Small-angle X-ray scattering study of the pulley effect of slide-ring gels

The structure of slide-ring (SR) gels in various types of solvents was investigated by small-angle X-ray scattering (SAXS). The SR gels have a unique characteristic called the pulley effect that the cross-links made of alpha-cyclodextrin molecules in a figure-eight shape can slide along the polymer chain. The SAXS results show that, in a poor solvent, the sliding cross-links form aggregates that prevent the pulley effect, while the polymer chains freely pass through the cross-links acting like pulleys in a good solvent. A vertically elliptic pattern was observed in two-dimensional SAXS profiles for covalent-bonded chemical gels in a good solvent under uniaxial horizontal deformation, while an isotropic profile was observed for the SR gels in a good solvent even under deformation. This difference in the deformation mechanism between the SR gels and the chemical gels supports the pulley effect of the SR gels.