Professor Stephen Craig
Tuesday February 6, 2018
"Stretching the Limits of Chemical Reactivity Through Polymer Mechanochemistry”
The forces typical of the macroscopic world (for example, those between a baby's fingers) are many orders of magnitude larger than the forces between the individual atoms of a molecule. It has been known for decades, for example, that breaking a piece of plastic or shearing a polymer solution can lead to homolytic carbon-carbon bond scission along the main chain of an organic polymer and a concomitant reduction in molecular weight. The magnitude of macroscopic forces, in combination with the fact that they are directional, creates a spectacular opportunity to direct chemistry that might otherwise be effectively impossible.
This talk will present studies of reactions under large, directional forces, and their applications in studies of fundamental reactivity and new classes of stress-responsive polymers. Specific outcomes that have been observed include the ability to trap transition states for extended periods of time, molecules that get shorter in response to being pulled, and new classes of self-healing polymers in which mechanical activation of chemical reactions leads to improved structure and properties under conditions that are typically destructive to both. The emphasis will be on fundamental structure-activity relationships that provide insights into the challenges, opportunities, and strategies for next generation mechanochemical responses.
~Coffee/tea will be served prior to lecture~