Pflaumbaum Manuela, Rehage Heinz
Institute of Physical Chemistry, University of Duisburg-Essen, Universitätsstr. 3-5, 45127 Essen, Germany.
Chemphyschem. 2003 Jul 14;4(7):705-13. doi: 10.1002/cphc.200200585.
Aqueous surfactant solutions of entangled, rod-shaped micelles are often characterized by monoexponential stress-relaxation processes. This special phenomenon leads to relatively simple theoretical descriptions, and viscoelastic surfactant solutions can, therefore, also be used as simple model systems for studying fundamental principles of flow. Herein, we present a detailed study of the nonlinear rheological properties of aqueous myristyl dimethylamine oxide surfactant solutions. In the regime of small deformations, shear stresses, or shear rates, the dynamic features of the viscoelastic solutions are characterized by the simple equations of a Maxwell material. At elevated values of shear stresses or deformations, however, this simple model fails and nonlinear features, such as normal stresses, stress overshoots, or shear-thinning properties occur. All these phenomena can be described by a Maxwell-type differential constitutive equation, which was first proposed by Giesekus. It turns out that the experimental results are in fairly good agreement with the theoretical predictions, if the anisotropy factor alpha is equal to 0.5. Besides transient data and nonlinear steady-state measurements, many semiempirical laws, such as the Cox-Merz rule, the Yamamoto relation, the Laun equation, and the Gleissble mirror relationships are approximately satisfied. The dynamic properties discussed in this paper are of general importance and they are equally observed in different materials such as polymer, dye, or protein solutions.
缠结的棒状胶束的水性表面活性剂溶液通常具有单指数应力松弛过程的特征。这种特殊现象导致了相对简单的理论描述，因此，粘弹性表面活性剂溶液也可以用作研究流动基本原理的简单模型系统。在此，我们对肉豆蔻基二甲基氧化胺表面活性剂水溶液的非线性流变特性进行了详细研究。在小变形、剪切应力或剪切速率范围内，粘弹性溶液的动态特性由麦克斯韦材料的简单方程表征。然而，在较高的剪切应力或变形值下，这个简单模型失效，会出现诸如法向应力、应力超调或剪切变稀特性等非线性特征。所有这些现象都可以用吉泽库斯首次提出的麦克斯韦型微分本构方程来描述。结果表明，如果各向异性因子α等于0.5，实验结果与理论预测相当吻合。除了瞬态数据和非线性稳态测量外，许多半经验定律，如考克斯 - 默茨规则、山本关系、劳恩方程和格莱斯布尔镜关系也大致得到满足。本文讨论的动态特性具有普遍重要性，并且在不同材料如聚合物、染料或蛋白质溶液中也同样观察到。
