Institut des Molécules et Matériaux du Mans (IMMM), UMR 6283 CNRS - Le Mans Université, 1, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France; Laboratoire Réactions et Génie des Procédés, UMR 7274 CNRS, Université de Lorraine, 1 rue Grandville, 54001 Nancy, France.
Laboratoire Réactions et Génie des Procédés, UMR 7274 CNRS, Université de Lorraine, 1 rue Grandville, 54001 Nancy, France.
J Colloid Interface Sci. 2022 Sep 15;622:126-134. doi: 10.1016/j.jcis.2022.04.047. Epub 2022 Apr 15.
The measurement of interfacial viscoelastic moduli provides information on the ability of surface-active agents to texture the interface. However, the contribution of the bulk rheology cannot be ignored in particular when the continuous phase exhibits a gel-like behavior, even with low modulus.
Between 2 and 6 g/L, κ-carrageenan aqueous solutions have no significant activities at interfaces. At low concentrations or high temperatures, they behave like Newtonian liquids. Upon heating or cooling, a reversible liquid/gel transition appears with a hysteresis where the rheological behavior can be easily modulated by adjusting κ-carrageenan concentration. The frequency dependence of bulk and interfacial viscoelastic moduli are determined using a conventional shear rheometer and a drop tensiometer with a polyisobutene oil, respectively.
The effect of concentration and temperature is analyzed and the frequency dependence of interfacial moduli is correlated with those of the bulk. In presence of a gelled κ-carrageenan solutions, an elastic behavior of the interface appears and strengthens as the elastic modulus of the suspended phase is high. It turns out that the oscillating pendant drop method could be a sensitive indicator of the presence of very weak gels, even hardly detected by a shear classical rheometry.
界面黏弹性模量的测量提供了有关表面活性剂使界面具有纹理能力的信息。然而，在连续相表现出凝胶状行为的情况下，特别是在模量较低的情况下，体积流变学的贡献不容忽视。
在 2 到 6 克/升之间，κ-卡拉胶水溶液在界面上没有显著的活性。在低浓度或高温下，它们表现为牛顿流体。加热或冷却时，会出现可逆的液体/凝胶转变，具有滞后性，通过调整 κ-卡拉胶浓度可以很容易地调节流变行为。使用常规剪切流变仪和聚异丁烯油的滴张力计分别确定了体积和界面黏弹性模量的频率依赖性。
分析了浓度和温度的影响，并将界面模量的频率依赖性与体积模量的频率依赖性相关联。在存在凝胶化 κ-卡拉胶溶液的情况下，界面出现弹性行为，并且随着悬浮相的弹性模量增加而增强。事实证明，振荡悬挂液滴法可能是存在非常弱凝胶的敏感指标，即使使用剪切经典流变仪也难以检测到。
