AFM observation of elongation-induced structures in slide-ring gels

The slide-ring gel has topological crosslinks ("figure-of-eight crosslinks") freely movable in polymer network. Inside the slide-ring gel, the structural and stress nonuniformity on the swelling or volume change is homogenized due to the "pulley effect" of the crosslinks. However, in poor solvent, nanoscale structural heterogeneity is induced by elongation; the pulley effect is disabled because of the aggregation of cyclodextrin molecules that constitute the figure-of-eight crosslinks. We visualized such structural heterogeneity in real space by AFM-based force mapping method. The obtained 2D stiffness map has characteristics consistent with the results of small angle X-ray scattering experiments.