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dc.contributor.advisorNiels Holten-Andersen.en_US
dc.contributor.authorLi, Qiaochu, Ph. D. Massachusetts Institute of Technologyen_US
dc.contributor.otherMassachusetts Institute of Technology. Department of Materials Science and Engineering.en_US
dc.date.accessioned2018-05-23T16:31:22Z
dc.date.available2018-05-23T16:31:22Z
dc.date.copyright2018en_US
dc.date.issued2018en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/115711
dc.descriptionThesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018.en_US
dc.descriptionCataloged from PDF version of thesis.en_US
dc.descriptionIncludes bibliographical references (pages 127-136).en_US
dc.description.abstractThe functional versatility and endurable self-healing capacity of soft materials in nature is found to originate from the dynamic supramolecular scaffolds assembled via reversible interactions. To mimic this strategy, extensive efforts have been made to design polymer networks with transient crosslinks, which lays the foundation for synthetic self-healing hydrogels. Towards the development of stronger and faster self-healing hydrogels, understanding and controlling the gel network dynamics is of critical importance, since it provides design principles for key properties such as dynamic mechanics and self-healing performance. For this purpose, a universal strategy independent of exact crosslinking chemistry would be regulating the polymer material's dynamic behavior by optimal network design, yet current understanding of the relationship between network structure and macroscopic dynamic mechanics is still limited, and implementation of complex network structure has always been challenging. In this thesis, we show how the dynamic mechanical properties in a hydrogel can be controlled by rational design of polymer network structures. Using mussel-inspired reversible catechol coordination chemistry, we developed a nanocomposite hydrogel network (NP gel) with hierarchical assembly of polymer chains on iron oxide (Fe3O4) nanoparticles as network crosslinks. With NP gel as a model system, we first investigated its unique dynamic mechanics in comparison with traditional permanent and dynamic gels, and discovered a general approach to manipulate the network dynamics by controlling the crosslink structural functionality. Then we further explored the underlying relationship between polymer network structure and two key parameters in relaxation mechanics, which elucidated universal approaches for designing relaxation patterns in supramolecular transient gel network. Finally, by utilizing these design principles, we designed a hybrid gel network using two crosslinking structures with distinct relaxation timescales. By simply adjusting the ratio of two crosslinks, we can precisely tune the material's dynamic mechanics from a viscoelastic fluid to a rigid solid. Such controllability in dynamic mechanics enabled performance optimization towards mechanically rigid and fast self-healing hydrogel materials.en_US
dc.description.statementofresponsibilityby Qiaochu Li.en_US
dc.format.extent136 pagesen_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsMIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectMaterials Science and Engineering.en_US
dc.titleDesigning dynamic mechanics in self-healing nanocomposite hydrogelsen_US
dc.typeThesisen_US
dc.description.degreePh. D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Materials Science and Engineering
dc.identifier.oclc1036986347en_US


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