| NSF Org: |
DMR Division Of Materials Research |
| Recipient: |
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| Initial Amendment Date: | February 10, 2017 |
| Latest Amendment Date: | February 10, 2017 |
| Award Number: | 1708999 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Andrew Lovinger
alovinge@nsf.gov (703)292-4933 DMR Division Of Materials Research MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | September 1, 2017 |
| End Date: | August 31, 2021 (Estimated) |
| Total Intended Award Amount: | $399,127.00 |
| Total Awarded Amount to Date: | $399,127.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
302 BUCHTEL COMMON AKRON OH US 44325-0001 (330)972-2760 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
170 University Ave Akron OH US 44320-3909 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | POLYMERS |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
NON-TECHNICAL SUMMARY:
About 70 % of industrial plastics are made of semicrystalline polymers, which have the ability to crystallize when processed industrially. The inherent nature of polymer molecules, consisting of very long molecular chains, leads to a highly complex hierarchy of structures in the solid state. The ability to control these hierarchical structures significantly influences mechanical and thermal properties of the resulting materials. Thus, semicrystalline polymers are used in a wide variety of applications including packaging, textiles, automobile, airplane parts, energy, biocompatible materials, and others. To further improve properties of semicrystalline polymers, it is necessary to understand their detailed structures in the solid state as well as the mechanisms of structural formation at the molecular level. This project focuses on fundamental understanding of molecular-level structures of semicrystalline polymers in samples crystallized in various controlled ways, and may lead to predictions of improved properties for commercially available polymeric materials. The PI will use novel magnetic resonance techniques to probe the molecular trajectory of polymer chains in the solid state of such polymer materials. This information will provide unprecedented detail about the molecular morphology of polymers and the interconnections among crystals, and would have implications on their mechanical properties. This project will also include advanced scientific training of graduate students in technologically important areas. They will experience a wide range of polymer research covering polymer synthesis, crystallization, advanced instrumentation, and molecular dynamics simulations. The research results will be reported in scientific journals and presented by the PI and students at national scientific meetings.
TECHNICAL SUMMARY:
Polymer crystallization induces structural changes of polymer molecules from random coils to folded chains in thin crystals. The mechanism of crystallization has been theoretically and experimentally studied in many publications over the past several decades. However, no decisive conclusion has been reached regarding the crystallization mechanism and chain-level structure. The PI has developed advanced techniques for 13C-13C double quantum (DQ) NMR combined with selective isotopic 13C labeling. Using these together with spin-dynamics simulation enables determination of the re-entrance sites of folded chains, the adjacent re-entry fraction, the successive folding number of semicrystalline polymers in the bulk and in solution-grown single crystals as a function of crystallization temperature. These experiments shed light on the extent of adjacent re-entry of polymer chains in solution-grown and bulk materials, the formation of three-dimensional nanostructures, and the effect of crystallization kinetics on the extent of chain folding. These aspects can be correlated with bundle and aggregation models and recent molecular dynamics simulation results. The planned experiments will further investigate the effects on chain trajectory in crystalline regions for a variety of important parameters including i) molecular weight, ii) polymer concentration, iii) solvent-polymer interactions, iv) confined spaces, v) entanglements, and vi) melt-memory. Such studies will provide detailed crystallization mechanisms of flexible semicrystalline polymers while contributing to the advanced training of students in technologically important areas.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
2/3 of polymers are semicrystalline. Our daily life highly replies on various semicrystalline polymers due to their excellent mechanical and thermal properties, low-cost production, and low mass. To maximumly gain polymer properties, detailed analysis of polymer structures and understanding crystallization mechanisms are necessary. However, it is challenging to characterize chain-level structure of synthetic polymers due to low chemical and structural contrasts (polymer is consisting of repeating monomer units). Therefore, there are long-standing debates in crystallization mechanism of long polymer chains at the molecular level. This project aims at establishing basic foundations of polymer crystallization at the molecular levels. To overcome analytical difficulty of synthetic polymers, solid-state NMR spectroscopy is applied to polymer systems through magnetic interactions. 13C isotope labeling technique and magnetic interactions were used to unravel chain trajectory for 13C labeled polymers. This technique does not require specific morphology, molecular weight and polydispersity, and crystallization conditions. Therefore, it can be applied to a broad range of experimental scopes in polymer crystallization. Following results were obtained: i) Chain-folding structure is independence of crystallization kinetics and molecular weight (Mw)s well above entanglement length (Me) in both solution- and melt-grown crystals. ii) Polymer concentration significantly lowers down chain-folding number. iii) Polymer chains adopt folded three-dimensional clusters in the solution-grown crystal. iv) Polymer chains fold prior to crystallization in the highly condensed state. v) High Mw sample gives higher adjacent re-entry number than relatively low Mws samples across Me. Through these experimental results, it was concluded that polymer chains fold prior to crystallization in highly condensed state and entanglement is the key factor to induce chain-folding in the melt grown crystals. Moreover, it was indicated that morphological change driven by kinetics is attributed to aggregation process of nano-building blocks in the solution-grown crystals. Furthermore, a new project for sustainable polyolefins was initiated. Unique molecular dynamics and crystallization behaviors for configurationally and conformationally disordered polymer crystal were reported. Finally, it was found that configurationally disorder crystal co-crystallizes with configurationally ordered crystals and change their crystalline structure and melting temperatures. Co-crystallization of novel polyolefins may be used as potential polyolefins for sustainability.
Through this four-year project, 1 PhD student completed his PhD thesis and got industry job related to polymer research. 2 PhD students have completed their fourth- and third-years research. Their research is going well. Through the project, 7 publications, 2 book chapters, 1 book, and 10 invited talks were provided by the PI and his group. 2 manuscripts are currently under review.
Last Modified: 12/30/2021
Modified by: Toshikazu Miyoshi
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