Soft Mechanochemistry of Disulfide-Crosslinked Polymer Networks

Mechanochemistry harnesses mechanical force to facilitate chemical reactions. Traditionally, the field of polymer mechanochemistry has used methods to activate chemical bonds, which use forces that are larger than those that are required to break a covalent bond. The effect of weaker forces, which are known to play important roles in mechanobiology, has so far been largely overlooked in polymer mechanochemistry. This subdomain of mechanochemistry, which we like to refer to as soft mechanochemistry , is exemplified by degrafting of polymer brushes. There is also evidence that indicates that soft mechanochemical effects impact the properties of crosslinked polymer networks, but very little work has been done so far to systematically investigate and understand these phenomena. Swelling is a widespread phenomenon encountered in polymer materials, governed by intricate interactions between the polymer and the surrounding solvent at a molecular level. These interactions have been extensively explored, both theoretically and experimentally, to comprehend the underlying mechanisms. When solvent-polymer interactions are favorable, they result in the solvation of polymer chains. Solvation is believed to lead to tension acting on polymer chains and thus accelerate certain reactions, as has already been observed, for example, by the swelling-induced degrafting of polymer brushes. This work aims to extend such a conclusion from a two-dimension polymer brush to a three-dimensional polymer network. The correlation between swelling and swelling-induced degradation is built and furthermore, the differences between macroscopic and microscopic level is also discussed.