Marangoni Transport Synergism in Mixed Surfactant Systems

表面活性剂是降低两相（例如油和水）之间的表面张力的化合物，并且对于一系列复杂流体产品是重要的，例如洗衣洗涤剂、用于提高石油采收率的驱油液以及许多食品、药品和消费品。由表面张力梯度驱动的流体流动被称为“马兰戈尼流动”，并且已经在含有单一表面活性剂的系统中得到了充分的研究。然而，工业上重要的产品通常含有表面活性剂的混合物。该研究项目考虑了表面活性剂混合物如何对这些Marangoni流产生强烈的合作或协同效应。正在进行测量这些流量和界面上的表面活性剂的影响的实验，并将其与针对这些多组分系统修改的理论进行比较。在现有知识和方法的基础上，这项研究扩展到基本上有趣和商业上重要的领域。了解表面活性剂之间的相互作用对许多行业的产品配方有着潜在的强大帮助。 STEM人力资源基础设施受益于研究生和本科生的研究培训。 此外，卡内基梅隆大学的物理概念拓展项目还对中学生进行了指导，在该项目中，学生设计的实验揭示了液体商业产品配方背后的界面工程概念。马兰戈尼协同作用是在两种表面活性剂存在下，在相同的界面张力下，产生的马兰戈尼输送比单独使用两种表面活性剂时更强。这种协同作用的结果，从热力学，扩散，流动条件和动力学速率常数对马兰戈尼运输的耦合效应。该研究项目证明了这种协同作用并确定了产生这种协同作用的条件。实验重点是流过纯油层的水溶液中的双组分表面活性剂和流过含表面活性剂油膜的单表面活性剂水溶液。瞬态界面速度被测量为本体组成的变化，以驱动系统的平衡。这些传输实验正在补充平衡界面张力测量和理论传输建模，以确定动态参数对表面活性剂组合物产生Marangoni协同作用的影响。这项研究所产生的知识填补了文献中的一个重要知识空白，并为复杂流体配方提供了新的界面方法。

Surfactants are compounds that lower the surface tension between two phases (for example, oil and water) and are important for a range of complex fluid products, such as laundry detergents, flooding fluids for enhanced oil recovery, and many food, pharmaceutical and consumer products. Fluid flows driven by gradients in surface tension are called "Marangoni flows" and have been well-studied in systems containing a single surfactant. However, industrially important products typically contain mixtures of surfactants. This research project considers how surfactant mixtures may produce strong cooperative or synergistic effects on these Marangoni flows. Experiments to measure these flows and the effects of the surfactants on the interfaces are being performed and compared to theories modified for these multi-component systems. While building on existing knowledge and methods, this research expands into fundamentally interesting and commercially important areas. Understanding the interactions between surfactants is a potentially powerful aid to product formulation across a host of industries. STEM human resource infrastructure is benefitting from the research training of graduate and undergraduate students. Additionally, middle school students are being mentored through the Carnegie Mellon University Physics Concepts Outreach Program in a project in which student-designed experiments reveal interfacial engineering concepts underlying liquid commercial product formulations.Marangoni synergism is the creation of stronger Marangoni transport in the presence of two surfactants than is obtained from either of the two on their own, at the same interfacial tension. This synergism results from the coupled effects of thermodynamics, diffusion, flow conditions, and kinetic rate constants on Marangoni transport. This research project demonstrates this synergism and identifies the conditions that produce it. Experiments are focusing on two-component surfactants in aqueous solutions flowing past a pure oil layer and single-surfactant aqueous solutions flowing past a surfactant-containing oil film. Transient interfacial velocities are being measured as the bulk composition is changed to drive the system out of equilibrium. These transport experiments are being complemented by equilibrium interfacial tension measurements and theoretical transport modeling to identify the influence of dynamic parameters on surfactant compositions that yield Marangoni synergism. The knowledge generated by this research fills a significant knowledge gap in the literature and enables new interfacial approaches for complex fluid formulation.