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The composition of low-Tg n-butylacrylate-block-(acetoxyaceto)ethyl acrylate block polymers is investigated as a strategy to tune the properties of dynamically cross-linked vinylogous urethane vitrimers. As the proportion of the cross-linkable block is increased, the thermorheological properties, structure, and stress relaxation evolve in ways that cannot be explained by increasing cross-link density alone. Evidence is presented that network connectivity defects such as loops and dangling ends are increased by microphase separation. The thermomechanical and viscoelastic properties of block-copolymer-derived vitrimers arise from the subtle interplay of microphase separation and network defects.
Bibliographical noteFunding Information:
This work was supported by the NSF Center for Sustainable Polymers, CHE-1901635, and a seed grant from Northwestern’s Center for Engineering Sustainability and Resilience. This work made use of the Integrated Molecular Structure Education and Research Center at Northwestern which has received support from the NIH (S10-OD021786-01); the NSF (NSF CHE-9871268); Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); and the State of Illinois and International Institute for Nanotechnology. Rheological measurements were performed at the Materials Characterization and Imaging Facility, which receives support from the MRSEC Program (NSF DMR-1720139) of the Materials Research Center at Northwestern University. Also used was the Keck-II facility of NU’s NUANCE Center, which has received support from the SHyNE Resource, the MRSEC program at the Materials Research Center; the IIN, the Keck Foundation, and the State of Illinois, through the IIN. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program (DMR-2011401). This work used the 5-ID-D beamline of the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by E. I. DuPont de Nemours & Co., and The Dow Chemical Company, and State of Illinois funding to Northwestern University. This research used resources of the APS, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract no. DE-AC02-06CH11357. Eliot F. Woods is acknowledged for his assistance collecting and analyzing DOSY data.
© 2021 American Chemical Society.
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- Period 2
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- 1 Active
9/1/20 → 8/31/26
Project: Research project