Yoshiaki Nakamoto

Kanazawa University, Kanazawa-shi, Ishikawa-ken, Japan

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Publications (64)139.08 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We report transparent ion conductive ionic liquid-phenol resin hybrids prepared by in situ polymerization/crosslinking of phenol monomer in ionic liquid. As ionic liquid, we used highly ion conductive ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([EMI][TFSA]). Simultaneous polymerization and crosslinking of phenol with paraformaldehyde in [EMI][TFSA] yielded a highly transparent film. From a field emission scanning electron microscope (FE-SEM) image at 5000 magnification, the transparent hybrid prepared by in situ method did not show phase separation at 5000 magnification. In addition, from the FE-SEM image of the transparent hybrid at high magnification ( × 60 000), phenol resin and [EMI][TFSA] were observed to be integrated at a scale of a few nanometers. The transparent hybrid containing 20 wt% phenol resin showed high thermal stability and ionic conductivity (1.0 × 10−3 S cm−1 at 30 °C), which is comparable to the pristine ionic liquid [EMI][TFSA].
    Polymer Journal 02/2011; 43(4):421-424. · 1.50 Impact Factor
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    ABSTRACT: We monitored the progress of formation of dimethoxypillar[5]arene by size-exclusion chromatography. Surprisingly, the cyclization reaction completely finished in just 3 min. By improving the reaction conditions and purification process, we successfully obtained dimethoxypillar[5]arene in a short time and in high yield (71%) from commercially available reagents. By improving the deprotection reaction of the methoxy moieties, pillar[5]arene was isolated quantitatively. Single crystal X-ray analysis confirmed the structure of pillar[5]arene in the solid state.
    The Journal of Organic Chemistry 01/2011; 76(1):328-31. · 4.56 Impact Factor
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    ABSTRACT: We synthesized chiral-substituents modified pillar[5]arene for the first time. The chiral-substituents modified pillar[5]arene showed planar chirality and interconversion between (pS) and (pR) forms took place quickly. The planar chirality was switched by temperature, solvents, and addition of achiral guest. As the measurement temperature increased, the diastereomeric excess was decreased. The diastereomeric excesses were high in low-permittivity solvents, while a low diastereomeric excess was observed in high-permittivity solvents. Addition of achiral guest induced an increase of negative CD intensities.
    The Journal of Organic Chemistry 01/2011; 76(2):618-22. · 4.56 Impact Factor
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    ABSTRACT: The preparation of a hybrid of graphene oxide and per-6-amino-beta-cyclodextrin is reported. The hybrid formed a supramolecular graphene oxide polymer network upon addition of guest dimer.
    Chemical Communications 09/2010; 46(33):6087-9. · 6.38 Impact Factor
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    ABSTRACT: New polyrotaxane composed of pillar[5]arene and viologen polymer was successfully prepared with extremely high yield by capping the chain ends with adamantyl moieties. Pillar[5]arene and viologen polymer are soluble in various solvents such as acetone, acetonitrile, methanol, DMF, and DMSO, while the polyrotaxane was soluble in DMF and DMSO and insoluble in the other organic solvents. Formation of inter-molecular hydrogen bonds between the OH moieties of pillar[5]arenes stabilized the structure and reduced the solubility. The polyrotaxane exhibited a thermally induced color change from yellow to violet. On heating, the inter-molecular hydrogen bond became weakened, and the shuttling motion of pillar[5]arenes on the polymer axis was fast. Thus, efficient electron transfer from the electron donors of pillar[5]arenes to the electron acceptor of viologen polymer occurred in the whole polymer chain and the radical cation species were stabilized.
