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Overview | New Macromolecular Architectures | Self-Healing Polymers | Mechanochemistry | Photoresponsive Colloids | |
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Research Self-Healing Polymers
To date self-healing materials systems have largely focused on restoring functions such as mechanical properties of structural composites and barrier properties of protective coatings. We will continue to pursue chemistry for damage repair of materials under a wide range of conditions including high temperature. The self-healing concept based on release of liquid content from microcapsules is a general one to restore materials functionality such electrical conductivity in damaged electronics. For example, in order to overcome the cycle life and the safety issues that plague lithium-ion battery technology, new approaches are needed that can stabilize the electrode-electrolyte interface and restore electrodes degraded by microcracks formed from charge-discharge recycling. Toward this goal, we are developing new types polymer nanocomposite in which precursor materials such as carbon nanotubes (CNTs) are suspended in organic solvents encapsulated within polymer-based microcapsules. Shells that erode under conditions of high electrical potential, temperature spikes, mechanical damage or other appropriate stimuli could release these suspensions and deliver conductive components where they are needed, thus restoring current in damaged electrical conductors (Figure 2). The migration of CNTs in an organic solvent in driven by an external electrical field has been previously reported, suggesting that triggered release of CNT from microcapsules suspensions – even at small CNT weight fraction – could indeed provide an autonomous mechanism of self-repair of electronic functionality. Given recently obtained promising results, we intend to pursue this system further during the coming year. We plan to investigate variations on the encapsulation process including the use of ultrasound to produce submicron capsules. We will test the ability to encapsulate other components including nanoparticles and carbon-rich molecular fragments that may undergo electric field triggered nanowire self-assembly. Finally we plan to develop capsules that trigger the release of their contents to various stimuli. In addition to mechanical damage, triggered release by thermal and electrical conditions would be beneficial to self-healing batteries. We plan to design microcapsules with smart shell walls that can erode electrochemically and this exhibit electrical potential-triggered release of contents. Our self-healing research is done in collaboration with the Autonomous Materials Systems division of the Beckman Institute at the University of Illinois.
Representative Publications
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