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进展。我们知道从各种各样的初始配方中可以形成什么样的形态，以及这些纳米复合材料表现出什么样的性质。然而，对于纳米复合材料的形态如何在加工过程中达到其特征形态，以及这些结构在大规模变形到断裂下的行为，人们知之甚少。完成综合建模所需的这些知识可以通过对纳米复合材料加工和变形的原位研究来提供。这个材料世界网络团队使用原位核磁共振（NMR）技术来研究这个主题。该团队由乔治亚理工学院的Johannes Leisen和Haskell Beckham组成，他们在固态核磁共振光谱和聚合物科学方面具有专业知识，与莱布尼茨聚合物研究所（德国德累斯顿）的Ulrich Scheler合作，他们在流变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。采用合成的荧光纳米填料制备了基于聚丙烯和聚对苯二甲酸乙酯的聚苯二甲酸乙酯纳米复合材料。这些PLS纳米复合材料在单轴变形下通过各种先进的固态核磁共振方法进行了检测，重点研究了基质聚合物和纳米填料之间界面的形态和动力学变化。同时，使用高温流变核磁共振在剪切下对这些材料进行了核磁共振检测，重点研究了流动模式演变（例如剪切诱导的有序）、填料分散和分子迁移率的调制。这些研究结果有望显著提高我们对PLS纳米复合材料在技术相关加工条件下结构/性能关系演变的理解。有了这些知识，新的具有优异性能的PLS纳米复合材料可以高效和经济地开发。提出的研究对致力于制造PLS纳米复合材料的新兴产业具有广泛的意义。国外对聚苯二甲酸乙二醇酯纳米复合材料的研究正在蓬勃发展。因此，拟议的研究将有助于美国在这一新兴领域的竞争力。这项研究的国际方面为参与研究的研究生提供了一个独特的学习经验，为他们提供了在合作伙伴国家进行长期研究的机会。该奖项与国际科学与工程办公室共同资助。

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.