    Macromolecules. 08/2010;
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    ABSTRACT: The preparation and characterization of high-molecular weight diphenyl oxide- and diphenyl sulfide-novolacs are described. The polymerization of diphenyl oxide with 2 equivalence of formaldehyde proceeded to give the corresponding polymer (2) (Mn: 160,000, Mw/Mn: 29.1) in good yield. Further, an ultra high-molecular weight fraction (Mw > 1,000,000) was observed in the GPC trace of 2. The developed polymers can be considered as a new class of aromatic polymers that exhibit both novolac-like and engineering plastic properties and are thus promising compounds for material-engineering applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
    Journal of Applied Polymer Science 06/2010; 118(3):1651 - 1657. · 1.40 Impact Factor
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    ABSTRACT: A series of pillar[5]arene derivatives with alkyl groups of different length were synthesized. The new alkyl-substituted pillar[5]arene derivatives 1,4-bis(ethoxy)pillar[5]arene (C2), 1,4-bis(propoxy)pillar[5]arene (C3), 1,4-bis(butoxy)pillar[5]arene (C4), 1,4-bis(pentyloxy)pillar[5]arene (C5), 1,4-bis(hexyloxy)pillar[5]arene (C6), and 1,4-bis(dodecanoxy)pillar[5]arene (C12) were obtained by Lewis acid-catalyzed condensation of dialkoxybenzene monomers with paraformaldehyde. The conformational characteristics of the pillar[5]arene derivatives were investigated by dynamic (1)H NMR measurements. When the alkyl substituents were bulkier than methyl groups, the rotation of phenolic units in the pillar[5]arenes was suppressed and their conformation was immobilized. As their length increased, the alkyl substituents packed at the upper and lower rims and thus lowered the conformational freedom of the pillar[5]arenes.
    The Journal of Organic Chemistry 05/2010; 75(10):3268-73. · 4.56 Impact Factor
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    ABSTRACT: We report the direct synthesis of new functional novolacs having allyl ether (4) or bromoalkyl groups (5 and 6) in the side chain by the addition-condensation of allyl phenyl ether (1), 1-bromo-2-phenoxyethane (2) or 1-bromo-4-phenoxybutane (3) with formaldehyde. The structure of these novolacs was confirmed by Fourier transform infrared, 1H NMR and 13C NMR spectra. The number-average molecular weights (Mn) of the obtained polymers were found to be ~1000–3000. In the case of the polymerization of 1 with formaldehyde using hydrated sulfuric acid as a catalyst, Claisen condensation did not occur with the polymerization; therefore, pure allylated novolac (4) without a phenol moiety was obtained. Thus, in this process, phenol–formaldehyde condensation proceeded under such conditions that the functional group was not affected. These polymers (4–6) have considerable potential as reactive polymers in the field of materials science. Their applications are as follows: (i) a key reaction of a latent curing system: thermal stimuli-induced Claisen rearrangement of allylated novolac to generate phenolic hydroxyl groups; (ii) vinyl ether-modified novolac (7) prepared by 1-bromoethoxy-group-modified novolac; and (iii) an amphiphilic graft-shaped polymer prepared by bromoalkyl-group-modified novolac-initiated ring-opening polymerization of 2-methyl-2-oxazoline.Keywords: allyl phenyl ether; Claisen condensation; graft polymerization; novolac; phenolic resin; polycondensation; polymer reaction
    Polymer Journal 04/2010; · 1.50 Impact Factor
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    ABSTRACT: Water-soluble pillar[5]arene was synthesized by the introduction of carboxylate anions at both upper and lower rims. When cationic viologen salt was mixed with the water-soluble pillar[5]arene in aqueous media, a very stable 1:1 host-guest complex was formed.
    Chemical Communications 04/2010; 46(21):3708-10. · 6.38 Impact Factor
  • Macromolecules. 03/2010; 43(7).
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    ABSTRACT: A new nonsymmetric pillar[5]arene of ethoxymethoxypillar[5]arene (EMpillar[5]arene) has been synthesized. By 2D ROESY analysis of EMpillar[5]arene, the ethoxy and methoxy moieties were completely separated at the upper and lower rims, respectively. Moreover, by the variable-temperature (1)H NMR measurements of EMpillar[5]arene, the rotational movement of phenolic units in EMpillar[5]arene was slow on the NMR time scale or did not occur.
