Nonlinear elasticity of stiff filament networks: strain stiffening, negative normal stress, and filament alignment in fibrin gels.
Nonlinear elasticity of stiff filament networks: strain stiffening, negative normal stress, and filament alignment in fibrin gels.
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DOI：
10.1021/jp807749f
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发表时间：
2009-03-26
期刊：
影响因子：
--
通讯作者：
MacKintosh FC
中科院分区：
文献类型：
--
作者：
Kang H;Wen Q;Janmey PA;Tang JX;Conti E;MacKintosh FC
许多由交联的半柔性或刚性长丝形成的生物材料在样品以简单剪切几何形状变形时表现出应变硬化和负法向应力形式的非线性流变学。已经开发了两种不同的理论模型来解释这种非线性弹性响应，这既不是由橡胶弹性理论预测的，也不是在弹性体或由柔性聚合物形成的凝胶中观察到的。一个模型考虑了半柔性聚合物的各向同性网络的响应，这些聚合物具有由其热波动引起的非线性力-伸长率关系。另一个考虑网络的刚性长丝与线性力的伸长关系，其中非线性产生的非仿射变形和转移从长丝弯曲拉伸增加应变。纤维蛋白凝胶是测试这些理论的良好实验系统，因为纤维蛋白单体在不同条件下组装以形成具有网络网孔尺寸量级的持久长度的热波动的原纤维或更厚的刚性纤维。流变学和光学测量的比较表明，应变硬化和负法向应力出现在较小的应变比那些长丝取向是明显的双折射。剪切法向应力和剪切模量和双折射率的应变依赖性的比较建议的方法来评估不同的棒状聚合物网络理论的适用性。正应力与剪应力之比的应变依赖性是区分半柔性和刚性细丝模型的一个参数，并且与实验的比较揭示了特定理论可能适用的条件。
Many biomaterials formed by crosslinked semiflexible or rigid filaments exhibit non-linear rheology in the form of strain-stiffening and negative normal stress when samples are deformed in simple shear geometry. Two different classes of theoretical models have been developed to explain this non-linear elastic response, which is neither predicted by rubber elasticity theory nor observed in elastomers or gels formed by flexible polymers. One model considers the response of isotropic networks of semiflexible polymers that have non-linear force-elongation relations arising from their thermal fluctuations. The other considers networks of rigid filaments with linear force-elongation relations in which non-linearity arises from non-affine deformation and a shift from filament bending to stretching at increasing strains. Fibrin gels are a good experimental system to test these theories because the fibrin monomer assembles under different conditions to form either thermally fluctuating protofibrils with persistence length on the order of the network mesh size, or thicker rigid fibers. Comparison of rheologic and optical measurements shows that strain stiffening and negative normal stress appear at smaller strains than those at which filament orientation is evident from birefringence. Comparisons of shear to normal stresses and the strain-dependence of shear moduli and birefringence suggest methods to evaluate the applicability of different theories of rod-like polymer networks. The strain-dependence of the ratio of normal stress to shear stress is one parameter that distinguishes semi-flexible and rigid filament models, and comparisons with experiments reveal conditions under which specific theories may be applicable.
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影响因子：
3.3
作者：
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