Controlling and Exploiting Spiropyran-based Mechanochromism
Meredith Barbee, Ph.D. candidate
Stephen Craig, advisor
Thursday, March 7, 2019 - 11:30am to 1:30pm
Location: French Family Science Center 2237
Avery, Meg

When synthetic materials experience mechanical deformation, polymer chains become highly strained, leading to bond scission and ultimately material failure. Work in the field of polymer mechanochemistry has coupled this tension to desired covalent chemical reactions to trigger constructive responses, including mechanochromism resulting from ring-opening of spiropyran to colored merocyanine.  Here, we present new findings on controlling and exploiting mechanochromism across multiple length scales from single molecules to bulk materials.  First, we utilize mechanochromism as an “at-a-glance” indicator prior to failure in stretchable electronics, creating a new avenue to empower user control of strain-dependent properties for future stretchable devices.  We also report the effect of substituents on the rate constants for ring-opening of spiropyran derivatives using single molecule force spectroscopy.  Applying a linear free energy relationship provides insight into the reaction mechanism under tension.  Finally, we observed the relative activation of these spiropyrans in a bulk material, allowing us to begin probing the molecular-level force distributions resulting from macroscopic deformation.