This is a collaborative research project involving a partnership between the University of Illinois at Urbana-Champaign, Cornell University, and PPG Industries. It will develop polymers that utilize changes in stress state to mechanically activate -- without human intervention -- chemical reactions that signal the presence of damage and initiate repair wherever and whenever it occurs. The reduction in waste achieved through lifetime extension will contribute to a sustainable materials landscape. Mechanoresponsive polymers are created by directly linking force-activated molecules (mechanophores) into polymer chains. The complex spatial and temporal changes in stress state that precede damage in polymeric materials promote mechanophore activation, transforming it into a new chemical species for signaling or for initiating productive changes in materials properties. Realization of mechanochemically based sustainable polymers requires mechanophore motifs with amplified responses that can be activated efficiently. The proposed research entails synthesis of new mechanophores specifically for damage detection and repair, experimental and computational development of force-focusing strategies to achieve efficient force transmission to the mechanophore, and experimental evaluation of materials systems. Elucidating the fundamental, molecular-level mechanisms governing mechanophore response to macroscopic damage in polymers will be advanced through symbiotic combination of modeling and experiments. These scientific advancements will then be applied to the design and experimental evaluation of polymers that self-report and self-heal in response to tension overload, fatigue, and interfacial delamination.
Waste reduction is key to a sustainable materials landscape. Plastics are ubiquitous industrial materials and their waste reduction is achievable through life extension and recycling. Given the high energy requirements, financial cost, and limited yield of plastic recycling, life extension is critically important to life cycle management. The proposed research program seeks to develop graded warning and healing systems for industrially relevant plastics. The technical approach relies on the synthesis of plastics with force sensitive molecular units called mechanophores that are activated by damage. Advances in self-reporting plastics will reduce material consumption and waste by eliminating prescheduled replacements. Self-healing capabilities for plastics can drastically extend the service lifetime of these materials. This research project will involve the education and training of several graduate students at the University of Illinois and Cornell University. These students will be part of an interdisciplinary research team working in close partnership with PPG Industries, Inc. to translate scientific advances to commercially viable plastics. The research themes of self-reporting and self-healing for sustainability provide a unique opportunity for education and outreach to the general public. A series of educational demonstrations, exhibits, and videos will be developed on how materials impact sustainability, with emphasis on zero waste. These platforms will be widely disseminated over the web and at special public engagement events.