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Mechanochemically Active Polymers

Nancy Sottos's picture

Mechanochemical transduction enables anextraordinary range of physiological processes, including the sense of touch,hearing, balance, muscle contraction, as well as growth and remodeling of tissue and bone. While biology is replete with examples of active materials systems that respond to mechanical stimuli, synthetic analogs in bulk polymersare rare and have limited functionality. In a recent publication (Davis et al.,Nature, 459, 68-72, 2009), we report the rational, molecular design of solid-state polymeric materials where mechanical stress alone initiates a chemical reaction that provides assessment of the stress state prior to failure. These mechanoresponsive synthetic polymeric materials are created through a powerful, molecular based strategy, whereby force-activated mechanophores are linked directly into or serve as cross-links between polymer chains in bulk polymers. A mechanophore that changes colour as it undergoes a reversible electrocyclic ring-opening reaction under tensile stress allows us to directly visualize the mechanochemical reaction. Pronounced changes in colour and fluorescence emerge with the accumulation of plastic deformation, indicating that in these polymeric materials the transduction of mechanical force into the ring-opening reaction is an activated process. We anticipate that force activation of covalent bonds can serve as a general strategy for the development of new mechanophore building blocks that impart polymeric materials with desirable functionalities ranging from damage sensing to fully regenerative self-healing.  For more information:  http://autonomic.beckman.illinois.edu/Nature_Force2.html

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