标题： 探测单轴应变聚合物网络中的微观动力学 显示英文标题

标题： Probing microscopic dynamics in a uni-axially strained polymer network

摘要： 我们介绍了一种新装置，可同时探测聚合物网络在单轴应变下的宏观机械响应和微观运动。 该装置利用光子关联成像，这是一种空间和时间分辨的动态光散射方法，用于测量沿三个正交方向以及在两个不同长度尺度上的动力学特性，从几十纳米到几微米。 我们展示了如何避免由于聚合物薄膜表面散射引起的伪影，并推导出由于纯仿射变形产生的强度关联函数的理论表达式，表明通过改变收集光学器件的接受角可以简单地调节装置的灵敏度。 最后，我们通过研究线性区域内拉伸应变下聚二甲基硅氧烷聚合物网络的微观动力学，展示了该装置的能力。 我们发现，在小于几微米的长度尺度上，非仿射动力学占主导地位，而在其以上长度尺度则恢复了仿射响应。 令人惊讶的是，分隔非仿射和仿射区域的交叉长度随着施加的拉伸应变的减小而\textit{增加}。 显示英文摘要

摘要： We present a new apparatus that probes simultaneously the macroscopic mechanical response and the microscopic motion in polymer networks under uni-axial strain. The setup leverages photon correlation imaging, a space- and time-resolved dynamic light scattering method, to measure the dynamics along three orthogonal directions and on two distinct length scales, from tens of nanometers to a couple of microns. We show how to avoid artifacts due to scattering from the surface of the polymer films and derive a theoretical expression for the intensity correlation function due to a purely affine deformation, showing that the setup sensitivity may be simply tuned by varying the acceptance angle of the collection optics. Finally, we demonstrate the capabilities of the setup by investigating the microscopic dynamics of a poly(dimethylsiloxne) polymer network under tensile strain in the linear regime. We find that non-affine dynamics dominate on length scales smaller than a few microns, above which the affine response is recovered. Surprisingly, the cross-over length separating the non-affine and affine regimes \textit{increases} upon decreasing the applied tensile strain.