Porpora G, Rusciano F, Guida V, Greco F, Pastore R
Department of Chemical, Materials and Production Engineering, University of Naples Federico II, P.le Tecchio 80, Naples 80125, Italy.
The Procter and Gamble Company, Brussels Innovation Center, 1853 Strombeek Bever Temselaan 100, 1853 Grimbergen, Belgium.
J Phys Condens Matter. 2021 Mar 10;33(10):104001. doi: 10.1088/1361-648X/abce6f.
Suspensions of charged vesicles in water with added salt are widespread in nature and industrial production. Here we investigate, via Brownian dynamics simulations, a model that grasps the key features of these systems, with bidisperse colloidal beads interacting via a hard-core and an electrostatic double layer potential. Our goal is to focus on a set of interaction parameters that is not generic but measured in recent experiments, and relevant for a class of consumer products, such as liquid fabric softeners. On increasing the volume fraction in a range relevant to real formulation, we show that the dynamics become progressively slower and heterogeneous, displaying the typical signatures of an approaching glass transition. On lowering the salt concentration, which corresponds to increasing the strength and range of the electrostatic repulsion, the emergence of glassy dynamics becomes significantly steeper, and, remarkably, occurs at volume fractions well below the hard-sphere glass transition. The volume fraction dependence of the structural relaxation time at different salt concentration is well described through a functional law inspired by a recently proposed model (Krausser et al 2015 Proc. Natl Acad. Sci. USA 112 13762). According to our results, the investigated system may be thought of as a Wigner glass, i.e. a low-density glassy state stabilized by long-range repulsive interactions. Overall, our study suggests that glassy dynamics plays an important role in controlling the stability of these suspensions.
添加了盐的带电囊泡在水中的悬浮液在自然界和工业生产中广泛存在。在此，我们通过布朗动力学模拟研究了一个抓住这些系统关键特征的模型，其中双分散胶体颗粒通过硬核和静电双层势相互作用。我们的目标聚焦于一组并非通用而是在近期实验中测量得到的、与一类消费品（如液体织物柔软剂）相关的相互作用参数。在增加与实际配方相关范围内的体积分数时，我们发现动力学变得逐渐缓慢且不均匀，呈现出接近玻璃化转变的典型特征。在降低盐浓度时，这相当于增加静电排斥的强度和范围，玻璃态动力学的出现变得显著更陡峭，而且值得注意的是，发生在远低于硬球玻璃化转变的体积分数处。通过受最近提出的一个模型（Krausser等人，《美国国家科学院院刊》2015年第112卷，第13762页）启发的函数定律，可以很好地描述不同盐浓度下结构弛豫时间对体积分数的依赖性。根据我们的结果，所研究的系统可被视为维格纳玻璃，即一种由长程排斥相互作用稳定的低密度玻璃态。总体而言，我们的研究表明玻璃态动力学在控制这些悬浮液的稳定性方面起着重要作用。
