Observation of pulley effect of slide-ring gel using atomic force microscopy

The slide-ring gel is a new kind of gel in which polymer chain can pass through topological crosslinks named figure-of-eight cross-links. Therefore, the polymer chains freely pass through the cross-links, which is supposed to automatically equalize the nanoscopic heterogeneity in structure and stress. In this study, we tried to observe single molecular pulley effect using atomic force microscopy (AFM). We introduce thiol groups on figure-of-eight cross-links and pulled the cross-links with Au-coated AFM cantilever. The maximum extension force was almost independent of the amount of thiol groups on crosslinks and of the frequency of Au-thiol bond formation. It was found that the averaged extension length of slide-ring gel in good solvent is much longer than that in poor solvent. This indicates that the pulley effect equalized the nanoscopic stress in slide-ring gel.