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

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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.