Nanoparticle Diffusion in Complex and Dynamic Environments

CBET -1706014 PI：Winey，Karen I.许多聚合物材料用纳米颗粒改性，以提供特殊的机械，电子或光学性能。 控制纳米颗粒在整个聚合物材料中的分布对于实现这些期望的性质是必不可少的。 纳米颗粒可以通过聚合物或凝胶扩散，并且在某些情况下，在材料的加工或使用期间的扩散导致纳米颗粒的分布不均和纳米颗粒聚集，从而降低产品性能。 该奖项将支持研究纳米粒子在聚合物和凝胶中的扩散。 它将特别关注纳米颗粒尺寸与聚合物中的缠结和凝胶中的交联形成的网的尺寸相当的情况。 在这种情况下，纳米颗粒扩散取决于纳米颗粒的移动和纳米颗粒扩散通过的聚合物网中的波动。 纳米粒子的形状，纳米粒子和聚合物基体之间的相互作用，以及在聚合物基体的结构中的空间变化的影响也将被检查，并与现有的理论进行比较。 该奖项的结果将通过研究人员组织的年度研讨会传播给工业从业人员。 此外，该研究团队还将在费城材料日和宾夕法尼亚大学的年度纳米日上为公众演示纳米科学。该奖项将支持测量纳米粒子在水凝胶和缠结聚合物熔体中扩散的研究，这些研究的特征分别是它们的网孔尺寸和管径。该研究将探索纳米颗粒直径和网格尺寸或管直径相当的系统，因为模型预测在这些情况下与传统的斯托克斯-爱因斯坦扩散存在很大偏差。单粒子跟踪方法将用于测量纳米粒子在四聚（环氧乙烷）和聚丙烯酰胺水凝胶中的扩散。 四聚（环氧乙烷）水凝胶形成一个模型网络与几乎单分散的网格大小。 聚丙烯酰胺水凝胶形成具有可通过不同溶剂操纵的网孔尺寸和异质性的网络。卢瑟福背散射光谱法将被用来测量在聚苯乙烯和聚（2-乙烯基吡啶）中的苯基封端的，刷接枝的和羟基封端的纳米颗粒（球形和圆柱形）的纳米颗粒扩散系数，以探索非热的和有吸引力的纳米颗粒-聚合物相互作用。定量比较将与模型和理论在一个临界范围内的纳米粒子的比例，网孔大小，定义为爬行模型中的管直径。最后，一个纳米颗粒聚合物系统已被专门设计，以便于测量纳米颗粒扩散的单颗粒跟踪和卢瑟福背散射方法比较互补的信息，由单个纳米颗粒的运动和合奏平均从一个单一的系统。

CBET - 1706014PI: Winey, Karen I.Many polymeric materials are modified with nanoparticles to provide special mechanical, electronic, or optical properties. Controlling the distribution of the nanoparticles throughout the polymeric material is essential for achieving these desired properties. Nanoparticles can diffuse through polymers or gels, and in some cases diffusion during processing or during use of the material leads to a maldistribution of nanoparticles and nanoparticle aggregation that degrade product performance. This award will support research into the diffusion of nanoparticles in polymers and gels. It will focus specifically on the regime where the nanoparticle sizes are comparable to the size of mesh formed by entanglements in polymers and by crosslinks in gels. In this regime, nanoparticle diffusion depends on the both the movement of the nanoparticles and fluctuations in the polymer mesh through which the nanoparticles diffuse. Effects of the nanoparticle shape, interactions between the nanoparticles and the polymeric matrix, and spatial variations in the structure of the polymer matrix will also be examined and compared with existing theories. Results from this award will be disseminated to industrial practitioners through an annual symposium organized by the researchers. In addition, the research team will lead hands-on demonstrations of nanoscience for the public at Philly Materials Day and the University of Pennsylvania's annual Nano Day.This award will support research to measure nanoparticle diffusion in hydrogels and entangled polymer melts that are characterized by their mesh size and tube diameter, respectively. The research will explore systems where the nanoparticle diameter and mesh size or tube diameter are comparable, because models predict strong deviations from conventional Stokes-Einstein diffusion in these cases. Single particle tracking methods will be used to measure nanoparticle diffusion in tetra-poly(ethylene oxide) and polyacrylamide hydrogels. Tetra-poly(ethylene oxide) hydrogels form a model network with nearly monodisperse mesh size. Polyacrylamide hydrogels form a network with a mesh size and heterogeneity that can be manipulated by varying solvents. Rutherford Backscattering Spectrometry will be used to measure nanoparticle diffusion coefficients for phenyl-capped, brush grafted, and hydroxyl-terminated nanoparticles (spherical and cylindrical) in polystyrene and poly(2-vinylpyridine) to explore both athermal and attractive nanoparticle-polymer interactions. Quantitative comparisons will be made with models and theories across a critical range of the ratio of nanoparticle to mesh size, as defined as the tube diameter in the reptation model. Finally, one nanoparticle-polymer system has been specially designed to facilitate measuring nanoparticle diffusion by both single particle tracking and Rutherford backscattering methods to compare complementary information provided by individual nanoparticle motion and ensemble averages from a single system.