Thermodynamic and Dynamic Control of Nanoparticles in Polymer Matrices

聚合物纳米复合材料是柔性长链分子（聚合物）和硬功能颗粒的混合物，从汽车轮胎到油漆和粘合剂的日常应用中都可以找到。为了促进科学的进步，这个项目的重点是研究聚合物纳米复合涂层，这种涂层有可能提高太阳能电池设备的能力，利用更广泛的太阳光谱，从而更有效地生产能源。该项目试图解决的根本问题是如何通过控制颗粒的分布来改变不同材料的性质。除了实验之外，计算机模拟将用于指导聚合物和颗粒的选择，并帮助解释实验结果。嵌段共聚物是由两种不同的聚合物分子相互连接而成的，它将被操纵成水平和垂直交替的结构域（就像一叠卡片），其中包含具有互补功能的纳米颗粒。为了确定颗粒的位置和聚集体的大小，将使用最先进的表征工具。这项研究将产生相图，以确定促进聚合物和颗粒之间良好混合的环境条件。除了培养出受过良好教育、有科学技能的劳动力外，科研和教育的结合还在几个层面上造福社会。例如，研究生和本科生将参加一年一度的公共活动，包括宾夕法尼亚大学的纳米技术日、费城材料日和费城科学节。另一个令人兴奋的拓展项目是工程数学和科学女孩营（GEMS），这是一个为期一周的日间营地，向特拉华山谷的中学女孩介绍科学、技术、工程和数学。该项目的目标是了解控制嵌段共聚物（bcp）中纳米颗粒（NPs）空间分布和组装的基本原理，并了解聚合物纳米复合材料（pnc）的热力学和相分离途径。总体目标是进行系统的研究，建立在聚合物和NP扩散的专业知识，以及NP组装在pnc。(1)第一个目标是调整等离子体纳米粒子与水平和垂直排列的片层状纳米粒子之间的纳米级分离。通过聚合物刷功能化NP，两种NP将位于交替的BCP结构域。研究了畴间距和颗粒载荷的影响。PNC场理论模拟（PNC- ft）将用于确定这些PNC的自由能和预测柱状到层状的相变。(2)第二个目标是研究二元（A/NP）和三元（A/B/NP） pnc的热力学行为。相图将使用透射电子显微镜（TEM）对等温样品以及新的原位x射线散射能力进行绘制。与第一个目标一样，PNC-FT将为选择材料参数提供指导，并帮助解释结果。(3)第三个目标是研究二元（A/NP） pnc的相分离动力学，以阐明决定动力学捕获体系中聚集体大小和渗透形态的基本参数。PNC-FT修改，包括动力学将指导实验，并提供洞察热力学和动力学之间的平衡，决定最终形态。粒子扩散将用卢瑟福后向散射光谱法测量。聚合物刷弛豫和离子扩散通过渗透形态也将被测量。综上所述，虽然这是基础性的，但所提出的工作有可能创造出具有增强上转换发光和快速离子迁移率的pnc，这对太阳能和储能装置分别具有重要意义。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYPolymer nanocomposites, mixtures of flexible long-chain molecules (polymers) and hard functional particles, are found in everyday applications from automobile tires to paints and adhesives. To promote the progress of science, the focus of this project is to study polymer nanocomposite coatings that have the potential to improve the ability of solar cell devices to utilize a broader section of the solar spectrum allowing for more efficient energy production. The fundamental issue that the project seeks to address is how to combine dissimilar materials in such a way that the properties can be varied by controlling how well the particles are distributed In addition to experiments, computer simulations will be used to guide the selection of polymer and particles and to help interpret experimental results. Block copolymers, which are two different polymer molecules tied to each other, will be manipulated to create horizontal and vertical alternating domains (like a stack of cards) that contain nanoparticles of complementary functionality. To determine the location of particles and size of aggregates, state-of-the-art characterization tools will be used. This research will produce phase diagrams that allow for the determination of environmental conditions that promote good mixing between the polymer and particles. Besides producing a well-educated, scientifically skilled workforce, the integration of research and education benefits society at several levels. For example, graduate and undergraduate students will participate in annual public events including Nanotechnology Day at Penn, Philly Materials Day, and the Philadelphia Science Festival. An additional exciting outreach program is Girls in Engineering Mathematics and Science Camp (GEMS), a weeklong day-camp that introduces middle-school girls from the Delaware Valley to Science, Technology, Engineering, and Math. TECHNICAL SUMMARYThe goal of this project is to understand the fundamental principles that control the spatial distribution and assembly of nanoparticles (NPs) in block copolymers (BCPs) and to understand the thermodynamics and phase separation pathways of polymer nanocomposites (PNCs). The overarching goal is to perform systematic studies that build on expertise in polymer and NP diffusion as well as NP assembly in PNCs. (1) The first aim is to tune the nanoscale separation between plasmonic NPs and upconverting nanoplates/nanospheres in horizontally and vertically aligned lamellar BCPs. By functionalizing the NP with polymer brushes, the two NP species will be located in alternating BCP domains. The effect of domain spacing and particle loading will be investigated. PNC field-theoretic simulations (PNC-FT) will be used to determine the free energies of these PNCs and predict the cylinder-to-lamellar phase transition. (2) The second aim is to study the thermodynamic behavior of binary (A/NP) and ternary (A/B/NP) PNCs. The phase diagrams will be mapped out using transmission electron microscopy (TEM) on isothermal samples as well as the new in situ X-ray scattering capabilities. As in the first aim, PNC-FT will provide guidance for selecting materials parameters and help interpret results. (3) The third aim is to investigate phase separation dynamics of binary (A/NP) PNCs to elucidate the fundamental parameters that determine aggregate size and percolating morphologies in kinetically trapped systems. PNC-FT modified to include dynamics will guide experiments and provide insight into the balance between thermodynamics and dynamics that dictate the final morphology. Particle diffusion will be measured using Rutherford backscattering spectrometry. Polymer brush relaxation and ion diffusion through percolated morphologies will also be measured. In summary, although fundamental in nature, the proposed work has the potential to create PNCs with enhanced upconversion luminescence and fast ion mobility, which is of importance for solar energy and energy storage devices, respectively. .This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.