REG: Imaging of Transition-State Microstructures in Surfactant Aggregates by Time-resolved Cryogenic Transmission Electron Microscopy

REG：通过时间分辨低温透射电子显微镜对表面活性剂聚集体中的过渡态微观结构进行成像

• 批准号: 9809286
• 负责人: Arijit Bose
• 金额: $ 2万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-01 至 2001-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9809286&HistoricalAwards=false
• 关键词: REG; Imaging; Transition; State; Microstructures

ABSTRACT CTS-9809286 A. Bose/U. of Rhode Island The Department of Chemical Engineering at the University of Rhode Island will purchase an automated, pneumatically-driven mixing and microliter liquid delivery device, as well as modify our current Controlled Environment Vitrification System (CEVS) in order to image non-equilibrium microstructures in surfactant-based colloids. The experiments represent part of an ongoing investigation of the dynamics of aggregate formation and breakup in these systems. Following rapid mixing of feed solutions, the mixture will be delivered onto a holey carbon grid, then plunged past blotters into a cryogen after a controlled time delay. This will permit specimen vitrification at predetermined times after mixing, while trapping aggregates in their native states. These samples, with well-defined ages, will then be examined using cryogenic transmission electron microscopy, so that intermediate state structures can be identified directly. The proposed modification on the CEVS will give a critical and unique ability to image microstructures with a resolution of tens of milliseconds (corresponding to one of the important relaxation times in many surfactant-based systems) and higher. The experiments will enable identification of new, potentially useful, thermodynamically metastable or kinetically stable transition states. Complementary experiments using a range of other techniques, including time-resolved small angle neutron scattering and time-resolved static and dynamic light scattering will also be conducted. In conjunction with the cryo-TEM, the most complete picture of phase transition dynamics in surfactant colloidal systems to date will be able to be developed measurements will be made for a carefully selected set of single- and mixed-surfactant systems, over a range of temperatures, salt and amphiphile concentrations, and initial states. The specific roles played by surfactant chemistry, architecture and solution conditions on the kinetics of sel f-assembly will be determined. Key variables that can be used to modulate the dynamics of formation and breakup of aggregates, as well as transition-state structures, will be established. These experiments will result in a comprehensive and generic understanding of the factors that control self-assembly and breakup of surfactant aggregates, and will lay the ground work for understanding aggregation in more complex molecular systems. They will aid in the development of strategies for designing equilibrium, metastable or kinetically stable surfactant-base aggregates with lifetimes and morphologies tuned for specific applications such as encapsulation, drug delivery, contaminant removal and micellar ultrafiltration. They will also provide important data for comparison with future simulations of structural transitions and dynamics.

摘要CTS-9809286 A. Bose/U.来自罗得岛 罗得岛大学化学工程系将购买一个自动化的、气动驱动的混合和微升液体输送装置，并修改我们目前的受控环境玻璃化系统（CEVS），以便对基于表面活性剂的胶体中的非平衡微观结构进行成像。 这些实验代表了正在进行的调查，在这些系统中的聚合物形成和分解的动力学的一部分。 在进料溶液快速混合后，混合物将被输送到多孔碳网格上，然后在受控的时间延迟后通过吸墨纸投入冷冻剂中。 这将允许样品在混合后在预定时间玻璃化，同时捕获处于其天然状态的聚集体。 这些样品，具有明确的年龄，然后将使用低温透射电子显微镜检查，使中间状态的结构可以直接识别。对CEVS的拟议修改将提供一个关键的和独特的能力，以数十毫秒的分辨率（对应于许多基于表面活性剂的系统中的重要弛豫时间之一）和更高的图像微结构。 这些实验将能够识别新的、潜在有用的、化学亚稳态或动力学稳定的过渡态。 还将利用一系列其他技术进行补充实验，包括时间分辨小角中子散射和时间分辨静态和动态光散射。 结合低温透射电镜，最完整的图片在表面活性剂胶体系统的相变动力学的日期将能够开发测量将是一组精心挑选的单一和混合的表面活性剂系统，在一定的温度范围内，盐和两亲物的浓度，和初始状态。表面活性剂的化学性质，结构和溶液条件对自组装动力学的具体作用将被确定。 将建立可用于调节聚集体的形成和破裂的动力学以及过渡态结构的关键变量。 这些实验将导致控制表面活性剂聚集体的自组装和分裂的因素的全面和通用的理解，并将为理解更复杂的分子系统中的聚集奠定基础。 它们将有助于开发用于设计平衡，亚稳态或动力学稳定的表面活性剂-碱聚集体的策略，这些聚集体具有针对特定应用（如封装，药物递送，污染物去除和胶束超滤）调整的寿命和形态。 它们还将提供重要的数据，用于与未来的结构转变和动态模拟进行比较。