Interfaces and dynamics in complex fluids: non-additive mixtures

胶体分散体是由尺寸在1纳米到1微米之间的介观粒子分散在液体中的复杂流体。有各种各样的不同类型的颗粒，具有不同的形状、大小、电荷、表面和介电性质，以及相当范围的不同类型的溶剂，包括水和非水，其中还包括添加剂，如盐或贫化剂。胶体分散的日常例子包括乳胶、血液和油漆。除了具有许多重要的工业应用外，表征良好的合成胶体分散体是研究凝聚物质中各种基本的体相、界面和动力学现象的重要模型系统。这两个物种都被建模为坚硬的球体；然而，不同的球体对之间的交叉相互作用与人们从它们的几何形状推断的不同，即排斥发生在比单个直径的算术平均值更小或更大的距离上。这种非加性硬球模型具有有趣的性质，从液-液相分离的发生到高密度下的聚集现象。在真实的胶体分散中，由于粒子上电荷或磁偶极子的存在而发生非加性。我们将使用先前为该模型发展的密度泛函理论和计算机模拟来研究非可加硬球模型的各种相关的界面和动力学现象。我们的目的是深入了解支配该模型的长度尺度的竞争如何影响自由液-液界面的性质、壁上和毛细管中的吸附行为、以及主体和界面上的动力学关联，以及这些界面如何响应驱动系统失衡的外场，例如与沉积动力学和暴露在剪切流中的分散体有关。

Colloidal dispersions are complex fluids of mesoscopicparticles with sizes between 1nm and 1micron that are dispersed in aliquid. There is a large variety of different types of particles withvarying shape, size, charge, surface and dielectric properties, aswell as a considerable range of different types of solvents, bothaqueous and non-aqueous, which also include additives such as salt ordepletion agents. Everyday examples of colloidal dispersions includemilk, blood, and paint. Besides possessing many important industrialapplications, well-characterized synthetic colloidal dispersions serveas important model systems to investigate a wide variety offundamental bulk, interfacial and dynamical phenomena in CondensedMatter.Here we consider a theoretical model for colloidal dispersions withtwo different types of particles. Both species are modelled as hardspheres; the cross interaction between pairs of spheres of unlikespecies is however different from what one would infer from theirgeometric shapes, i.e. the repulsion occurs at a distance that issmaller or larger than the arithmetic mean of the individualdiameters. This non-additive hard sphere model has interestingproperties ranging from the occurrence of liquid-liquid phaseseparation to clustering phenomena at high densities. In realcolloidal dispersions non-additivity occurs due to the presence ofelectrical charges or magnetic dipoles on the particles.We will investigate a wide variety of relevant interfacial anddynamical phenomena of the non-additive hard sphere model using bothour previously developed density functional theory for this model aswell as computer simulations. Our aim is to gain insight into how thecompetition of the length scales that govern this model affects theproperties of free liquid-liquid interfaces, of adsorption behaviourat walls and in capillaries, and of dynamical correlations in bulk andat interfaces, and how such interfaces respond to external fields thatdrive the system out-of-equilibrium, as is relevant e.g. in thedynamics of sedimentation and for dispersions exposed to shear flow.