Validation of the CoGEF Method as a Predictive Tool for Polymer Mechanochemistry

Abstract

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.

Mechanically Triggered Release of Functionally Diverse Molecular Payloads from Masked 2-Furylcarbinol Derivatives

“…First, DFT calculations were performed on truncated models of each carbamate-functionalized mechanophore using the constrained geometries simulate external force (CoGEF) method, 36 which is a simple and reliable computational technique for predicting mechanochemical reactivity. 37 The mechanical elongation of each furan–maleimide adduct results in a predicted retro-[4 + 2] cycloaddition reaction to produce the expected furfuryl carbamate and maleimide fragments with nearly identical energy–displacement profiles ( Figure S6 ). The calculated rupture force ( F max ) is essentially the same regardless of substitution, which occurs at 4.0–4.1 nN and suggests similar mechanochemical activity of each mechanophore that is primarily dictated by pulling geometry.…”

Substituent Effects Control Spiropyran–Merocyanine Equilibria and Mechanochromic Utility

“…Recent theoretical work by the Walter group [41,51] has emphasized that mechanical bond breaking must consider temperature and loading rates, which yields rupture forces for SPs well below 1 nN and thus at least one order of magnitude smaller compared to other works in which these parameters are neglected. [15,52] In practical systems the situation is yet more complex. The force required for the SP→MC isomerization depends, besides molecular structure, on polymer architecture and morphology (which are interrelated).…”

“…Recent theoretical work by the Walter group [ 41,51 ] has emphasized that mechanical bond breaking must consider temperature and loading rates, which yields rupture forces for SPs well below 1 nN and thus at least one order of magnitude smaller compared to other works in which these parameters are neglected. [ 15,52 ]…”

Triggering Forces at the Nanoscale: Technologies for Single‐Chain Mechanical Activation and Manipulation

“…The length change was compared to a theoretical estimate, obtained from the quantum‐chemical method, “constrained geometries simulate external force” (CoGEF). [ 34 ] The authors found a theoretical elongation of about 1.05 nm, a value slightly shorter than the experimentally measured ones (1.2 or 1.4 nm). It is important to remark that, in Hartke and co‐workers’ work, from several thousand experiments only three force curves were related to the mechanophore's activation.…”