Center for Molecular and Engineering Thermodynamics, Department of Chemical Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, USA.
Langmuir. 2010 Jun 1;26(11):8049-60. doi: 10.1021/la100026d.
We present a systematic study of thermodynamics, structure, and rheology of mixtures of cationic wormlike micelles and like-charged nanoparticles. Structural and thermodynamic measurements in dilute surfactant-nanoparticle mixtures show the formation of micelle-nanoparticle junctions that act as physical cross-links between micelles. The presence of these junctions is shown to build significant viscosity and viscoelasticity in dilute and semidilute WLMs, even in cases where the fluid is Newtonian in the absence of nanoparticles. Increases in viscosity, shear modulus, and relaxation time, as well as decreases in entanglement concentration, are observed with increasing particle concentration. As such, nanoparticle addition gives rise to a so-called "double network" comprised of micellar entanglements and particle junctions. A simple model for such networks is proposed, where the elasticity can be tuned through two energetic scales, the micellar end-cap energy and micelle-nanoparticle adsorption energy. As a practical application, the results demonstrate that nanoparticle addition provides formulators a unique method to tailor surfactant solution rheology over a wide range of conditions.
我们对阳离子蠕虫状胶束和同电荷纳米粒子混合物的热力学、结构和流变学进行了系统研究。在稀释的表面活性剂-纳米粒子混合物中的结构和热力学测量表明，形成了胶束-纳米粒子连接点，这些连接点充当了胶束之间的物理交联。事实证明，这些连接点在稀的和半稀的 WLMs 中会产生显著的黏度和黏弹性，即使在没有纳米粒子的情况下，流体在牛顿流体中也是如此。随着粒子浓度的增加，观察到黏度、剪切模量和松弛时间的增加，以及缠结浓度的降低。因此，纳米粒子的添加导致了一种所谓的“双网络”，由胶束缠结和粒子连接点组成。提出了一种用于此类网络的简单模型，其中弹性可以通过两个能量尺度来调节，即胶束端帽能量和胶束-纳米粒子吸附能量。作为实际应用，结果表明，纳米粒子的添加为配方设计师提供了一种独特的方法，可以在广泛的条件下调整表面活性剂溶液的流变性。
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