Validation of the CoGEF Method as a Predictive Tool for Polymer Mechanochemistry
The development of force-responsive molecules called mechanophores is a central component of the field of polymer mechanochemistry. Mechanophores enable the design and fabrication of polymers for a variety of applications ranging from sensing to molecular release and self-healing materials. Nevertheless, an insufficient understanding of structure–activity relationships limits experimental development, and thus computation is necessary to guide the structural design of mechanophores. The constrained geometries simulate external force (CoGEF) method is a highly accessible and straightforward computational technique that simulates the effect of mechanical force on a molecule and enables the prediction of mechanochemical reactivity. Here, we use the CoGEF method to systematically evaluate every covalent mechanophore reported to date and compare the predicted mechanochemical reactivity to experimental results. Molecules that are mechanochemically inactive are also studied as negative controls. In general, mechanochemical reactions predicted with the CoGEF method at the common B3LYP/6-31G* level of density functional theory are in excellent agreement with reactivity determined experimentally. Moreover, bond rupture forces obtained from CoGEF calculations are compared to experimentally measured forces and demonstrated to be reliable indicators of mechanochemical activity. This investigation validates the CoGEF method as a powerful tool for predicting mechanochemical reactivity, enabling its widespread adoption to support the developing field of polymer mechanochemistry. Secondarily, this study provides a contemporary catalog of over 100 mechanophores developed to date.
Additional Information© 2020 American Chemical Society. Received: June 25, 2020; Published: September 9, 2020. Funding from Caltech and the Dow Next Generation Educator Fund is gratefully acknowledged. I.M.K. was supported by an NSF Graduate Research Fellowship (DGE-1745301). We also thank the Caltech-Cambridge Exchange Program (D.P.K.) and the Summer Undergraduate Research Fellowship Program at Caltech (N.J.C.) for financial support, and Stephen Craig for helpful discussion. Author Contributions. I.M.K. and C.C.H. contributed equally. The authors declare no competing financial interest.
Supplemental Material - ja0c06868_si_001.pdf