理论工作也集中在这种网络对有限或大变形的响应上，包括在等静压点附近和以下的情况。尽管有这样的兴趣，但在这种网络中存在临界性的实验证据一直缺乏。我们使用计算机模拟，确定了亚等静压网络在切应力作用下的力学响应中的临界特征。我们还提供了与这些预测一致的实验证据。此外，我们的结果表明存在两种不同的临界状态，其中一种状态是由半柔性聚合物的非线性拉伸响应引起的。
