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A series of highly dielectric polyrotaxane derivatives consisting of axle polyethylene glycol (PEG) and threated α-cyclodextrins (CDs) were synthesized by modifying the hydroxyl groups of CDs with cyanoethyl or dicyanobutyl groups. We found that the introduction of poly(2-hydroxyethyl methacrylate) (PHEMA) side chain with a number of hydroxyl groups and subsequent cyanoethylation give particularly high dielectric constant (23.4), which is comparable to those of commercially available highly dielectric polymeric materials. We also succeeded in preparing a highly dielectric (e′ ∼ 16 at 10 kHz) and flexible (Young's modulus ∼ 3.4 MPa) elastomer film without any inorganic filler, which is a desirable material for insulator of dielectric elastomer actuators.

In this study, we have investigated molecular fluctuations in a liquid crystalline polyrotaxane (CB5PR) consisting of poly(ethylene glycol) (PEG) and α-cyclodextrins (CDs) chemically modified with mesogenic cyanobiphenyl groups in solid state by dielectric spectroscopy. The results were compared with a hydroxypropylated polyrotaxane (HyPR) without mesogens. CB5PR showed a high-frequency relaxation mode, δ-relaxation due to the rotation of mesogenic groups at high temperature, whereas such a mode was not observed for HyPR. It was found that the activation energy of the rotational mode of mesogenic groups in CB5PR was considerably less than that in conventional side chain liquid crystalline polymers (LCPs). This indicated that the mesogenic groups around the polymer backbone in a solid-state PR rotated more easily than those in conventional LCPs, because mesogens bonded to cyclic CD in CB5PR can rotate independently of the rotational motion of the axis PEG. On the other hand, both CB5PR and HyPR exhibited broader relaxation processes at a much lower temperature around the glass transition of PEG, which was ascribable to the local molecular fluctuation of PEG. Our experimental results suggested that the local fluctuation of PEG in a PR was barely affected by the interaction between PEG and cyclic molecules, independently of the side chains around CD. This decoupling behavior is consistent with the low activation energy of the δ-relaxation in CB5PR.

We investigated the structure, thermal properties, and dynamics of polyrotaxane (PR), composed of poly(ethylene glycol) (PEG) and α-cyclodextrins (CDs), and PR derivatives comprising hydroxypropylated CDs, that is, hydroxypropylated PRs (HyPRs), in the solid state by using wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and viscoelastic spectroscopy. It was observed that HyPRs with high chemical modification ratios show a WLF-type viscoelastic relaxation that can be ascribed to the cooperative segmental motion of several CD molecules, whereas HyPRs with a lower modification ratio and PR with a highly ordered packing structure of CDs do not exhibit any mechanical relaxation mode. A comparison between the relaxation temperatures of HyPRs with different modification and inclusion ratios suggested that the hydrogen bond between CDs primarily dominates the viscoelastic properties of solid-state PR. Our experimental results indicate a close relationship between the crystallinity and...

A novel side-chain liquid crystalline polyrotaxane (LCPR) whose mesogenic side chains can slide and rotate on the linear backbone was first developed. To obtain the LCPR, 6-(4‘-cyanobiphenyl-4‘ ‘-yloxy)hexanoyl chloride was prepared and reacted with a polyrotaxane consisting of α-cyclodextrin, poly(ethylene glycol) (Mw = 35 000), and adamantane end groups. The molecular characterization of the LCPR was performed with FT-IR, 1H NMR, and gel permeation chromatography analysis. Its phase structures and transitions were investigated by differential scanning calorimetry, wide-angle X-ray diffraction, and polarized light microscopy experiments. The experimental results shows that the LCPR has glass transition at 70 °C and mesomorphic−isotropic transition at 129 °C.

A new supramolecular system, liquid-crystalline polyrotaxane (LCPR), has been recently prepared by introduction of 4-cyano-4'-n-pentylbiphenyl (5CB) groups to the cyclic molecules of a polyrotaxane (PR) consisting of polyethylene glycol (PEG) and α-cyclodextrin (α-CD). Here we measured and compared the dielectric relaxations of PR and LCPR in solid state to investigate molecular motions of α-CD in PR and LCPR. It was found that PR exhibited a single relaxation mode while LCPR had two modes. These results suggested that the relaxation mode in PR would be due to the sliding fluctuation of α-CD along the axis chain and that the other mode in LCPR should arise from the rotational fluctuation of α-CD modified by 5CB.

We measured the electrical current-voltage characteristics of λDNA in vacuum using fine electrodes with a gap of about 200 nm. It was found that the electrical resistance of λDNA molecules between the fine electrodes had a large variation: from 7.8 MΩ to values larger than 1 TΩ. This was consistent with the controversial results given in previous reports. The temperature dependence of conductivity was explained well by the Arrhenius equation. In addition, the conductivity of a single molecule of double-stranded λDNA was measured by a “one-by-one” cutting method using atomic force microscopy (AFM). The conductivity was determined to be 3×10 1 S/cm, which is about the same order as that of semiconductors.