Topological Gel

Various organic supramolecules with unique structures have attracted great interests of many researchers. We formed a novel kind of gel, i.e., topological gel, which has crosslinkages moving freely in a polymer network. In the topological gel, the polymer chains with bulky end groups are neither covalently cross-linked like chemical gels nor attractively interacted like physical gels, but are topologically interlocked by figure-of-eight cross-links. It is therefore expected that the figure-of-eight cross-links can pass the polymer chains freely to equalize the tension of the threading polymer chains just like pulleys. Therefore, the nanoscopic heterogeneity in structure and stress may be automatically equalized in the gel. On tensile deformation, the polymer chains in the chemical gel are broken gradually due to the heterogeneous polymer length between fixed cross-links. On the other hand, the polymer chain in the topological gel can pass through the figure-of-eight cross-links acting like pulleys to equalize the tension of the polymer chains cooperatively. The physical features of the topological gel such as high transparency, good tensibility, low viscosity and large swellability in water are supposed to mainly result from the pulley effect.