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arXiv 2603.11366cond-mat.soft
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带电棒状胶体的凝胶动力学:临界行为和时间连通性叠加原理

Gelation dynamics of charged colloidal rods: critical behaviour and time-connectivity superposition principle

ENSL, CNRS, Laboratoire de Physique(里昂高等师范学院,法国国家科学研究中心,物理实验室);Institut Universitaire de France(法兰西学院)

Lise Morlet-Decarnin, Thibaut Divoux, Sebastien Manneville

AI总结:

研究揭示了高电荷棒状胶体的凝胶化机制,通过分析机械恢复动力学和临界行为,发现时间连通性叠加原理和非普遍动态指数。

摘要:

带电胶体粒子在加入盐类后,可通过静电排斥的屏蔽作用自组装成凝胶网络。尽管球形胶体的凝胶化已广泛研究,但对各向异性胶体的凝胶动力学了解较少。本文聚焦于纤维素纳米晶(CNCs)作为典型的刚性、高电荷棒状胶体。在水溶液中加入盐后,CNCs表现出从低固含量下的凝胶到高浓度下的玻璃态的丰富相图。在之前的研究所述基础上,我们对CNC悬浮液在强剪切后的机械恢复动力学进行了深入研究。时间分辨机械光谱揭示了液到固的转变,其特征为明确的临界凝胶点。随时间变化的粘弹性光谱可重新缩放至主曲线,展示了时间连通性叠加原理和临界动力学,涵盖凝胶点两侧。通过改变CNC质量分数和盐浓度,我们识别了凝胶与吸引玻璃态之间的边界,其特征为粘弹性可观测量的明显变化,包括凝胶点处的弹性与粘性模量及其高频幂律指数。动态临界指数和超扩展性分析揭示了凝胶前和凝胶后动力学的显著不对称性以及非普遍的动态指数。这些发现突显了高电荷棒状胶体特有的凝胶化机制,并呼吁进行互补的微观结构表征和理论建模。

英文摘要:

Charged colloidal particles can self-assemble into gel networks upon screening of electrostatic repulsion by added salt. While gelation of spherical colloids has been extensively studied, much less is known about the gelation dynamics of anisotropic colloids. Here, we focus on cellulose nanocrystals (CNCs) as prototypical rigid, highly charged rod-like colloids. In aqueous solution with salt, CNCs display a rich phase diagram ranging from gel at low solid content to glassy phases at higher concentrations. Building on our previous work [Morlet-Decarnin et al., ACS Macro Lett., 2023, 12, 1733], we present an extensive study of the mechanical recovery dynamics of CNC suspensions following a strong shear. Time-resolved mechanical spectroscopy reveals a liquid-to-solid transition characterized by a well-defined critical gel point. The evolving viscoelastic spectra can be rescaled onto master curves, demonstrating a time-connectivity superposition principle and critical dynamics on both sides of the gel point. By varying the CNC weight fraction and salt concentration, we identify a boundary between gel and attractive glass states marked by clear changes in rheological observables, including the elastic and viscous moduli at the gel point and their high-frequency power-law exponents. Analysis of dynamic critical exponents and hyperscaling reveals pronounced asymmetry between pre-gel and post-gel dynamics and non-universal values of the dynamic exponent. These findings highlight gelation mechanisms specific to highly charged rod-like colloids and call for complementary microstructural characterization and theoretical modeling.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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