Effects of Dispersant Molecular Structure on the Stabilization of Dispersions Against Agglomeration and Sedimentation

许多工业上重要的过程都涉及到液体中的颗粒悬浮液。这些过程往往受到颗粒团聚和团聚体沉降的阻碍。工艺工程师通过添加表面活性剂（一种降低两种液体之间或液体与固体之间的表面张力的化合物）来防止颗粒聚集和沉淀，这种化合物可以覆盖颗粒并抑制它们的聚集。然而，添加表面活性剂也会改变悬浮液的总体性质，使其更难加工。本课题旨在研究在不显著改变悬浮液流动特性的前提下，防止结块和沉降的替代方法。我们的想法是找到表面活性剂，这些表面活性剂可以在液体中自发形成分子结构或组装，从而防止颗粒聚集、沉淀或两者兼而有之。研究人员正在研究一系列表面活性剂颗粒系统，并确定该系统防止团聚的特性。研究结果将有助于油漆和油墨、制药和化妆品等工业领域的工艺工程师设计出长期保持稳定并保持其有益特性的产品。该项目还涉及所有学术水平的学生，包括高中生，特别是那些来自传统上代表性不足的群体的学生，他们通过普渡大学的SEED项目被招募参与该项目。本课题的目的是筛选、评价和选择表面活性剂分散剂，以控制悬浮颗粒的团聚和沉降。表面活性剂的分子结构在胶束和囊泡等组件的形成中所起的作用，可以抑制颗粒的团聚和沉降。目前正在研究一系列广泛的表面活性剂，包括连接单极和双极头基的单极和双极碳氢化合物链。目前正在研究碳链长度为8 ~ 16的阴离子、阳离子和非离子表面活性剂。颗粒的特性，如大小、组成、密度和浓度也在研究范围内。用动态光散射和光谱比浊法测定团聚体大小，用恒应力流变仪测量流变特性的变化。低温透射电镜在适当的时候被用来表征囊泡和粒子结构。利用布朗动力学和随机动力学模拟的计算研究正在进行，以确定悬架稳定的机制。

Many industrially important processes involve suspensions of particles in a liquid. These processes are often hampered by agglomeration of the particles and sedimentation of the aggregates. Process engineers take steps to prevent agglomeration and sedimentation by adding surfactants, compounds that lower the surface tension between two liquids or between a liquid and a solid, that coat the particles and inhibit their agglomeration. However, adding a surfactant can also change the bulk properties of the suspension and make it more difficult to process. This research project involves studying and alternative approach to preventing agglomeration and sedimentation without changing significantly the flow properties of the suspension. The idea is to find surfactants that spontaneously form molecular structures or assemblies in the liquid that prevent particle agglomeration, sedimentation, or both. The researchers are examining a broad array of surfactant-particle systems and determining the characteristics of the system that prevent agglomeration. The results will help enable process engineers in such industrial areas as paints and inks, pharmaceuticals, and cosmetics to design products that remain stable and maintain their beneficial properties over long periods of time. The project also involves students at all academic levels, including high school students, especially those from traditionally underrepresented groups, who are being recruited to participate in the project through Purdue's SEED program. The goal of this project is to screen, evaluate, and select surfactant dispersants for controlling agglomeration and sedimentation of suspended particles. The role of surfactant molecular structure on the formation of assemblies such as micelles and vesicles that can inhibit agglomeration and sedimentation of particles is being investigated. A broad array of surfactants are being examined including single and double hydrocarbon chains connected to single and double polar head groups. Anionic, cationic, and nonionic surfactants with carbon chain lengths from 8 to 16 are being studied. Characteristics of the particles, such as size, composition, density and concentration, is also being included in the study. Agglomerate size is being determined by dynamic light scattering and spectroturbidimetry, and changes in rheological properties are being measured using a constant stress rheometer. Cryo-transmission electron microscopy is being used when appropriate to characterize vesicle and particle structures. Computational studies using Brownian Dynamics and Stochastic Dynamics simulations are being carried out to identify mechanisms of suspension stabilization.