Controlling Nanocomposite Properties by Nanoparticle Assembly

非技术概要：聚合物纳米复合材料是聚合物材料和纳米尺寸的无机颗粒的混合物，一直受到人们的关注，主要是因为相对于相应的纯聚合物，它们提供了显著改善物理性能的希望。虽然迄今为止已经有很多关于这些主题的研究，但很少有人从控制纳米颗粒（NP）分散的相关科学细节到优化实际相关的热性能和机械性能。本研究项目的三个方面都侧重于以一种对应用程序有直接影响的方式建立这种联系。(i)关于压力效应的拟议研究将描述加工在均质化聚合物/NP混合物中的作用，以及这种变化的分散状态对性能的影响。（ii）在第二条线索中，本研究将研究NP形状在优化热性能和机械性能方面的作用。（iii）最后，将通过用物理连接的聚合物分子取代NPs上的化学连接的聚合物分子来探索拟议研究的实际后果。这些策略是否相同，如果不是，它们在哪些切实的方面不同？这些研究工作将与一系列教育和外联活动相结合。受该组织最近为暑期研究招募高中生和本科生的活动的推动，该提案将继续招募历史上少数民族学校（如佛罗里达农工大学）的学生，以及来自大纽约市环境的本科生和高中生（和教师）。PI的小组此前曾与几名女性和少数族裔高中学生合作，这些学生随后在大学里学习科学和工程，并将继续这种通往科学和工程职业的管道方法。技术概述：人们对聚合物纳米复合材料一直很感兴趣，主要是因为这些杂化材料相对于纯聚合物具有显著的性能改进。虽然迄今为止关于这一主题的研究很多，但很少有人从控制纳米颗粒（NP）的分散状态到优化所出现的热机械性能。提出的整体方法，结合实验和理论，通过(a)研究组装过程的基本原理及其对性能的影响，以及(b)将不断发展的理解移植到更适合应用的地方，精确地集中在弥合这一差距上。建议的研究有以下三个方面：(i)批判性地研究压力在聚合物/NP混合物均质化中的作用。高压可以用来控制NP分散吗？高压对性能有什么影响？（ii）同样，该研究将探索NP形状作为进一步优化热机械性能的途径的作用。（iii）最后，将通过用链的物理吸附取代NPs上的化学接枝链来研究拟议研究的实际后果。这个想法可行吗？就物业改善而言，它的优点和缺点是什么？这些研究活动与广泛的教育和外联活动相结合。由于该组织最近的活动涉及高中生和本科生的暑期研究，以及该组织与佛罗里达农工大学（一个HBCU）的良好互动，该提议将继续在高中、本科生和研究生阶段招募代表性不足的学生（包括女性和少数族裔），作为该组织研究工作的一部分。PI还与纽约城市学院化学工程系合作，将大纽约地区的学者（教师和学生）、地方工业和国家实验室聚集在一起，举行一年一度的化学工程研讨会。其目标不仅是让毕业的学生进入当地的工业，而且还吸引工业参与者进入哥伦比亚大学的更高学位和/或进修课程。

NON-TECHNICAL SUMMARY:There has been continuing interest in polymer nanocomposites, which are mixtures of polymeric materials and nanometer-sized inorganic particles, primarily because they offer the promise of significantly improved physical properties relative to the corresponding pure polymer. While there have been many studies on these topics to date, very few have gone from the scientific details relevant to controlling the nanoparticle (NP) dispersions to optimizing the practically relevant thermal and mechanical properties that emerge. Each of the three prongs of this research project focuses on establishing this connection in a way that has a direct impact on applications. (i) The proposed research on pressure effects will delineate the role of processing in homogenizing polymer/NP mixtures and the consequences of this changing dispersion state on properties. (ii) In a second thread, this research will study the role of NP shape on optimizing thermal and mechanical properties. (iii) Finally, the practical consequences of the proposed research will be explored by replacing chemically attached polymer molecules on the NPs by the physically attached ones. Are these strategies equivalent, and, if not, in what tangible ways are they different?These research efforts will be coupled to a suite of education and outreach activities. Driven by the group's recent activities involving recruiting high school and undergraduate students for summer research, the proposal is to continue to recruit students from historically minority schools (such as Florida A&M), as well as undergraduate and high school students (and teachers) from the greater New York City environment. The PI's group has previously worked with several women and minority high-school students who have subsequently gone on to study science and engineering in college, and will continue this pipeline approach toward science and engineering careers.TECHNICAL SUMMARY:There has been continuing interest in polymer nanocomposites, primarily because these hybrids offer the promise of significant property improvements relative to the pure polymer. While there have been many studies on this topic to date, very few of them have gone all the way from controlling the nanoparticle (NP) dispersion state to optimizing the thermomechanical properties that emerge. The overall approach proposed, which combines experiments and theory, focuses precisely on bridging this gap by (a) studying the fundamentals of the assembly process and its consequences on properties, and (b) porting the evolving understanding to make it more amenable to applications. The proposed research has the following three prongs: (i) Critically studying the role of pressure in homogenizing polymer/NP mixtures. Can high pressure be used to control NP dispersion and what are its effects on properties? (ii) Similarly, the research will explore the role of NP shape as a route to further optimizing thermomechanical properties. (iii) Finally, the practical consequences of the proposed research will be studied by replacing chemically-grafted chains on the NPs by the physical adsorption of chains. Is this idea feasible and what are its advantages and disadvantages in terms of property improvements?These research activities are coupled to extensive education and outreach activities. Driven by the group's recent activities involving high school and undergraduate students for summer research, and with the group's well-developed interactions with Florida A&M University (an HBCU), the proposal is to continue to recruit underrepresented students (both women and minorities) at the high school, undergraduate and graduate levels to be part of the group's research efforts. The PI is also working with the Chemical Engineering department at the City College of New York to bring together academics in the Greater New York area (faculty and students), local industry and national laboratories in an annual chemical engineering symposium. The goal is, not only to place graduating students into local industry, but also to attract industrial participants into higher degree and/or refresher programs at Columbia.