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，在从汽车轮胎到油漆和粘合剂的日常应用中发现。 为了促进科学的进步，该项目的重点是研究聚合物纳米复合材料涂层，这些涂层有可能提高太阳能电池设备利用更广泛的太阳光谱的能力，从而实现更有效的能源生产。该项目寻求解决的根本问题是如何将不同的材料组合在一起，以便通过控制颗粒的分布来改变性能。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，这是两个不同的聚合物分子彼此相连，将被操纵，以创建水平和垂直交替域（如一叠卡片），其中包含互补功能的纳米粒子。为了确定颗粒的位置和聚集体的尺寸，将使用最先进的表征工具。 这项研究将产生相图，允许确定促进聚合物和颗粒之间良好混合的环境条件。 除了培养受过良好教育、具有科学技能的劳动力外，研究和教育的结合还在多个层面上造福社会。例如，研究生和本科生将参加年度公共活动，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。 另一个令人兴奋的外展计划是女孩在工程数学和科学营（GEMS），为期一周的一天营，介绍中学女孩从特拉华州山谷科学，技术，工程，本项目的目标是了解控制嵌段共聚物（BCP）中纳米颗粒（NP）的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扩散以及NP组装在PNC的专业知识。(1)第一个目的是调节水平和垂直对齐的层状BCP中等离子体纳米粒子和上转换纳米片/纳米球之间的纳米级分离。通过用聚合物刷官能化NP，两种NP物质将位于交替的BCP域中。将研究畴间距和颗粒负载的影响。PNC场理论模拟（PNC-FT）将被用来确定这些PNC的自由能和预测的圆柱状层状相变。(2)第二个目标是研究二元（A/NP）和三元（A/B/NP）PNCs的热力学行为。相图将绘制出使用透射电子显微镜（TEM）的等温样品，以及新的原位X射线散射能力。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)第三个目的是调查相分离动力学的二元（A/NP）PNCs，以阐明的基本参数，确定聚集体的大小和在动力学捕获系统的结晶形态。修改后的PNC-FT包括动力学将指导实验，并提供对决定最终形态的热力学和动力学之间的平衡的洞察。将使用卢瑟福背散射光谱法测量颗粒扩散。 还将测量聚合物刷松弛和离子扩散通过结晶形态。总之，虽然本质上是基础性的，但所提出的工作具有创建具有增强的上转换发光和快速离子迁移率的PNC的潜力，这分别对于太阳能和能量存储器件是重要的。 该奖项反映了NSF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.