Anomalous Aging and Stress Relaxation in Macromolecular Physical Gels: The Case of Strontium Alginate,Macromolecules

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Anomalous Aging and Stress Relaxation in Macromolecular Physical Gels: The Case of Strontium Alginate
Macromolecules ( IF 5.1 ) Pub Date : 2020-01-10 , DOI: 10.1021/acs.macromol.9b01953
Raffaele Pastore ₁ , Ciro Siviello ₂ , Francesco Greco ₁ , Domenico Larobina ₂

Affiliation

We investigate macromolecular physical gels (strontium alginates) in a wide range of aging times and length scales by combining linear stress relaxation and dynamic light scattering (DLS) experiments. Stress relaxation shows an early logarithmic decay followed by a stretched exponential behavior, leading to define two characteristic times, which increase as distinct power laws of gel age. The DLS clearly displays anomalous microscopic dynamics, with compressed exponential decay of autocorrelation functions and ballistic wavelength dependence of the decay time. Thus, our results demonstrate that stretched stress relaxation can coexist with compressed intensity autocorrelation functions. In addition, comparison between rheology and DLS allows for the identification of two characteristic lengths that we interpret as the typical size of collapsing pores in the gel and of avalanche-like rearrangements. We discuss this scenario in terms of some recently proposed ideas on anomalous aging, such as ultralong-ranged dynamical correlations in closely athermal systems.

中文翻译：

大分子物理凝胶的反常老化和应力松弛：海藻酸锶

通过结合线性应力松弛和动态光散射（DLS）实验，我们研究了大范围的老化时间和长度范围内的大分子物理凝胶（藻酸锶）。应力松弛显示出早期的对数衰减，随后是拉伸的指数行为，从而导致定义了两个特征时间，并随着凝胶年龄的不同幂律而增加。DLS清楚地显示出异常的微观动力学，具有自相关函数的压缩指数衰减和衰减时间的弹道波长依赖性。因此，我们的结果表明，拉伸应力松弛可以与压缩强度自相关函数共存。此外，流变学和DLS之间的比较可以确定两个特征长度，我们将其解释为凝胶中塌陷孔的典型大小和雪崩样重排的典型大小。我们根据一些最近提出的关于异常老化的想法来讨论这种情况，例如紧密无热系统中的超远程动态相关性。

更新日期：2020-01-10

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