Time–connectivity superposition and the gel/glass duality of weak colloidal gels
Time–connectivity superposition and the gel/glass duality of weak colloidal gels
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时间-连通性叠加和弱胶体凝胶的凝胶/玻璃二象性
DOI：
10.1073/pnas.2022339118
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
A. Poulesquen
中科院分区：
文献类型：
--
作者：
B. Keshavarz;Donatien Gomes Rodrigues;J. Champenois;Matthew G. Frith;J. Ilavsky;M. Geri;T. Divoux;G. McKinley;A. Poulesquen
意义 由于这些糊状材料不断老化的性质，量化弱胶体凝胶的粘弹性仍然具有挑战性。通过时间分辨力学和结构光谱以及时间连通性叠加原理的应用，我们构建了这些凝胶在八个十年的有效材料时间内的粘弹性模量。该协议揭示了弛豫时间谱的双重性质，分别在大尺度和小尺度上具有凝胶和玻璃状特征。临界凝胶点处的网络结构决定了弛豫光谱的基本形状，老化材料将其保留为固定骨架。观察到的非遍历行为表明，团簇的局部捕获从小尺度开始，并不断向更大尺度演化。胶体凝胶是由悬浮在溶剂中的布朗颗粒聚集而成。凝胶化是由单个颗粒之间的吸引相互作用引起的，驱动簇的形成，簇又聚集形成跨空间结构。我们通过时间分辨结构和力学光谱研究了硅铝酸盐胶体凝胶中的这一过程。利用时间连通性叠加原理，通过应用指数线性调频协议在整个凝胶过程中测量一系列快速获取的线性粘弹性光谱，将其重新调整到通用主曲线上，该主曲线以降低的频率跨越八个数量级。该分析表明，胶体凝胶的基本弛豫时间谱在时间上是对称的，具有幂律尾部，其特征在于在凝胶点设置的单个指数。微观结构力学网络具有双重特征；在短长度尺度和快速时间下，它呈现玻璃状，而在较长时间和较大尺度下，它呈凝胶状。这些结果可以通过简单的三参数本构模型来捕获，并证明成熟胶体凝胶的微观结构具有在凝胶点处创建的原始样品跨越网络的残余骨架。我们的结论通过将相同的技术应用于另一种由有吸引力的二氧化硅纳米粒子组成的众所周知的胶体凝胶系统而得到证实。结果说明了此类软玻璃材料的时间连通性叠加原理的力量，并为弱胶体凝胶的二分粘弹性性质提供了简洁的描述。
Significance Quantifying the viscoelastic properties of weak colloidal gels remains challenging due to the continuously aging nature of these pasty materials. Through time-resolved mechanical and structural spectroscopy and application of the time–connectivity superposition principle we construct the viscoelastic moduli of these gels over eight decades of effective material time. This protocol reveals the dual nature of the relaxation time spectrum with gel- and glass-like characteristics at large and small scales, respectively. The structure of the network at the critical gel point sets the underlying shape of the relaxation spectrum, which the aging material retains as a fixed skeleton. The observed nonergodic behavior suggests that the local arrest of clusters initiates from small scales and continuously evolves toward larger ones. Colloidal gels result from the aggregation of Brownian particles suspended in a solvent. Gelation is induced by attractive interactions between individual particles that drive the formation of clusters, which in turn aggregate to form a space-spanning structure. We study this process in aluminosilicate colloidal gels through time-resolved structural and mechanical spectroscopy. Using the time–connectivity superposition principle a series of rapidly acquired linear viscoelastic spectra, measured throughout the gelation process by applying an exponential chirp protocol, are rescaled onto a universal master curve that spans over eight orders of magnitude in reduced frequency. This analysis reveals that the underlying relaxation time spectrum of the colloidal gel is symmetric in time with power-law tails characterized by a single exponent that is set at the gel point. The microstructural mechanical network has a dual character; at short length scales and fast times it appears glassy, whereas at longer times and larger scales it is gel-like. These results can be captured by a simple three-parameter constitutive model and demonstrate that the microstructure of a mature colloidal gel bears the residual skeleton of the original sample-spanning network that is created at the gel point. Our conclusions are confirmed by applying the same technique to another well-known colloidal gel system composed of attractive silica nanoparticles. The results illustrate the power of the time–connectivity superposition principle for this class of soft glassy materials and provide a compact description for the dichotomous viscoelastic nature of weak colloidal gels.
影响因子：
8.6
作者：
Larsen, Travis H.;Furst, Eric M.
通讯作者：
Furst, Eric M.
软玻璃老化的线性粘弹性分析
影响因子：
3.3
作者：
Shukla, Asheesh;Shanbhag, Sachin;Joshi, Yogesh M.
通讯作者：
Joshi, Yogesh M.