Polymer Nanocomposites using Discrete Nanoparticles and Bicontinuous Scaffolds: New Strategies for Connective Morphologies and Property Control

聚合物纳米复合材料是柔性长链分子（聚合物）和硬功能颗粒的混合物。 虽然在从轮胎到油漆的日常材料中发现，但聚合物纳米复合材料在从储能到水净化的应用中也具有作为先进功能材料的未来潜力。 这项研究将提供对化学，物理和工程原理的基本理解，这些原理可以结合在一起来研究一种新型的复合材料，该复合材料包含带电聚合物和涂覆有类似或不同带电聚合物的颗粒的混合物，以实现传统复合材料不可能实现的特性。 简而言之，总的目标是促进科学的进步，导致新的和改进的先进材料。 一个基本问题是控制分子间的相互作用，这种相互作用决定了颗粒在复合材料中的分布方式。这种“混合”方法的一个挑战是颗粒聚集的趋势。 为了克服这一限制，本研究的第二个基本问题是制造高负载复合材料，其中聚合物被纳入支架中，类似于水溶胀海绵。 为了加速新材料的发现，将使用智能实验方法，对数据进行表征并立即反馈，以制定新的复合材料。 这一过程将持续到找到最佳配方。进行这项研究的学生将获得数据科学方面的宝贵技能，增加就业机会，并学会可持续地利用宝贵的资源（材料，设备）。研究生和本科生还参加年度公共活动，包括宾夕法尼亚大学的纳米技术日，费城材料日和费城科学节。 一个特别独特的计划是“第一次接触STEM研究”，它提供了一个结构，介绍第一代，低收入学生到他们的第一个研究项目。聚合物纳米复合材料（PNC）的结构决定了其性能。然而，PNC的全部潜力受到缺乏对结构-性质关系的控制的阻碍，部分原因是非平衡结构的普遍存在。在这里，PNCs含有离散的纳米粒子（NP）在聚合物基质或那些从双连续，纳米多孔支架制造的设计，加工和表征，以了解其基本的热力学，界面和动力学原理。 本工作的目的是（1）阐明刷电荷密度如何影响NP分散在不同电荷和极性的聚乙烯（PE）基质中，并探索走向分散结构的动力学途径，（2）研究极性聚合物渗透到支架中的动力学，（3）发展自主实验（AE），以加速发现具有不同结构的PNC。目的1研究极性增加的聚合物基质中的PE-NPs。目的1a研究PE-NP/基质相容性，以深入了解刷-基质静电相互作用。目的1b研究相分离，以指导识别产生带电刷逾渗的动力学途径。目的2a和2b分别研究用极性基质聚合物渗透的双连续金属和聚合物支架。渗透动力学和性能的孔隙限制和支架类型的功能进行了研究。这些研究的意义在于发现了用于增强能量储存或水净化应用的制造（双）连续结构的途径。在目标3中，AE光学显微镜将用于绘制PNC的相图，而AE-GISAXS与布鲁克海文国家实验室的科学家合作，将确定产生具有有利机械性能和导电性的PNC结构的材料和加工条件。 总之，PNC的基础研究与数据科学驱动的表征相结合，将协同作用，以促进该项目中材料发现的知识。该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

NON-TECHNICAL SUMMARY:Polymer nanocomposites are mixtures of flexible long-chain molecules (polymers) and hard functional particles. Although found in everyday materials from tires to paints, polymer nanocomposites also have future potential as advanced functional materials in applications from energy storage to water purification. This research will provide a fundamental understanding of chemistry, physics and engineering principles that can be brought together to investigate a new type of composite containing a mixture of charged polymers and particles coated with similar or different charged polymers to achieve properties not possible with traditional composites. In short, the overall goal is to promote the progress of science leading to new and improved advanced materials. One fundamental issue is controlling molecular interactions that determine how particles are distributed in a composite material. One challenge with this “mixing” approach is a tendency for particles to aggregate. To overcome this limitation, a second fundamental issue in this study is the fabrication of highly loaded composites where the polymer is incorporated into a scaffold, analogous to water swelling a sponge. To accelerate the discovery of new materials, a smart experimental approach will be used where data will be characterized and fed back immediately to formulate a new composite. This process is continued until the optimum formulation is found. Students performing this research will gain valuable skills in data science, enhancing career opportunities, and learn to utilize valuable resources (materials, equipment) sustainably. Graduate and undergraduate students also participate in annual public events including Nanotechnology Day at Penn, Philly Materials Day, and the Philadelphia Science Festival. A particularly unique program is “First Exposure to Research in STEM,” which provides a structure for introducing first-generation, low-income students to their first research project. TECHNICAL SUMMARY:Polymer nanocomposite (PNC) structure determines their properties. However, the full potential of PNCs is hindered by lack of control over structure-property relationships, partly due to the prevalence of non-equilibrium structures. Here, PNCs containing discrete nanoparticles (NP) in a polymer matrix or those fabricated from bicontinuous, nanoporous scaffolds are designed, processed and characterized to understand their fundamental thermodynamic, interfacial, and dynamic principles. The objectives of this work are to (1) elucidate how brush charge density affects NP dispersion in polyelectrolyte (PE) matrices of varying charge and polarity and explore kinetic pathways towards percolated structures, (2) investigate infiltration kinetics of polar polymers into scaffolds, and (3) develop autonomous experimentation (AE) to accelerate discovery of PNCs with distinct structures. Aim 1 investigates PE-NPs in polymer matrices of increasing polarity. Aim 1a studies PE-NP/matrix miscibility to provide insight into brush-matrix electrostatic interactions. Aim 1b studies phase separation to guide the identification of kinetic pathways that produce percolation of charged brushes. Aims 2a and 2b investigate bicontinuous metal and polymer scaffolds, respectively, infiltrated with polar matrix polymers. Infiltration kinetics and properties are studied as a function of pore confinement and scaffold type. The significance of these studies involves the discovery of pathways for fabricating (bi)continuous structures for enhanced energy storage or water purification applications. In Aim 3, AE-optical microscopy will be used to map the phase diagram of PNCs, whereas AE-GISAXS, in collaboration with scientists from Brookhaven National Laboratory, will identify materials and processing conditions that produce percolated PNC structures with advantageous mechanical properties and conductivity. In summary, fundamental studies of PNCs) combined with data-science-driven characterization will act synergistically to advance knowledge for materials discovery in this project..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.