Pickering Emulsions - A Paradigm Shift

摘要：乳液在自然和工业过程中无处不在。传统乳剂使用有机表面活性剂或聚合物作为稳定剂。虽然固体颗粒稳定乳状液（Pickering乳状液）在原油回收、原油分离清洗、废水处理中经常遇到，但人们对这一现象的认识甚少，近一个世纪以来一直被忽视。迫切需要新的专家来满足我国在这一研究领域的需要。本建议著重于整合皮克林乳剂的研究与教育。利用激光扫描共聚焦显微镜和环境透射电子显微镜（ETEM）研究了皮克林乳状液中微、纳米级固体颗粒的自组装。对于含有微颗粒的皮克林乳液，我们将研究固体颗粒浓度、颗粒大小、颗粒润湿性和体粘度对自组装的影响。我们还将测试Langmuir吸附模型的适用性。对于含有纳米颗粒的皮克林乳液，我们将研究纳米颗粒在乳液界面上的结构（单层或多层，有序或随机排列等），并将实验结果与微观非连续介质模型进行比较。此外，我们将研究微粒子在乳液界面上的迁移率，特别是界面曲率对单粒子运动和多粒子团簇迁移率的影响。皮克林乳剂提供了一个胶体科学的新范式，提出的工作预计将有助于更好地理解皮克林乳剂的形成。由于皮克林乳液为固体颗粒的自组装提供了一种新颖而简单的模板，因此所提出的工作也有助于研究固体颗粒在液/液界面上自组装的潜在机制。皮克林乳剂也可以作为模型系统来研究二维固体颗粒的扩散、迁移和原位结构形成。此外，PI小组的初步工作提供了第一个使用ETEM技术在液体介质中成像纳米颗粒的工作，以及第一个揭示在液体/液体界面上自组装纳米颗粒的详细结构的工作，当纳米颗粒的大小与液体的分子尺寸相当时。利用电瞬变电磁法的后续研究将对纳米粒子科学技术产生重大影响。更广泛的影响（外在优点）研究与教育的整合将实现NSF的战略成果目标：人、思想和工具。基于对教育的坚定承诺，PI将在现有课程中建立与研究相关的开放式项目，促进本科生和研究生的研究，建立一个新的暑期项目以扩大代表性不足群体的参与，在大学预科工程学院担任导师，并促进技术转让。皮克林乳剂涉及颗粒使用的创新概念；预计拟议的工作将为广泛的实际应用提供新的机会，并将成为以促进经济增长和提高生活质量的方式将智力资本和新兴技术结合在一起的杰出范例。预计它还将对石油开采产生重大影响，这将对环境的恢复和保护作出重大贡献。最后，但并非最不重要的是，这个项目也提供了一个独特的机会，以满足我们国家对尖端研究的迫切需求，在21世纪具有不可思议的扩展潜力。

ABSTRACT - 0500323Texas Tech UniversityEmulsions are ubiquitous in natural and industrial processes. Conventional emulsions use organic surfactants or polymers as stabilizers. Although solid particle stabilized emulsions (Pickering emulsions) are often encountered in the recovery of crude oil, oil separation and cleaning, and wastewater treatment, the phenomenon is poorly understood and has been neglected for nearly a century. There is a critical call for new experts to meet our nation's need in this research area.This proposal focuses on integrating research and education centering on Pickering emulsions. Self-assembly of micro-sized and nano-sized solid particles in Pickering emulsions will be investigated using a laser scanning co focal microscope and an environmental transmission electron microscope (ETEM). For Pickering emulsions containing microparticles, we will investigate the influence of solid particle concentration, particle size, particle wettability, and bulk viscosity on self-assembly. We will also test the applicability of the Langmuir adsorption model. For Pickering emulsions containing nanoparticles, we will investigate the structure of nanoparticles (monolayer or multilayer, ordered or randomly packed, etc.) at the emulsion interface and compare experimental results to a microscopic noncontinuum model. In addition, we will investigate the mobility of microparticles at emulsion interfaces, in particular the influence of interface curvature on the single particle movement and the mobility of multi-particle clusters.Pickering emulsions offer a new paradigm of colloidal science, and the proposed work is anticipated to contribute significantly to a better fundamental understanding of the formation of Pickering emulsions. The proposed work also contributes to the underlying mechanisms of the self assembly of solid particles at liquid/liquid interfaces since Pickering emulsions offer a novel and simple template for self-assembling solid particulates. Pickering emulsions can also serve as model systems to investigate diffusion, mobility, and in-situ structural formation of solid particles at the two dimension. In addition, the preliminary work from the PI's group offers the first work of imaging nanoparticles in a liquid medium using the ETEM technique, as well as the first work revealing the detailed structure of self-assembled nanoparticles at a liquid/liquid interface when the size of the nanoparticles is comparable to the molecular dimension of the liquids. Follow-up research using the ETEM technique will have a significant impact on nanoparticle science and technology.Broader Impacts (Extrinsic Merit) The integration between research and education will be performed to meet the NSF's goals for strategic outcomes: People, Ideas and Tools. With a strong commitment to education, the PI will establish research-related open-ended projects in the existing courses, promote undergraduate and graduate research, establish a new summer program to broaden the participation of underrepresented groups, mentor in the Pre-College Engineering Academy, and promote technology transfer. Pickering emulsions involve an innovative concept for particle use; the proposed work is anticipated to provide new opportunities for widespread practical applications and will be an outstanding example of bringing intellectual capital and emerging technologies together in ways that promote economic growth and an improved quality of life. It is also anticipated to make a meaningful impact in oil recovery, which will contribute significantly to environmental restoration and protection. Last, but not least, this project also provides a unique opportunity to meet our nation's critical need for a cutting-edge research with a potential of incredible expansion in the 21st century.