NSF-BSF: Interfacial freezing and shape transformations in surfactant/particle-co-stabilized emulsions

NSF-BSF：表面活性剂/颗粒共稳定乳液中的界面冻结和形状转变

• 批准号: 2110611
• 负责人: Daeyeon Lee
• 金额: $ 36.95万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2110611&HistoricalAwards=false
• 关键词: NSF; BSF; Interfacial; freezing; shape

Emulsions are made of droplets of one liquid suspended in another, immiscible, liquid such as oil droplets suspended in water. Liquid droplets adopt spherical shapes due to surface tension. It was recently discovered that, for over 60 different chemical combinations, the surface of droplets, which is covered with molecules called surfactants, can undergo freezing, which induces drastic changes in the shape of the droplets. This interfacial freezing (IF) phenomenon leads to the formation of faceted liquid droplets, thin platelets or rod/hair-like emulsion droplets. On one hand, these shape transformations may lead to major complications in industrial processes, such as pipe clogging by hair-like droplets. On the other hand, these shape transformations provide a powerful method of synthesizing particles with complex shapes for advanced applications. In numerous industrial and natural settings, the interfaces of emulsion droplets are covered by mixtures of surfantants and solid microparticles, known as colloids. However, the influence of surface-adsorbing colloids on the IF and droplet faceting phenomena has not been extensively investigated, although such colloids are present in many real-world emulsions. The proposed work aims to understand the effect of colloids on the shape transformation of emulsion droplets undergoing IF. Developing a deep understanding of the effect of particle size, concentration, shape and surface chemistry on the shape transformation of emulsions will enable strategies to prevent deleterious impacts of such phenomena in the food, oil and gas, pharmaceutical and cosmetic industries and lead to novel synthesis techniques to create new materials.The composition, structure and elasticity of the droplet interface play a crucial role in determining the stability, encapsulation capability and processability of emulsions in industry and in common chemical and biological systems. In many emulsions, the interfacial molecular layer can undergo a freezing transition, dramatically modifying the emulsion properties. This interfacial freezing (IF) transition drastically changes the shape of the emulsion droplets for sizes spanning 13 orders of magnitude in volume, and for over 60 different oil-surfactant combinations. Such shape transitions may lead to the formation of faceted liquid objects, high aspect ratio platelets or rod/hair-like emulsion droplets, changing the flow properties of the emulsions and potentially causing gelation leading to process complications. Engineering shape transformations of droplets also provides a powerful method of synthesizing highly shape-anisotropic particles with unique functionality. In numerous industrial and natural settings, the interfaces of the emulsions are decorated by mixtures of particles and surfactants, with the particles either added intentionally for emulsion stabilization, or being present as a contaminant. This project aims at understanding the interplay between the surface-adsorbed particles and the IF phenomena, with a particular focus on the effect of isotropic and Janus particles on the shape transformations. Using particle tracking and recently developed microfluidic methods, this project will investigate the effect of wetting properties, size, shape and interfacial concentration of particles on IF-driven shape transformations of droplets. While conventional isotropic colloids may be easily expelled from a droplet interface undergoing IF due to extremely low interfacial tension, Janus particles will strongly adsorb to such an interface due to their intrinsic surface activity, potentially enabling control over the shape transformation. New methods to control the IF-driven self-shaping of droplets will have a potentially transformative impact for oil and gas, pharmaceutical, food, agricultural and cosmetics industries, where emulsions are frequently exposed to surfactant- and particle-containing media. A new demonstration illustrating the interplay between the interfacial curvature and crystallization will be developed by undergraduate and graduate students for local high school teachers and students. To broaden participation of students from underrepresented groups, students with diverse backgrounds will be recruited by hosting students from the University of Puerto Rico-Humacao and by collaborating with Advancing Women in Engineering and Louise-Stoke Alliance for Minority Participation programs.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.

乳液由一种液体的液滴制成，该液体悬浮在另一种液体中，例如悬浮在水中的油滴。 液滴由于表面张力而采用球形形状。 最近发现，对于60多种不同的化学组合，液滴的表面被称为表面活性剂的分子覆盖，可以冻结，从而引起液滴形状的急剧变化。这种界面冻结（如果）现象会导致刻面液滴，薄血小板或杆/头发样乳液液滴形成。一方面，这些形状转化可能会导致工业过程的重大并发症，例如被头发状液滴堵塞的管道。另一方面，这些形状转换提供了一种有力的方法，可以使粒子具有用于高级应用的复杂形状。在许多工业和自然环境中，乳液液滴的界面被表面和固体微粒（称为胶体）的混合物覆盖。然而，尽管在许多现实世界中存在这种胶体，但尚未对表面吸附胶体对IF和液滴刻面现象的影响。提出的工作旨在了解胶体对经过IF的乳液液滴的形状转化的影响。 深入了解粒度，浓度，形状和表面化学对乳液形状转化的影响，将使策略能够防止这种现象在食品，石油和天然气，药物和天然气，药物和化妆品工业中的有害影响在工业和普通化学和生物系统中。在许多乳液中，界面分子层可以进行冰冻过渡，从而大大改变乳液的特性。这种界面冻结（如果）过渡会大大改变尺寸涵盖13个数量级的乳液液滴的形状，以及超过60多种不同的油性表面活性剂组合。这种形状的转变可能导致形成相的液体物体，高纵横比血小板或杆/头发样乳液液滴，改变乳液的流动性能并可能导致凝胶化导致过程并发症。液滴的工程形状转换还提供了一种具有独特功能的高度形状 - 异位粒子颗粒的强大方法。在众多工业和自然环境中，乳液的界面是由颗粒和表面活性剂的混合物装饰的，颗粒要么有意添加以进行乳液稳定，要么以污染物为污染物。该项目旨在理解表面吸附的粒子与IF现象之间的相互作用，并特别关注各向同性和Janus颗粒对形状转化的影响。使用粒子跟踪和最近开发的微流体方法，该项目将研究颗粒的润湿性能，大小，形状和界面浓度对液滴的IF驱动形状转换的影响。尽管由于极低的界面张力，但常规的各向同性胶体可能很容易从液滴界面中排出，但由于其内在的表面活性，Janus颗粒将强烈吸附到这种界面上，从而有可能控制形状转化。控制液滴的IF驱动自变形的新方法将对石油和天然气，药物，食物，农业和化妆品行业产生潜在的变革影响，在这些方法中，乳液经常暴露于表面活性剂和含粒子的培养基中。一个新的演示说明了界面曲率和结晶之间的相互作用，将由本科生和研究生为当地的高中老师和学生开发。 To broaden participation of students from underrepresented groups, students with diverse backgrounds will be recruited by hosting students from the University of Puerto Rico-Humacao and by collaborating with Advancing Women in Engineering and Louise-Stoke Alliance for Minority Participation programs.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.

项目成果

Salt-induced stability and modified interfacial energetics in self-faceting emulsion droplets

自面乳液液滴中盐诱导的稳定性和改进的界面能量学

• DOI: 10.1016/j.jcis.2022.03.146
• 发表时间: 2022
• 期刊: Journal of Colloid and Interface Science
• 影响因子: 9.9
• 作者: Nanikashvili, Pilkhaz M.;Butenko, Alexander V.;Deutsch, Moshe;Lee, Daeyeon;Sloutskin, Eli
• 通讯作者: Sloutskin, Eli