Department of Chemical Engineering, Faculty of Chemistry, Sofia University, 1 James Bourchier Avenue, 1164 Sofia, Bulgaria.
Langmuir. 2012 Jan 17;28(2):1115-26. doi: 10.1021/la2035517. Epub 2011 Dec 30.
We study the effect of two cationic polymers, with trade names Jaguar C13s and Merquat 100, on the rheological properties of foams stabilized with a mixture of anionic and zwitterionic surfactants (sodium lauryloxyethylene sulfate and cocoamidopropyl betaine). A series of five cosurfactants are used to compare the effect of these polymers on foaming systems with high and low surface dilatational moduli. The experiments revealed that the addition of Jaguar to the foaming solutions leads to (1) a significant increase of the foam yield stress for all systems studied, (2) the presence of consecutive maximum and minimum in the stress vs shear rate rheological curve for foams stabilized by cosurfactants with a high surface modulus (these systems cannot be described by the Herschel-Bulkley model anymore), and (3) the presence of significant foam-wall yield stress for all foaming solutions. These effects are explained with the formation of polymer bridges between the neighboring bubbles in slowly sheared foams (for inside foam friction) and between the bubbles and the confining solid wall (for foam-wall friction). Upon addition of 150 mM NaCl, the effect of Jaguar disappears. The addition of Merquat does not noticeably affect any of the foam rheological properties studied. Optical observations of foam films, formed from all these systems, show a very good correlation between the polymer bridging of the foam film surfaces and the strong polymer effect on the foam rheological properties. The obtained results demonstrate that the bubble-bubble attraction can be used for efficient control of the foam yield stress and foam-wall yield stress, without significantly affecting the viscous friction in sheared foams.
我们研究了两种阳离子聚合物，商品名为 Jaguar C13s 和 Merquat 100，对阴离子和两性离子表面活性剂（月桂酰乙氧基硫酸钠和椰油酰胺丙基甜菜碱）混合物稳定的泡沫的流变性质的影响。使用了一系列五种共溶剂来比较这些聚合物对具有高和低表面扩张模量的发泡系统的影响。实验表明，Jaguar 的添加导致（1）所有研究体系的泡沫屈服应力显著增加，（2）由表面模量高的共溶剂稳定的泡沫的应力与剪切率流变曲线中存在连续的最大和最小（这些体系不能再用赫谢尔-布尔克利模型来描述），以及（3）所有发泡溶液的泡沫壁屈服应力显著增加。这些效应可以用在缓慢剪切的泡沫中（用于内部泡沫摩擦）和在泡沫和限制固体壁之间（用于泡沫壁摩擦）形成相邻气泡之间的聚合物桥来解释。添加 150 mM NaCl 后，Jaguar 的作用消失。添加 Merquat 不会明显影响研究的任何泡沫流变性质。对所有这些体系形成的泡沫膜的光学观察表明，泡沫膜表面的聚合物桥接与聚合物对泡沫流变性质的强烈影响之间存在很好的相关性。得到的结果表明，气泡-气泡吸引力可用于有效控制泡沫屈服应力和泡沫壁屈服应力，而不会显著影响剪切泡沫中的粘性摩擦。
