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A crown ether–ammonium salt-type rotaxane monomer was synthesized in a high yield using dibenzo-24-crown-8-ether and sec-ammonium salt having a hydroxy terminal by means of an end-capping reaction with an ethynyl benzoic acid. Its N-acetylated derivative was also synthesized as a neutral monomer. Novel side chain-type polyrotaxanes, that is, ammonium-type and neutral polyphenylacetylenes tethering rotaxane moieties in side chains with high molecular weights were obtained in high yields by polymerizations with an Rh catalyst. N-acetylation of the rotaxane moieties of the ammonium salt-type polymer afforded a red-colored neutral polymer showing red-shifted UV-vis absorption due to the conjugated main chain, according to the change in distance between the wheel component and the polyacetylene main chain.

A series of novel fluorene-based cardo polycarbonates was synthesized by the anionic ring-opening polymerization of six-membered spirocyclic carbonate monomers. The polymers possessed a fluorene skeleton placed perpendicularly to the main chain. The polymerization of the fluorene monomers progressed according to their solubility in the reaction solvent. Interestingly, the fluorene pendant polycarbonates were obtained in sufficiently high molecular weights and in good yields, in spite of the fact that the monomers are structurally closely related to the diphenyl-substituted cyclic carbonate, which exhibited very low polymerizability. All obtained polymers showed favorable properties, including good solubility, amorphous nature, favorable thermal stabilities, remarkably low birefringence values and high refractive indices despite of the polymer consisting only of C, H and O atoms. The good potentiality in the application to optical materials was shown here.

Stimuli-degradable cross-linked polymers were developed by applying both topological linkage and size-complementarity of rotaxane to cross-link structure. Radical polymerization of a common vinyl monomer in the presence of the [3]rotaxane cross-linker gave the corresponding stable cross-linked polymer under ambient conditions. Anion exchange reaction with tetra(n-butyl)ammonium chloride caused the selective and efficient de-cross-linking of the cross-linked polymers to vinyl polymer and axle component of the cross-linker.

Poly[2]rotaxane and graft polyrotaxane were synthesized from a mixture of poly(crown ether) as a trunk polymer, boronic-acid-terminated secondary ammonium salt as an axle component and diol as an end-capping group by pseudorotaxane formation and subsequent catalyst-free dehydrative bondage between the boronic acid and the diol moieties. It turned out that the chemical stability of these supramolecular architectures primarily depends on the bulkiness of the diol group as the end-capping moiety and the inherence originating from the dynamic covalent bond of boronate.

Poly(m-phenylene diethynylene)s tethering a pendant rotaxane switch were synthesized. The reversible switching behavior of rotaxane in a polymer side chain matched that of the monomer. The dynamic foldamer behavior of these polymers was controlled by solvent and rotaxane moiety. The amine-type polyrotaxanes were confirmed to favor a folded conformation in a CH₂Cl₂/CH₃CN mixed solvent. In contrast, the ammonium salt-type polyrotaxanes exhibited only a random-coil conformation because of the ionic character in the same mixed solvent.