Nanoparticle ionic fluids: interactions and transport properties

CBET-0756516 ArcherIntelligence优点：基于纳米粒子的离子材料(NIMS)是康奈尔大学最近发现的一种新型杂化材料。NIMS是通过将带电低聚物共价连接到纳米颗粒表面而形成的。低聚物上的电荷被反离子物种平衡，该反离子物种可以从致密的分子实体(如氯离子)到更大的有机物种(如异构体离子)。根据成分之间的相互作用(核心颗粒、附着的低聚物和相关的反离子)，材料的物理性质可以在惊人的大范围内进行调整。光谱的一端是具有高核心颗粒含量的材料，它们显示出类似于玻璃、硬蜡和凝胶的特性。在另一个极端是自发形成均质颗粒基离子流体的体系，其特征是传输性质与由分子构建块组成的简单牛顿液体非常相似。这些纳米粒子离子液体类似于分子离子液体，因为它们能够形成具有高介电常数的零蒸汽压、绿色溶剂。然而，因为它们包含一个无机颗粒核心，所以可以访问更令人兴奋的属性阵列。这项拟议的研究采用实验、理论和计算机模拟相结合的方法来了解NIMS中的基本力，并确定这些力如何影响其传输特性。我们的初步研究表明，纳米粒子离子液体是任何大小的粒子系统的第一个例子，可以在没有溶剂的情况下达到平衡。这些研究还表明，两种新类型的相互作用对于理解我们的流体的稳定性和预测它们的传输特性是重要的：(I)由于有效溶剂与核心颗粒的附着而产生的熵吸引力；(Ii)由于表面附着的、可弯曲的偶极子在核心颗粒上产生的静电力。这是一种开放的可能性，可以基于现有的大量无机颗粒化学和形状创建全新类型的混合流体。这类流体的独特性能使其具有广泛的应用吸引力，包括高导热转印液体、喷墨可打印半导体油墨、高温电池的稳定电解液、军事和执法人员的轻型保形盔甲，以及用于光刻的高折射率液体。这些应用中的大多数是由分子构建块产生的流体无法访问的。这项拟议的研究是对控制这些类型流体的结构和性质的相互作用力的基础理解的第一次尝试。我们相信，我们的工作将为如何为许多目标应用选择组件(例如，核心颗粒大小、形状、体积分数、电晕和反离子相对分子质量以及化学)提供关键指导。此外，由于我们的流体在单一材料中结合了胶体、聚合物和复杂流体行为的元素，我们相信拟议的研究结果将有助于扩展和现代化关于胶体现象和复杂流体流动的文献。我们相信，受我们的材料影响的应用范围的一个直接结果是，对于该领域的受试者来说，在研究中发展起来的知识转移到课堂上的速度将比正常情况下更快。NIMS的新颖性及其与易于欣赏的应用的相关性也为吸引更年轻的学生(K-12)从事科学提供了新的机会。具体地说，我们将与康奈尔材料研究中心(CCMR)合作，根据材料的应用开发演示，例如喷墨可打印油墨、仿形防弹衣和用于光刻的高指数液体。我们这些演示的目标是让学生在很小的时候就从他们的基本单位或构件的角度来思考材料，并认识到物理特性和这些单位之间的力之间的联系。我们还相信，将NIMS中的流动转变与散射实验揭示的结构转变联系起来的视频演示将有助于高级学生理解复杂流体的输运性质及其相互作用之间的关系。我们将在本科生的流体力学(ChemE 323)和聚合物物理(ChemE 745)研究生课程中使用这些视频演示，并计划利用YouTube门户网站向更广泛的受众传播它们。

CBET-0756516ArcherIntellectual Merit: Nanoparticle-based ionic materials (NIMS) are a new class of hybrid materials recently discovered at Cornell. NIMS are created by covalent attachment of charged oligomers to the surface of nanoparticles. The charge on the oligomer is balanced by a counterion species that can vary from a compact molecular entity such as a chloride ion, to a more bulky organic species such as an Isosterate ion. Depending on the interactions between the components (core particles, attached oligomers, and associated counterions), physical properties of the materials can be tuned over a surprisingly wide range. On one end of the spectrum are materials with high core particle content, which display properties similar to glasses, stiff waxes, and gels. At the opposite extreme are systems that spontaneously form homogeneous particle-based ionic fluids, characterized by transport properties remarkably similar to simple Newtonian liquids comprised of molecular building-blocks. These nanoparticle ionic fluids resemble molecular ionic liquids in their ability to form zero vapor pressure, ?green?, solvents with high dielectric constants. Because they contain an inorganic particle core, however, a more exciting array of properties can be accessed. The proposed research uses a combination of experiment, theory, and computer simulations to understand the fundamental forces in NIMS and to determine how these forces influence their transport properties. Our preliminary studies indicate that nanoparticle ionic fluids are the first example of a system of particles of any size that can reach equilibrium without a solvent. These studies also indicate that two new types of interactions are important for understanding the stability of our fluids and for predicting their transport properties: (i) An entropic attraction force arising from attachment of the effective solvent to the core particles; and (ii) Electrostatic forces due to surface-attached, bendable dipoles on the cores.Broader Impacts: The NIMS core particle is an inorganic nanostructure. This open possibility for creating entirely new types of hybrid fluids based upon the vast library of available inorganic particle chemistries and shapes. The unique properties possible in such fluids makes them attractive for a host of applications, including high-conductivity heat-transfer liquids, inkjet printable semiconducting inks, stable electrolytes for high-temperature batteries, light-weight conformal armor for military and law-enforcement personnel, and high refractive index liquids for photolithograph. Most of these applications are inaccessible to fluids created from molecular building blocks. The proposed research is the first attempt to develop fundamental understanding of the interaction forces that control structure and properties of these types of fluids. We believe that our work will provide crucial guidance on how to select components (e.g. core particle size, shape, volume fraction, corona and counterion molecular weight, and chemistry), for the many applications targeted. Furthermore, because our fluids combine elements of colloids, polymers, and complex-fluid behavior in a single material, we believe that results from the proposed research will help expand and modernize the literature on colloidal phenomena and complex fluid flows. We believe a direct result of the range of applications that will be impacted by our materials, is that transfer of knowledge developed in the study to the classroom will be more rapid than normal for subjects in the field. The novelty of NIMS and their relevance to easily appreciated applications also provides new opportunities for attracting younger students (K-12) to science. Specifically, in collaboration with the Cornell Center for Materials Research (CCMR), we will develop demonstrations based on applications of the materials, e.g. as inkjet printable inks, conformal body armor, and high-index liquids for photolithography. Our goals for these demonstrations are to engage students at an early age to think about materials in terms of their fundamental units or building blocks, and to recognize the connection between physical properties and the forces between these units. We also believe that video demonstrations connecting flow transitions in NIMS to structural transitions revealed by scattering experiments will help advanced students appreciate relationships between transport properties of complex fluids and their interactions. We will use these video demonstrations in our undergraduate Fluid Mechanics (ChemE 323) and graduate Polymer Physics (ChemE 745) courses, and also plan to take advantage of the YouTube web portal to disseminate them to a broader audience.