Organic−Inorganic Hybrid Slide-Ring Gels: Polyrotaxanes Consisting of Poly(dimethylsiloxane) and γ-Cyclodextrin and Subsequent Topological Cross-Linking

A novel polyrotaxane consisting of poly(dimethylsiloxane) (PDMS) and γ-cyclodextrin (γ-CD) is synthesized, and the threaded γ-CDs of polyrotaxane are intermolecularly cross-linked in solution to yield a new class of slide-ring gel. Synthesis of the polyrotaxane is achieved by an end-capping reaction of pseudo-polyrotaxane whose both ends are preliminarily activated as p-nitrophenyl ester with p-methoxytritylamine derivatives. The obtained polyrotaxane is soluble in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc) only in the presence of lithium salts, while PDMS itself is not soluble in these media. Characterization of the polyrotaxane is performed by NMR, FT-IR, and TGA, showing that it is sparsely populated with γ-CDs. Chemical modifications of γ-CDs of the polyrotaxane improve the solubility in various organic solvents and enable further characterizations. An acetylated polyrotaxane is measured by GPC in chloroform to verify the rotaxanation, showing increase of molecular weight and refract...