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arXiv 0908.2338cond-mat.soft
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溶剂介导的模型胶体和界面间的相互作用:微观方法

Solvent mediated interactions between model colloids and interfaces: A microscopic approach

Paul Hopkins, Andrew J. Archer, Robert Evans

摘要:

我们确定了溶剂介导的贡献的有效电位模型胶体或纳米粒子分散在一个二元溶剂,表现出流体-流体相分离。使用一个简单的密度泛函理论,我们计算的“胶体”,这被视为外部电位的存在下,这两种溶剂物种的密度分布,并确定溶剂介导(SM)的潜力。具体来说,我们计算SM电位之间(i)两个胶体,(ii)胶体和平面流体-流体界面,和(iii)胶体和平面壁与吸附润湿膜。我们考虑三种不同类型的胶体颗粒:胶体A,它喜欢的本体溶剂相丰富的物种2,胶体C,它喜欢的溶剂相丰富的物种1,和“中性”胶体B,没有强烈的偏好,任何一个阶段,即自由能插入胶体到共存的本体相几乎是相等的。当一个胶体,其中有一个优先的两种溶剂相插入到不利的相在状态点接近共存的厚吸附的“润湿”膜的优选相可能会形成周围的胶体。吸附膜的存在对SM电位的形式有着深远的影响。

英文摘要:

We determine the solvent mediated contribution to the effective potentials for model colloidal or nano- particles dispersed in a binary solvent that exhibits fluid-fluid phase separation. Using a simple density functional theory we calculate the density profiles of both solvent species in the presence of the `colloids', which are treated as external potentials, and determine the solvent mediated (SM) potentials. Specifically, we calculate SM potentials between (i) two colloids, (ii) a colloid and a planar fluid-fluid interface, and (iii) a colloid and a planar wall with an adsorbed wetting film. We consider three different types of colloidal particles: colloid A which prefers the bulk solvent phase rich in species 2, colloid C which prefers the solvent phase rich in species 1, and `neutral' colloid B which has no strong preference for either phase, i.e. the free energies to insert the colloid into either of the coexisting bulk phases are almost equal. When a colloid which has a preference for one of the two solvent phases is inserted into the disfavored phase at statepoints close to coexistence a thick adsorbed `wetting' film of the preferred phase may form around the colloids. The presence of the adsorbed film has a profound influence on the form of the SM potentials.

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