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.罗德岛大学化学工程系将购买自动化、气动驱动的混合和微升液体输送装置，并修改我们当前的受控环境玻璃化系统 (CEVS)，以便对非平衡微观结构进行成像在基于表面活性剂的胶体中。 这些实验是对这些系统中聚集体形成和分解动力学正在进行的研究的一部分。 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，同时将聚集体捕获在其自然状态。 这些具有明确年龄的样本随后将使用低温透射电子显微镜进行检查，以便可以直接识别中间态结构。所提出的对 CEVS 的修改将提供关键且独特的能力，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）和更高的分辨率对微观结构进行成像。 这些实验将能够识别新的、潜在有用的、热力学亚稳态或动力学稳定的过渡态。 还将进行使用一系列其他技术的补充实验，包括时间分辨小角度中子散射和时间分辨静态和动态光散射。 与冷冻 TEM 相结合，将能够开发出迄今为止表面活性剂胶体系统中相变动力学的最完整图像。将对一组精心挑选的单一和混合表面活性剂系统进行测量，范围涵盖温度、盐和两亲物浓度以及初始状态。表面活性剂化学、结构和溶液条件对自组装动力学所起的具体作用将被确定。 将建立可用于调节聚集体形成和分解动力学以及过渡态结构的关键变量。 这些实验将使人们对控制表面活性剂聚集体自组装和分解的因素有一个全面和普遍的理解，并为理解更复杂的分子系统中的聚集奠定基础。 它们将有助于开发设计平衡、亚稳态或动力学稳定的表面活性剂基聚集体的策略，其寿命和形态可针对特定应用（如封装、药物输送、污染物去除和胶束超滤）进行调整。 他们还将提供重要数据，用于与未来的结构转变和动态模拟进行比较。