Controlling Nanocomposite Properties by Nanoparticle Assembly

非技术综述：聚合物纳米复合材料是聚合物材料和纳米无机颗粒的混合物，一直受到人们的关注，主要是因为它们提供了相对于相应的纯聚合物显著改善物理性能的前景。虽然到目前为止已经有很多关于这些主题的研究，但从控制纳米颗粒(NP)分散的科学细节到优化出现的实际相关的热和机械性能的研究很少。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阐明加工在使聚合物/NP混合物均质化方面的作用，以及这种分散状态的变化对性能的影响。(Ii)在第二条线索中，本研究将研究NP形状对优化热性能和力学性能的作用。(Iii)最后，将探讨拟议研究的实际后果，即用物理附着的聚合物分子取代NPs上的化学附着的聚合物分子。这些战略是否等同？如果不是，它们在哪些具体方面存在差异？这些研究工作将与一系列教育和外联活动相结合。在该组织最近招募高中生和本科生参加暑期研究活动的推动下，该计划将继续从历史上少数族裔学校(如佛罗里达农工大学)招收学生，以及从大纽约市环境中招收本科生和高中生(以及教师)。PI的团队之前曾与几名女性和少数族裔高中生合作，他们后来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。技术摘要：人们对聚合物纳米复合材料一直感兴趣，主要是因为这些杂化材料有望比纯聚合物有显著的性能改进。虽然到目前为止已经有很多关于这一主题的研究，但从控制纳米粒子(NP)的分散状态到优化出现的热机械性能的研究很少。提出的整体方法结合了实验和理论，恰好侧重于通过以下方式弥合这一差距：(A)研究组装过程的基本原理及其对性能的影响，以及(B)移植不断发展的理解，使其更适合应用。拟议的研究有以下三个方面：(I)批判性地研究压力在均质聚合物/NP混合物中的作用。高压能用来控制NP的分散吗？它对性能有什么影响？(Ii)同样，这项研究将探索NP形状作为进一步优化热力性能的途径的作用。(3)最后，将研究拟议研究的实际结果，用链的物理吸附取代化学接枝到NPs上的链。这个想法可行吗？它在物业改善方面的优势和劣势是什么？这些研究活动与广泛的教育和外展活动相结合。受该组织最近针对高中生和本科生进行暑期研究的活动的推动，以及该组织与佛罗里达农工大学(HBCU)发展良好的互动，该提议是继续在高中、本科生和研究生层面招收代表性较低的学生(包括女性和少数族裔)，作为该组织研究努力的一部分。PI还与纽约城市学院的化学工程系合作，将大纽约地区的学者(教职员工和学生)、当地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。我们的目标是，不仅让应届毕业生进入当地行业，还能吸引行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.