Materials World Network: In-Situ NMR Studies of Processing and Deformation of Polymer/Clay Nanocomposites

聚合物/层状硅酸盐(PLS)纳米复合材料的发现是近年来材料科学的一个重大发展。我们知道从各种各样的起始配方可以形成什么类型的形貌，以及这些纳米复合材料表现出什么样的性质。然而，对于纳米复合材料在加工过程中如何达到其特征形态，以及这些结构在大规模形变下的行为如何，人们知之甚少。完成全面建模所需的这些知识可以通过进行纳米复合材料加工和变形的现场研究来提供。这个材料世界网络团队使用原位核磁共振(核磁共振)技术研究这个话题。该团队由来自佐治亚理工学院的Johannes Leisen和Haskell Beckham与莱布尼茨聚合物研究所(德国德累斯顿)的Ulrich Scheler合作组成，他们在固态核磁共振和聚合物科学方面具有专业知识，在流变学-核磁共振方面具有专业知识。佐治亚理工学院小组进行变形研究，莱布尼茨小组进行加工研究。利用合成的氟碳纳米填料制备了聚丙烯/聚对苯二甲酸乙二酯纳米复合材料。利用各种先进的固体核磁共振方法对这些复合材料进行了单轴变形，重点考察了基质聚合物和纳米填料界面处的形态和动态变化。同时，使用高温流变仪对这些材料进行剪切下的核磁共振检查，重点是流动模式的演变(例如，剪切诱导的有序化)、填料分散和分子迁移率的调节。这些研究的结果有望大大加强我们对在技术相关的工艺条件下偏最小二乘法纳米复合材料的结构/性能关系如何演变的理解。有了这些知识，可以高效、低成本地开发出性能优越的新型偏振光纳米复合材料。本文的研究对致力于制造偏振光纳米复合材料的新兴行业具有广泛的意义。国外对偏最小二乘纳米复合材料的研究十分深入。因此，拟议中的研究将有助于提高美国在这一新兴领域的竞争力。这项研究的国际方面为相关研究生提供了一种独特的学习体验，为他们提供了在伙伴国进行长期研究的机会。该奖项是与国际科学与工程办公室共同资助的。

The discovery of polymer/layered silicate (PLS) nanocomposites has been a major recent development in materials science. We know what types of morphologies can be formed from a large variety of starting recipes, and what kinds of properties these nanocomposites exhibit. However, relatively little is known about how nanocomposite morphologies reach their characteristic forms during processing, nor how these structures behave under large-scale deformation to fracture. This knowledge, which is needed to complete comprehensive modeling, can be provided by conducting in-situ studies of nanocomposite processing and deformation. This Materials World Network team examines this topic using in-situ nuclear magnetic resonance (NMR) techniques. The team consists of Johannes Leisen and Haskell Beckham from the Georgia Institute of Technology, with expertise in solid-state NMR spectroscopy and polymer science, in partnership with Ulrich Scheler of the Leibniz Institute for Polymer Research (Dresden, Germany), with expertise in rheological-NMR. The Georgia Tech group conducts the deformation studies while the Leibniz group conducts the processing studies. PLS nanocomposites based on polypropylene and poly(ethylene terephthalate) are prepared using a synthetic fluoromica nanoscopic filler. These PLS nanocomposites are examined by a variety of advanced solid-state NMR methods while under uniaxial deformation, with an emphasis on the morphological and dynamical changes occurring at the interface between matrix polymer and nanoscopic filler. Simultaneously, these materials are examined by NMR under shear using high-temperature rheo-NMR, with an emphasis on flow-pattern evolution (e.g., shear-induced ordering), filler dispersion, and modulation of molecular mobilities. Findings from these studies are expected to significantly enhance our understanding of how the structure/property relationships in PLS nanocomposites evolve under technically relevant processing conditions. With this knowledge, new PLS nanocomposites with superior properties can be developed efficiently and cost-effectively.The proposed research has broad implications for an emerging industry devoted to manufacturing of PLS nanocomposites. Research in the field of PLS nanocomposites is pursued strongly overseas. The proposed research will therefore contribute toward the competitiveness of the U.S. in this emerging field. The international aspect of this research offers a unique learning experience for the involved graduate students by offering them the opportunity of extended research stays in the partner country.This award is co-funded with the Office of International Science and Engineering.