Polymer mechanochemistry by single-molecule force spectroscopy

It is critical to investigate the molecular mechanism of polymer mechanochemistry and force-induced structural transformation, and then establish the structure-mechanical property relationship of materials for the rational design and accurate preparation of force responsive polymer materials. However, due to the complexity of real material systems, it is difficult to accurately characterize these processes at the molecular level using traditional ensemble methods. Atomic force microscopy (AFM)-based single molecule force spectroscopy (SMFS) can manipulate a single polymer chain, which is an effective technique to study the mechanical properties and dynamics of a single molecule. In this review, we first focus on the basic concept, influencing factors, and recent progress of single-molecule mechanochemistry reactions of free polymer chains, from the strong covalent bond-based system to the coordination bond and hydrogen bond-based systems. Then, we discuss the application of AFM-SMFS technology in the single chain mechanical response of condensed systems, including the establishment of AFM-SMFS method for the study of polymer single crystals, and the exploration of the effect of factors such as chain composition, conformation, folding mode, and environment on the force-induced melting and nano mechanical properties. We hope that this review will attract further attention from the material, chemistry and computational research communities, and accelerate our understanding of the structure-property relationship of polymers.