Establishment of Self-assembled Rotaxane Ultrathin Film Chemistry

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Preparation of a self-assembled rotaxane monolayerSimple fabrication technique of a self-assembled rotaxane monolayer (rotaxane-SAM) consisting of a viologen-functionalized Alkanethiol and a-cyclodextrin (CD) using potential sweep has been established. Use of a pseudorotaxane to prepare the rotaxane-SAM often suffers with physical adsorption of excess CD molecules onto electrode surface that interferes with fabrication of the rotaxane-SAM. In contrast, use of the potential sweep for the pseudorotaxane method results in simple fabrication of the rotaxane-SAM because of desorption of the CD molecules form the electrode surface at negative potential.Synthesis and characterization of polyurethanes cross-linked with a rotaxaneThree polyurethanes (PU0, PU11 and PU33) containing azobis (dibenzo-24-crown-8 ether) 1 as a molecule for a mechanical bonding cross-link point with a [3]rotaxane structure except PU0 were synthesized. PU0 and PU11 were soluble in DMF and DMSO whereas PU33 swelled in both the solvents, suggesting that PU33 forms a 3D-network structure via the mechanical bonding cross-links. From the result of ATR-FT-IR measurements, introduction of 1 causes break of hydrogen bonds between urethane bond moieties as well as between carbonyl of urethane bond and ammonium unit in the PUs due to steric hindrance of 1 forming the [3]rotaxane structure. Thermal properties of the PUs revealed that specific heats of glass-transitions increased with increase in the content ratio of 1, suggesting that PU33 contains more amorphous region than PU0. PU33 showed no transition peaks after Tg, whereas PU11 gave the peaks for crystallization and melt. Thermal properties of glass-transition and melt for PU11 were also confirmed by dynamic viscoelastic property measurement.