Determining the Molecular Factors that Contribute to Nanoemulsion Formation and Stabilization by Carboxylic Acid Surfactants and Polymers

在这个由化学系大分子、超分子和纳米化学计划资助的项目中，俄勒冈大学化学系的Geraldine L.Richmond教授正在研究有助于纳米乳液形成和表面活性剂和聚合物稳定的分子因素。纳米乳液是一种胶体混合物，其中一种成分作为微小颗粒悬浮在另一种物质中。牛奶是胶体的一个例子，因为细小的乳脂颗粒分散在水状液体中。胶体为广泛的生物、医学和技术应用提供了令人兴奋的机会。在这些应用中，胶体通常由油滴组成，这些油滴在水溶液中由表面吸附的两亲分子(具有亲水和亲脂特性的化合物)稳定。它们的微小直径使它们可以作为运输各种化合物的载体，这些化合物被封装在它们的内部。在这项研究中，科学家试图了解表面活性剂和聚合物在独特尺寸的球形液滴上的表面吸附和组装所需的力和能量。使用一些复杂的测量技术来研究这些体系的分子水平特征。与这项研究相关的知识有可能对药物输送、食品科学、石油回收和材料化学产生影响。研究小组正在通过针对不同年龄和人口的教育宣传努力，扩大他们的研究的影响。这些活动包括为学生和公众提供公开演示和在线视频，主题包括日常生活中的乳剂、制造和理解乳剂的简单实验、化学中的激光以及纳米乳剂的特殊性质。通过“水第一！”将研究课程融入到外展、网络和教育活动中。项目。该项目涉及与参与水研究、教育和政策的非洲女科学家合作和合作。研究小组正在详细描绘纳米液滴表面的分子特征，这些分子特征有助于通过表面吸附的烷基表面活性剂和聚合物形成和稳定纳米液滴。主要目标有两个。首先，他们想要充分表征乳化剂、油和水在动力学稳定状态下通过超声制备的纳米液滴表面的分子键、结构和取向。科学家们还将这些结果与对这些乳化剂及其对处于热力学稳定状态的平面油水界面上的油和水界面的影响的类似研究进行了比较。为这些模型研究选择的乳化剂是含有烷基表面活性剂的羧酸和聚合物。这些基础研究旨在利用这些弱酸性烷基表面活性剂和聚电解质的吸附性能，它们的表面电荷和吸附特性可以通过pH、离子强度和金属离子络合作用来改变。涉及吸附体长度、大小、疏水性和刚性变化的研究提供了与表面堆积、构象有序性和多层形成相关的额外信息。众所周知，表面电荷和空间效应都是减少这些纳米液滴聚合和相分离途径的重要因素。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Geraldine L. Richmond of the Department of Chemistry at University of Oregon, Eugene is studying molecular factors that contribute to nanoemulsion formation and stabilization by surfactants and polymers. Nanoemulsions are a class of colloids - mixture where a one component is suspended as tiny particles in another substance. Milk is an example of a colloid as small butterfat particles are dispersed in a watery liquid. Colloids provide exciting opportunities for a wide range of biological, medicinal, and technological applications. In these applications, colloids typically consist of oil-droplets that are stabilized in water solution by surface-adsorbed amphiphiles (compounds with water-loving and fat-loving properties). Their tiny diameters allow them to serve as vehicles for a wide range of compounds that are encapsulated in their interiors. In this research, scientists seek to understand the forces and energy required for surface adsorption and assembly of surfactants and polymers on spherical droplets of unique size. Molecular-level characteristics of these systems are investigated using a number of sophisticated measurement techniques. Knowledge associated with this research has the potential to impact drug delivery, food science, oil recovery and materials chemistry. The research team is broadening the impact of their research through educational outreach efforts aimed at a variety of ages and populations. The activities include public presentations and on-line videos for students and the general public on topics such as emulsions in our everyday lives, simple experiments in making and understanding emulsions, lasers in chemistry, and the special properties of nanoemulsions. Research lessons are incorporated into the outreach, networking, and educational activities through the "Water First!" project. This project involves working and collaborating with women scientists in Africa that are involved in water research, education and policy.The research team is developing a detailed picture of the molecular characteristics of the nanodroplet surface that contribute to their formation and stabilization by surface adsorbed alkyl surfactants and polymers. The main objectives is twofold. First they want to fully characterize the molecular bonding, structure and orientation of emulsifying agents, oil and water at the surface of nanodroplets prepared in their kinetically stable state by ultrasonification. The scientists also compare the results with analogous studies of these emulsifying agents and their effect on interfacial oil and water at a planar oil-water interface that is in a thermodynamically stable state. The emulsifying agents chosen for these model studies are carboxylic acid containing alkyl surfactants and polymers. These fundamental studies are designed to take advantage of the adsorptive properties of these weakly acidic alkyl surfactants and polyelectrolytes whose surface charge and adsorptive characteristics can be varied by pH, ionic strength and metal ion complexation. Studies that involve the variation in length, size, hydrophobicity and rigidity of the adsorbates provide additional information related to surface packing, conformational ordering, and multi-layer formation. Both surface charge and steric effects are known to be important factors in reducing the pathway of these nanodroplets to coalesce and phase separate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.