Department of Physics, and Center for Theoretical Biological Physics, University of California, San Diego, La Jolla, California 92093, USA.
J Chem Phys. 2013 Mar 28;138(12):12A521. doi: 10.1063/1.4773349.
Signatures of glassy dynamics have been identified experimentally for a rich variety of materials in which molecular networks provide rigidity. Here we present a theoretical framework to study the glassy behavior of both passive and active network materials. We construct a general microscopic network model that incorporates nonlinear elasticity of individual filaments and steric constraints due to crowding. Based on constructive analogies between structural glass forming liquids and random field Ising magnets implemented using a heterogeneous self-consistent phonon method, our scheme provides a microscopic approach to determine the mismatch surface tension and the configurational entropy, which compete in determining the barrier for structural rearrangements within the random first order transition theory of escape from a local energy minimum. The influence of crosslinking on the fragility of inorganic network glass formers is recapitulated by the model. For active network materials, the mapping, which correlates the glassy characteristics to the network architecture and properties of nonequilibrium motor processes, is shown to capture several key experimental observations on the cytoskeleton of living cells: Highly connected tense networks behave as strong glass formers; intense motor action promotes reconfiguration. The fact that our model assuming a negative motor susceptibility predicts the latter suggests that on average the motorized processes in living cells do resist the imposed mechanical load. Our calculations also identify a spinodal point where simultaneously the mismatch penalty vanishes and the mechanical stability of amorphous packing disappears.
已有研究在分子网络提供刚性的丰富多样的材料中，从实验上识别出玻璃态动力学的特征。在这里，我们提出了一个理论框架来研究被动和主动网络材料的玻璃行为。我们构建了一个通用的微观网络模型，该模型结合了单个纤维的非线性弹性和由于拥挤而产生的空间位阻。基于结构玻璃形成液体和使用非均匀自洽声子方法实现的随机场伊辛磁体之间的结构类比，我们的方案提供了一种微观方法来确定不匹配表面张力和构象熵，它们在决定从局部能量最小的逃逸的随机一级相变理论中的结构重排的势垒方面相互竞争。该模型再现了交联对无机网络玻璃形成体的脆性的影响。对于主动网络材料，将玻璃态特性与网络结构和非平衡马达过程的性质相关联的映射，捕获了关于活细胞细胞骨架的几个关键实验观察：高度连接的紧张网络表现为强玻璃形成体；强烈的马达作用促进了重新配置。我们的模型假设负马达敏感性可以预测后者这一事实表明，平均而言，活细胞中的马达过程确实可以抵抗所施加的机械负载。我们的计算还确定了一个旋节线，在该点上，失配惩罚同时消失，非晶态堆积的力学稳定性也消失。
