Directed Assembly of Nanoparticles into Composite Materials

美国国家科学基金会-化学运输系统分部颗粒多相过程计划（1415）提案编号：0652073主要研究者：Wong，MichaelAffiliation： William Marsh Rice大学提案标题：纳米颗粒定向组装成复合材料知识分子优点胶囊材料用于医药、食品、化妆品和涂料等不同的应用领域。在开发新的胶囊合成路线方面已经取得了重大进展，但仍然存在关于宽粒度分布、不可缩放性和低结构稳定性的问题。一种新报道的方法涉及将带负电荷的纳米颗粒悬浮液与带正电荷的聚合物和多价阴离子的溶液混合，导致纳米颗粒明显自组织成微米尺寸的胶囊结构。然而，这种独特的材料合成路线背后的基本化学原理还没有得到很好的理解。该提案描述了一个为期三年的研究和教学计划，重点是理解解释这种特殊形式的纳米颗粒组装的相关物理化学和胶体科学概念。解决这个问题“什么是控制微胶囊的纳米粒子组装合成的原则”，新知识将有助于推进材料化学，特别是通过（i）改善微胶囊性能的控制，（ii）提高将纳米粒子悬浮液加工成功能先进材料的能力，以及（iii）作为新兴合成工具的定向纳米粒子组装领域。本计画的具体研究目标是加深对聚合物聚集体作为带电胶体物种的理解，并确定壳壁的形成机制。成功完成所提出的任务（1）将根据酸碱化学和DLVO理论解释pH对聚合物聚集体形成的影响，（2）将根据带电纳米颗粒/聚合物聚集体相互作用解释pH对微胶囊形成的影响，（3）将为聚合物聚集体生长的聚结机制提供证据，和（4）将支持壳形成的扩散-沉积模型，其中纳米颗粒尺寸控制微胶囊壳厚度。更广泛的影响纳米颗粒构建块的使用是材料研究的重要领域，这个项目的结果应该会激发一种新的方法来研究基于纳米颗粒的结构。这种形式的纳米颗粒组装是相当普遍的，这表明具有新的组成和功能的空心球结构以及全新的基于纳米颗粒的架构是可能的。温和的合成条件和微胶囊的结构特性提供了可扩展性，易于封装和潜在应用的优点。最终，对NP组装化学的更深入理解将有助于改善对技术相关材料的结构控制，并更好地理解带电聚合物/多价阴离子和带电NP/带电聚合物的相互作用。通过本研究项目，学生研究人员将学习和发展以工程概念应用为指导的前沿科学。他们将进行跨学科研究;使用和开发最先进的合成和表征技术;并指导本科研究人员。该项目将为女生和代表性不足群体的学生提供支助。提出了三个新的教育/推广活动：基于NP组装的实验室模块，休斯顿地区的高中教师托管计划，以及高中教师科学课程开发计划，后两个与美国国家科学基金会NSEC中心在赖斯大学的协调。

National Science Foundation - Division of Chemical &Transport Systems Particulate & Multiphase Processes Program (1415)Proposal Number: 0652073Principal Investigators: Wong, MichaelAffiliation: William Marsh Rice UniversityProposal Title: Directed Assembly of Nanoparticles into Composite MaterialsIntellectual MeritCapsule materials are used in application areas as diverse as medicine, foods, cosmetics, and paints. There have been significant advances in the development of new capsule synthesis routes, but there remain issues concerning wide particle size distribution, non-scalability, and low structural stability. A newly reported method involves mixing a negatively charged nanoparticle suspension with solutions of a positively-charged polymer and a multivalent anion, leading to the apparent self-organization of nanoparticles into micron-sized capsule structures. The underlying chemistry behind this unique materials synthesis route is not well understood, however. This proposal describes a three-year research and teaching plan that focuses on understanding the relevant physical chemistry and colloid science concepts that explain this particular form of nanoparticle assembly. Addressing the question "What are the principles that govern the nanoparticle assembly synthesis of microcapsules," the new knowledge will serve to advance materials chemistry, specifically by (i) improving the control of microcapsule properties, (ii) increasing one's ability to process nanoparticle suspensions into functional advanced materials, and (iii) contributing to the field of directed nanoparticle assembly as an emerging synthesis tool. The specific research objectives of this project are to gain a stronger understanding of polymer aggregates as charged colloid species; and to ascertain the formation mechanism of the shell walls. The successful completion of the proposed tasks (1) will explain the pH effect on polymer aggregate formation in terms of acid-base chemistry and DLVO theory, (2) will explain the pH effect on microcapsule formation in terms of charged nanoparticle/polymer aggregate interactions, (3) will provide evidence for a coalescence mechanism for polymer aggregate growth, and (4) will support a diffusion-deposition model for shell formation in which nanoparticle size controls the microcapsule shell thickness.Broader ImpactsThe use of nanoparticle building blocks is an important area of materials research, and the results from this project should inspire a fresh approach to nanoparticle-based structures. This form of nanoparticle assembly is quite general, suggesting hollow sphere structures with new compositions and functionalities and entirely new nanoparticle-based architectures are possible. The mild synthesis conditions and the structural properties of microcapsules provide advantages of scalability, ease of encapsulation, and potential applications. Ultimately, a stronger understanding of the NP assembly chemistry will contribute to improved structural control over a technologically relevant material, and to a better understanding of charged-polymer/multivalentanion and charged-NP/charged-polymer interactions.Through this research project, student researchers will learn and develop cutting-edge science guided by the application of engineering concepts. They will perform interdisciplinary research; use and develop state-of-the-art synthesis and characterization techniques; and mentor undergraduate researchers. Female students and students from underrepresented groups will be supported in this project. Three new educational/outreach activities are proposed: a lab module based on NP assembly, a Houston-area high school teacher hosting program, and a high school teachers science lessons development program, with the latter two in coordination with the NSF NSEC center at Rice University.