| NSF Org: |
CHE Division Of Chemistry |
| Recipient: |
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| Initial Amendment Date: | October 26, 2016 |
| Latest Amendment Date: | October 26, 2016 |
| Award Number: | 1700847 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Lin He
lhe@nsf.gov (703)292-4956 CHE Division Of Chemistry MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | July 1, 2016 |
| End Date: | May 31, 2018 (Estimated) |
| Total Intended Award Amount: | $179,946.00 |
| Total Awarded Amount to Date: | $179,946.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
5801 S ELLIS AVE CHICAGO IL US 60637-5418 (773)702-8669 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
5640 S. Ellis Ave. Chicago IL US 60637-1433 |
| 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): | Macromolec/Supramolec/Nano |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
Prof. Stuart Rowan of the University of Chicago develops synthetic methods that allow access to new polymer architectures and studies how these architectures impact polymer properties. This research has potential societal benefit with regards to design and preparation of novel polymeric materials with desirable unique properties. The project involves graduate and undergraduate students, high school students from a local girl's high school, and students of under-represented groups from the inner city Cleveland Municipal School District (through the Envoys program). The integrated approach of this research provides students at all levels with an exciting learning environment and broad research experiences. In addition, Prof. Rowan and his research group design new demonstrations for the outreach program entitled "Natures Materials", which is part of the Cleveland Museum's "Winter Discovery Day" on Dr. Martin Luther King Jr. Day. This program aims (i) to expose the local community to polymers and how Nature's materials can help us create a sustainable planet, and (ii) to train current graduate students on how to communicate and educate the general public and younger students about science and technology.
This research project, which is supported by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, encompasses synthetic and metal-coordination chemistry, computational modeling, as well as polymer science and characterization. It focuses on the design, synthesis and characterization of polymers with doubly-threaded architectures where two chains are threaded through one macrocycle. The new synthetic methodology utilizes metal-ligand coordination as the thermodynamic driving force for the polymerization step and either dynamic covalent chemistry (in the form of ring closing metathesis) as the covalent fixing step to access the poly[n]catenanes or high yielding thiol-ene chemistry to access the doubly threaded poly[3]rotaxanes and slide ring gels. The polymers will have the ability to expand/contract without significantly altering bond or torsion angles and as such it is predicted they will exhibit unusual viscoelastic properties.
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.
Polymer architecture has a significant effect on the resulting physical properties of a material. For the first time we have been able to access a new class of polymer architecture, a poly[n]catenane, which consists solely of mechanically interlocked macrocycles (Fig a). The structure of a poly[n]catenane can be considered the molecular equivalent of a macroscopic chain, which, on account of its topological architecture, retains its flexibility no matter the stiffness of its components. Fig b shows the main conformational mobilities (rotational, elongational and rocking motions) in the backbone repeat unit of such a chain. Theoretical studies have suggested that poly[n]catenanes with such mobility elements possess unique entanglement characteristics and could exhibit a large loss modulus and a low activation energy for flow, and could potentially act as outstanding energy damping materials and/or elastomers with excellent toughness and stimuli-responsive mechanical properties. Our synthetic approach to these interesting materials is based a metallosupramolecular polymer (MSP) template that is formed by metal coordination of a macrocycle with a linear thread component (both of which contain two metal-binding sites). Once the templating step has been performed, the interlocked polymer can be accessed by a metathesis ring closing reaction of the thread component. The metal-free interlocked polymer is isolated in an overall good yield (ca. 75%) after demetallation. It was found that the product was a mixture of branched (24%), linear (60%) and cyclic (16%) poly[n]catenanes with an average of molecular weight (Mn) of ca. 21,000 g/mol. Data suggests that the largest branched poly[n]catenanes have as many as 130 interlocked rings. We have also demonstrated that the polymers are metallo-responsive (Fig c); indeed, linear poly[n]catenanes expand by ~70% upon metalation and these results agree very well with atomistic molecular simulations. We also conducted simulations to study the force-extension behavior of the metallated polymers, showing how the two different macrocycles contribute differently to the polymer properties.
Last Modified: 08/07/2018
Modified by: Stuart J Rowan
![Synthesis of Poly[n]catenanes](/por/images/Reports/POR/2018/1700847/1700847_10304176_1533653785099_FigureOutcomes--rgov-66x44.jpg)
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