    Organic Letters 02/2010; 12(3):636-8. · 6.14 Impact Factor
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    ABSTRACT: The rotation behavior of the phenolic units in pillar[5]arenes has been studied by means of the dynamic 1H NMR measurements. In acetone-d6, the individual conformers of pillar[5]arene were observed under −60 °C, indicating that the rotation movement was slow on the NMR time scale under −60 °C. In permethylated pillar[5]arene in acetone-d6, the peaks were not split even at −90 °C, strongly suggesting that the rotation movement was fast on the NMR time scale at −90 °C. This is due to the lack of the intramolecular hydrogen bond belt in permethylated pillar[5]arene. In the mixture of pillar[5]arene and viologen guest in acetone-d6, the split peaks were found at −30 °C and did not change under −60 °C. By formation of the host−guest complex between pillar[5]arene and viologen guest, the rotation movement was slow on the NMR time scale under −30 °C and almost stopped under −60 °C.Keywords (keywords): pillar[5]arene; permethylated pillar[5]arene; intramolecular hydrogen bond belt; variable-temperature 1H NMR measurements; rotation; host−guest complex
    Journal of Physical Chemistry Letters - J PHYS CHEM LETT. 02/2010; 1(5).
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    ABSTRACT: We synthesized a novel alternating copolymer composed of calix[4]arene and calix[6]arene. Compared to the model compounds of calix[4]arene and calix[6]arene, the alternating copolymer strongly captured fluoranthene because of multipoint host–guest interactions between the calixarenes in the alternating copolymer and fluoranthene.
    Polymer Chemistry. 01/2010; 1(2).
  • Chemistry Letters - CHEM LETT. 01/2010; 39(4):422-423.
  • Macromolecules. 11/2009;
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    ABSTRACT: We report supramolecular assemblies of a beta-cyclodextrin dimer linked at both ends of a fluorescent phenylethynylpyrene moiety (Py-beta-CD dimer). The Py-beta-CD dimer formed supramolecular associations in aqueous media due to the pi-pi stacking of the hydrophobic phenylethynylpyrene moiety. From tapping mode atomic force microscopy measurements, the Py-beta-CD dimer formed wire-shaped assemblies in aqueous media. By adding sodium adamantane carboxylate to the supramolecular assemblies, the structural change to J-type assemblies was observed. In contrast, upon addition of the electron-deficient guest, the electron transfer from the electron rich phenylethynylpyrene moiety of the supramolecular assemblies to the electron-deficient guest took place.
    Langmuir 11/2009; 26(5):3169-73. · 4.38 Impact Factor
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    ABSTRACT: Pillar[5]arene from modified phenylethynyl groups was prepared; since the repeating pi-conjugated units were largely pi-delocalized via the through-space within the cavity, it showed temperature- and solvent-responsive blue-green emission.
    Chemical Communications 09/2009; · 6.38 Impact Factor
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    ABSTRACT: We report on synthesis, association behavior, and application of six-arm star-shaped and tadpole-shaped amphiphilic polyoxazolines from triphenylene initiators. We synthesized two kinds of novel triphenylene initiators: 2,3,6,7,10,11-hexa(6-bromohexyloxy)triphenylene (initiator for star-shaped polyoxazoline) and 2-(6-bromohexyloxy)-3,6,7,10,11-pentahexyloxytriphenylene (initiator for tadpole-shaped polyoxazoline). Ring-opening cationic polymerization of 2-methyl-2-oxazoline from these initiators successfully produced star- and tadpole-shaped polyoxazolines. Both the star- and tadpole-shaped polyoxazolines formed supramolecular associations in aqueous media due to π−π stacking of hydrophobic triphenylene moiety. Critical micelle concentrations (CMCs) and amounts of π−π stacking of the star- and tadpole-shaped polyoxazolines in aqueous media were investigated by 1H NMR and fluorescence measurements. From tapping mode atomic force microscopy (TM-AFM) measurements, the star-shaped polyoxazolines formed straight columnar stacks due to π−π stacking of hydrophobic disklike core of triphenylene moiety and symmetric star-shaped structure. In contrast, crooked nanowires were observed in the tadpole-shaped polyoxazoline. Tadpole shape was asymmetric, and thus ordered π−π stacking of hydrophobic triphenylene moiety was suppressed. Moreover, by using the columnar stacks of the star-shaped polyoxazoline as a template, we successfully synthesized wire-assembled gold nanoparticles.
