Vertically Oriented Anisotropic Nanoparticles in Polymer Matrices

非技术综述：为了促进聚合物科学的进步，本项目的重点是聚合物纳米复合材料。由于聚合物-纳米复合材料是众多应用的基础，它们的研究影响和改进了各种技术，从复杂的设备，如生产太阳能电池的复杂设备，到日常材料，如更轻的包装。该项目寻求解决的基本问题是那些管理嵌段共聚物中各向异性粒子组装的问题。具体地说，该项目将生产垂直取向的各向异性粒子，并控制规则的分离，这样做将促进对具有特殊几何结构的聚合物材料中纳米棒和纳米板的理解，例如基质中的纳米柱或交替的纳米片。由此产生的关于如何自组装垂直定向纳米颗粒的见解将使科学界能够探索各种各向异性性质，包括分子、电学和热传输。这项研究的成功成果将是精确控制聚合物纳米复合膜中纳米棒和纳米板的垂直取向和横向间距，这将在纳滤、传感、屏障涂层和照明等领域对社会产生潜在的好处。除了培养一支受过良好教育、具有科学技能的劳动力队伍外，研究和教育的融合还在几个层面上造福于社会。除了研究生教育，来自美国和海外的本科生以及费城当地的高中参与者将从研究和指导中受益。为了吸引更广泛的受众，研究人员将每年参加Nanoday@Penn和费城材料日，分别吸引200多名高中生和2000名参与者。此外，一年一度的教师材料科学研讨会将继续以及与费城中央高中的独特合作伙伴关系，这将使大量少数族裔学生群体接触到STEM领域的机会。技术摘要：将研究控制嵌段共聚(BCP)薄膜中纳米棒和纳米板垂直排列的热力学和动力学原理。各向异性粒子将被嫁接上聚合物刷子，以控制它们与其他粒子和BCP的相互作用。研究目标是：(1)在嵌段共聚物的垂直圆柱形区域内垂直排列纳米棒。金属、纳米荧光粉和半导体纳米棒将在聚(苯乙烯-b-2-乙烯基吡啶)(PS-b-P2VP)和P2VP薄膜中进行研究。纳米棒的直径和长度对垂直取向的影响是特别令人感兴趣的，以及使用纳米棒的二元混合物将它们引导到特定的微域。(2)在嵌段共聚物的垂直片层结构域中垂直排列纳米板。氧化石墨烯、纳米荧光粉和磷灰石纳米板将在聚(苯乙烯-b-甲基丙烯酸甲酯)(PS-b-PMMA)和PS薄膜中进行研究。(3)研究了均聚物和嵌段共聚物薄膜在溶剂退火过程中纳米棒的组装动力学。单粒子跟踪将用于测量纳米棒的迁移率。修改后的包含动力学的场论模拟将指导实验，并提供对热力学和动力学之间的平衡的洞察，从而区分最终的形态。研究利用新的和持续的合作来创建新的粒子-聚合物组件，执行原位表征，并对垂直排列的聚合物纳米复合材料进行建模。具体地说，分散性将作为颗粒形状、尺寸和表面化学、膜厚度和界面相互作用以及BCP组成和尺寸的函数进行研究。三维场理论模拟将指导实验参数的选择，并为理解粒子和BCP取向之间的相互作用提供热力学框架。用透射电子显微镜、原子力显微镜和小角X射线衍射仪测定BCP的形貌，用透射电子显微镜、原子力显微镜和扫描电子显微镜确定颗粒的位置，用RBS进行深度剖析。GISAXS将被用来跟踪在溶剂热处理过程中的原位结构演变。光学性质将通过UV-Vis光谱来表征。这项研究得益于与桑迪亚国家实验室和先进光源公司的无资金支持的合作。

NON-TECHNICAL SUMMARY:To promote the progress of polymer science, this project is focused on polymer nanocomposites. Because they underlie so many applications, polymer-nanocomposite research impacts and improves technologies ranging from complex devices, such as energy producing solar cells, to everyday materials, such as lighter packaging. The fundamental issues that the project seeks to address are those that govern the assembly of anisotropic particles in block copolymers. Specifically, the project will produce vertically-oriented, anisotropic particles with controlled regular separations, and in so doing will advance understanding of nanorods and nanoplates in polymeric materials having special geometries such as nanocylinders in a matrix or alternating nanosheets. The resulting insights about how to self-assemble vertically oriented nanoparticles will enable the scientific community to explore a variety of anisotropic properties including molecular, electrical, and thermal transport. A successful outcome of the proposed research will be precise control over the vertical orientation and lateral spacing of nanorods and nanoplates in polymer nanocomposite films, which have potential benefits to society in areas of nanofiltration, sensing, barrier coatings and lighting. Besides producing a well educated, scientifically skilled work force, the integration of research and education benefits society at several levels. Besides graduate education, undergraduates from the US and abroad as well as local Philadelphia high school participants will benefit from research and mentoring. To reach a broad audience, researchers will participate annually in Nanoday@Penn and Philly Materials Day, which attract over 200 high school students and 2000 attendees, respectively. Furthermore, the annual Teachers Materials Science Workshop will continue as well as a unique partnership with Central High School, Philadelphia, which exposes a large minority student population to opportunities in STEM fields.TECHNICAL SUMMARY:The thermodynamic and dynamic principles that control vertical alignment of nanorods and nanoplates in block copolymer (BCP) films will be investigated. Anisotropic particles will be grafted with polymer brushes to control their interactions with other particles and BCP. Research objectives are to: (1) Vertically align nanorods in perpendicular cylindrical domains of block copolymers. Metallic, nanophosphor and semiconducting nanorods will be investigated in poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) and P2VP films. The effect of nanorod diameter and length on vertical orientation is of particular interest, as well as using binary mixtures of nanorods to direct them to specific microdomains. (2) Vertically align nanoplates in perpendicular lamella domains of block copolymers. Graphene oxide, nanophosphor and laponite nanoplates will be investigated in poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and PS films. (3) Investigate the dynamics of nanorod assembly in homopolymer and block copolymer films during solvent annealing. Single particle tracking will be used to measure nanorod mobility. Field theoretic simulations modified to include dynamics will guide experiments and provide insight into the balance between thermodynamics and dynamics that differentiates the final morphology.The research leverages new and continuing collaborations to create novel particle-polymer assemblies, perform in situ characterization, and model vertically aligned polymer nanocomposites. Specifically, dispersion will be studied as a function of particle shape, size and surface chemistry, film thickness and interface interactions, and BCP composition and size. Three-dimensional field theoretic simulations will guide the choice of experimental parameters and provide a thermodynamic framework for understanding the interplay between particle and BCP orientation. BCP morphology will be determined by TEM, AFM and SAXS, particle location by TEM, FIB-SEM and depth profiling by RBS. GISAXS will be used to follow in situ structural evolution during solvent annealing. Optical properties will be characterized by UV-vis spectroscopy. This research benefits from unfunded collaborations with Sandia National Laboratories and the Advanced Light Source.