Directed Assembly of Nanoparticles into Composite Materials

美国国家科学基金会-化学与运输系统颗粒与多阶段处理计划(1415)提案编号：0652073主要研究人员：Wong，Michael从属：William Marsh Rice大学提案标题：纳米颗粒定向组装成复合材料智能胶囊材料应用领域广泛，如医药、食品、化妆品和涂料。在新的胶囊合成路线的开发方面已经取得了重大进展，但仍然存在粒度分布宽、不可伸缩性和结构稳定性低的问题。一种新报道的方法包括将带负电的纳米颗粒悬浮液与带正电的聚合物和多价阴离子的溶液混合，导致纳米颗粒明显地自组织成微米级的胶囊结构。然而，这种独特的材料合成路线背后的潜在化学成分还没有被很好地理解。这项提案描述了一项为期三年的研究和教学计划，重点是了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。这一新知识将有助于推动材料化学的发展，特别是通过(I)改进对微胶囊性能的控制，(Ii)提高将纳米颗粒悬浮液加工成功能先进材料的能力，以及(Iii)将定向纳米颗粒组装作为一种新兴的合成工具。本项目的具体研究目标是更深入地了解聚合物聚集体作为带电胶体物种的情况，并确定壳壁的形成机理。这些任务的成功完成(1)将从酸碱化学和DLVO理论方面解释pH对聚合物聚集体形成的影响，(2)将从带电纳米粒子/聚合物聚集体相互作用的角度解释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，以及(4)将支持纳米粒子尺寸控制微胶囊壳层厚度的壳层形成扩散-沉积模型。这种形式的纳米颗粒组装是非常普遍的，这意味着具有新的组成和功能的空心球结构和全新的基于纳米颗粒的结构是可能的。微胶囊具有温和的合成条件和良好的结构特性，具有可伸缩性、易包封性和潜在的应用前景。最终，对NP组装化学的更好的理解将有助于改善对技术相关材料的结构控制，并有助于更好地了解带电聚合物/多价阴离子和带电聚合物/带电聚合物的相互作用。通过这个研究项目，学生研究人员将学习和发展应用工程概念指导的尖端科学。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；并指导本科生研究人员。该项目将支持女学生和代表人数不足群体的学生。提议开展三项新的教育/外联活动：基于NP组装的实验室模块、休斯顿地区高中教师托管方案和高中教师科学课程发展方案，后两项活动与莱斯大学NSF NSEC中心协调。

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.