    Macromolecules. 04/2009; 42(8).
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    ABSTRACT: In this study, a hydrophobic phospholipid polymer nano-dispersion was formed by self-aggregating poly(2-methacryloyloxyethyl phosphorylcholine-co-stearyl methacrylate) (PMS). Self-aggregation was carried out by diluting a PMS/polyol solution with hot water. The zeta potential of the PMS particles was changed by complexation with anionic or cationic surfactants, the addition of which did not affect the average diameter of the PMS particles, which was always less than 50 nm. The cationized PMS nano-dispersion was used for treating artificially damaged hair. An X-ray photoelectron spectroscopic analysis showed uniform adsorption of the PMS onto the surface of the hair specimens. The PMS nano-dispersion was not only adsorbed on the surface but also permeated into the hair, as shown by a fluorescence microscopic observation of the damaged hair treated with the PMS nano-dispersion that also contained Nile Red. From a scanning electron microscope observation, the PMS was also found to suppress the lift-ups of the hair cuticle. The surface of damaged hair was hydrophilic, whereas the one treated with PMS was hydrophobic, like healthy hair. PMS treatment has decreased the surface friction and electrostatic decay of damaged hair, and also prevented the discoloration of colored hair. Keywords: 2-methacryloyloxyethyl phosphorylcholine, phospholipid polymer, intercellular lipid, nano-dispersion, self-aggregation, zeta potential, damaged hair, surface friction, electrostatic decay, discoloration.
    International journal of cosmetic science 03/2009; 31(1):75.
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    ABSTRACT: Lewis acid-catalyzed condensation of 1,2- and 1,3-dimethoxybenzenes with paraformaldehyde afforded an ortho-bridged cyclic trimer (1) and a meta-bridged cyclic tetramer (2), respectively. Furthermore, condensation of 1,3,5-trimethoxybenzene with paraformaldehyde in the presence of Lewis acid catalyst successfully rendered the first dodecamethoxy-substituted calix[4]arene (3) with high yield. From X-ray crystallography, it was found that 3 formed the partial cone conformation. The conformational behavior of 3 in the solution was investigated by variable temperature 1H NMR measurements. The partial cone structure observed in the solid state was retained in the solution at low temperatures. Furthermore, because of the slow conformational exchanges of 3 on the NMR time scale, bimodal conformational exchanges were found. The host–guest property of 3 with the electron accepting guest, tetracyanoethylene (TCNE) was examined by UV–Vis measurements, and the ability to associate with the 3-TCNE complex was three times higher than that of the 2-TCNE complex. The observation is due to the superior electron donating property and slow conformational exchanges of 3 compared with those of analogous 2.Graphical abstractLewis acid-catalyzed condensation of 1,3,5-trimethoxybenzene with paraformaldehyde gave new dodecamethoxy-substituted calix[4]arene. It showed slow bimodal conformational exchanges on the NMR time scale and formed host–guest complexes with the electron acceptor.
    Tetrahedron. 01/2009; 65(51):10644-10649.

Publication Stats

316 Citations
139.08 Total Impact Points

Institutions

  • 1982–2011
    • Kanazawa University
      • • Graduate School of Natural Science and Technology
      • • Department of Chemical and Material Engineering
      Kanazawa-shi, Ishikawa-ken, Japan
  • 2006
    • Tokyo Institute of Technology
      • Organic and Polymeric Materials Department
      Tokyo, Tokyo-to, Japan