Effect of Chemical Structures on the Mechanical Properties of Slide-ring Gels

Abstract

Polymer network in slide-ring gels consists of cyclic molecules and their dimers threaded with polymer chains end-capped. Polymer chains do not bind each other covalently, but topologically connected via the figure-of-eight shaped cross-links. Therefore, polymer chains in slide-ring gels can slide through the cross-links. As the result of chain sliding, slide-ring gels exhibit unique mechanical properties. In addition, a peculiar non-linear pressure-responsive permeability of solvents was found recently. Slide-ring gel is synthesized by cross-linking of a necklace-like mechanically-interlocked polymer, so-called polyrotaxane. For the first decade of slide-ring gels, the network structures, mechanical properties, and various functionalization have been studied intensively by using a single-species polyrotaxane. However, we have recently developed the synthesis of polyrotaxanes to diversify the chemical structures of slide-ring gels, with different backbone polymers, cyclic components, and the ratios of these two components. Here we outline a peculiar viscoelastic property in slide-ring gels found recently, and then introduce several molecular designs on polyrotaxanes for controlling the mechanical properties of slide-ring gels.