Porosity Governs Normal Stresses in Polymer Gels
Porosity Governs Normal Stresses in Polymer Gels
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DOI：
10.1103/physrevlett.117.217802
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发表时间：
2016-11-18
影响因子：
8.6
通讯作者：
Bonn, Daniel
中科院分区：
文献类型：
--
作者：
de Cagny, Henri C. G.;Vos, Bart E.;Bonn, Daniel
当剪切时，大多数弹性固体包括金属、橡胶和聚合物凝胶垂直于剪切平面膨胀。这种行为被称为坡印廷效应，其特征在于正的法向应力。令人惊讶的是，纤维状生物聚合物凝胶在剪切下表现出负的法向应力。在这里，我们表明，这种异常的行为起源于生物聚合物凝胶的开放网络结构。使用具有可控孔径的纤维蛋白网络作为模型系统，我们表明，所施加的剪切的正应力响应在短时间内是正的，但随着孔径设置的特征时间尺度减小到负值。使用双流体模型，我们开发了一个定量的理论，统一的合成和生物聚合物凝胶中遇到的相反的行为。
When sheared, most elastic solids including metals, rubbers, and polymer gels dilate perpendicularly to the shear plane. This behavior, known as the Poynting effect, is characterized by a positive normal stress. Surprisingly, fibrous biopolymer gels exhibit a negative normal stress under shear. Here we show that this anomalous behavior originates from the open-network structure of biopolymer gels. Using fibrin networks with a controllable pore size as a model system, we show that the normal-stress response to an applied shear is positive at short times, but decreases to negative values with a characteristic time scale set by pore size. Using a two-fluid model, we develop a quantitative theory that unifies the opposite behaviors encountered in synthetic and biopolymer gels.