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Norio Tsubokawa - One of the best experts on this subject based on the ideXlab platform.

  • Immobilization of capsaicin onto silica nanoparticle surface and stimulus properties of the capsaicin‐immobilized silica
    Journal of Polymer Science Part A: Polymer Chemistry, 2010
    Co-Authors: Takeshi Yamauchi, Kazuhiro Fujiki, Kumi Shirai, Tomoya Saitoh, Norio Tsubokawa
    Abstract:

    To prepare silica nanoparticle having biorepellent activity, the immobilization of capsaicin onto hyperbranched poly(amidoamine) (PAMAM)-grafted silica was investigated. Grafting of PAMAM onto a silica surface was achieved in a solvent-free dry system using PAMAM Dendrimer Synthesis methodology. The immobilization of capsaicin was achieved by the reaction of hydroxyl groups of capsaicin with isocyanate groups of Silica-PAMAM, which were introduced by the reaction of terminal amino groups of Silica-PAMAM with hexamethylene diisocyanate. The immobilization of capsaicin was confirmed by thermal decomposition GC-MS. The amount of capsaicin immobilized onto PAMAM-grafted silica was determined to be 0.10 mmol/g. Capsaicin-immobilized Silica-PAMAM (Silica-PAMAM-Cap) was dispersed uniformly in water and Tyrode solution. Stimulus activity of Silica-PAMAM-Cap was estimated using two stimulus tests, that is a magnus test and a paw licking test, to sensory nerve of mice. As the result of magnus test, it was found that the Silica-PAMAM-Cap shows stimulus activity. It was found that elution of capsaicin could be depressed by immobilizing capsaicin onto Silica-PAMAM from the result of paw licking test. In addition, the stimulus property of Silica-PAMAM-Cap to the human skin could be observed and it was found that Silica-PAMAM-Cap had acrid taste. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1800–1805, 2010

  • immobilization of flame retardant onto silica nanoparticle surface and properties of epoxy resin filled with the flame retardant immobilized silica
    Journal of Polymer Science Part A, 2009
    Co-Authors: Takeshi Yamauchi, Akira Yuuki, Kazuhiro Fujiki, Kumi Shirai, Gang Wei, Norio Tsubokawa
    Abstract:

    To prepare silica nanoparticle having flame retardant activity, the immobilization of flame retardant onto hyperbranched poly(amidoamine) (PAMAM)-grafted silica was investigated. Grafting of PAMAM onto a silica surface was achieved in a solvent-free dry-system using PAMAM Dendrimer Synthesis methodology. The immobilization of bromine flame retardant, poly(2,2′,6,6′-tetrabromobisphenol-A) diglycidyl ether (PTBBA), was successfully achieved by the reaction of terminal amino groups of PAMAM-grafted silica (Silica-PAMAM) with epoxy groups of PTBBA. The immobilization of PTBBA was confirmed by FTIR and thermal decomposition GC-MS. The amount of PTBBA immobilized onto Silica-PAMAM was determined to be 60 wt %. PTBBA-immobilized Silica-PAMAM (Silica-PAMAM-PTBBA) was dispersed uniformly in a epoxy resin, and the epoxy resin was cured in the presence of hexamethylenediamine. Flame retardant activity of the epoxy resin filled with Silica-PAMAM-PTBBA was estimated by limiting oxygen index (LOI). The LOI of epoxy resin filled with Silica-PAMAM-PTBBA was higher than that filled with untreated silica and free PTBBA. It was confirmed that the flame retardant activity of epoxy resin was improved by the addition of the Silica-PAMAM-PTBBA. The elimination of PTBBA from the epoxy resin filled with Silica-PAMAM-PTBBA into boiling water was hardly observed by immobilization of PTBBA onto silica surface. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6145–6152, 2009

  • Surface Grafting of Polymers onto Nanoparticles in a Solvent-Free Dry-System and Applications of Polymer-grafted Nanoparticles as Novel Functional Hybrid Materials
    Polymer Journal, 2007
    Co-Authors: Norio Tsubokawa
    Abstract:

    For the prevention of environmental pollution and simplification of reactions, scale-up Synthesis of polymer-grafted inorganic nanoparticles in a solvent-free dry-system is reviewed. The grafting of polymers onto nanoparticles in a solvent-free dry-system was achieved by spraying monomers onto nanoparticles having initiating group. After the reaction, unreacted monomer and by-products were removed under high vacuum. For example, grafting of hyperbranched poly(amidoamine) (PAMAM) was successfully achieved using Dendrimer Synthesis methodology in a solvent-free dry-system. The percentage of PAMAM grafting onto the nanoparticle surface was 141% with repeated reaction cycles of 8-times. In addition, radical graft polymerization of vinyl monomers onto silica nanoparticles was achieved by spraying the monomers onto silica nanoparticles containing azo and peroxycarbonate groups in a solvent-free dry-system. The formation of ungrafted polymer was depressed in comparison with graft polymerization in solution: the grafting efficiency was 90–95%. PAMAM-grafted silica dispersed uniformly in epoxy resin and has an ability to cure the epoxy resin. Glass transition temperature of cured material was much higher than that of the material cured by conventional curing agents. The immobilization of norbornadiene, capsaicin, and flame retardant onto PAMAM-grafted nanoparticle and the properties of the resulting materials are also described.

  • Preparation and Properties of Polymer-grafted Carbon Nanotubes and Nanofibers
    Polymer Journal, 2005
    Co-Authors: Norio Tsubokawa
    Abstract:

    Recent advances in surface grafting of polymers onto carbon nanotubes (CNT) and nanofibers, such as vapor grown carbon fiber (VGCF), are reviewed. The grafting of polymers onto these surfaces was achieved by (1) the “grafting onto” method, (2) “polymer reaction” method, (3) “grafting from” method, and (4) “stepwise growth” method by Dendrimer Synthesis methodology. For the grafting of polymers, surface functional groups, such as carboxyl and phenolic hydroxyl groups, previously introduced onto the surface by oxidation with nitric acid, were used as grafting sites. These functional groups were converted into various initiating groups and surface initiated graft polymerization was achieved. The graphene sheet (polycondensed aromatic rings) of CNT and VGCF were used as grafting sites by using ligand-exchange reaction with polymers containing ferrocene moieties. The radical trapping nature of CNT and VGCF surface was used for the grafting of polymers. Dispersibility in solvents for good solvents of grafted polymer was remarkably improved by the surface grafting of polymers onto CNT and VGCF surfaces. The response of electric resistance of the composite prepared from polymer-grafted CNT and VGCF to solvent vapor and temperature is discussed.

  • Scale-up Synthesis of hyperbranched poly(amidoamine)-grafted ultrafine silica using Dendrimer Synthesis methodology in solvent-free dry-system
    Polymers for Advanced Technologies, 2002
    Co-Authors: Masamichi Murota, Shimpei Sato, Norio Tsubokawa
    Abstract:

    Scale-up Synthesis of hyperbranched poly(amidoamine)-grafted ultrafine silica was successfully achieved by using Dendrimer Synthesis methodology in solvent-free dry-system. The poly(amidoamine) was allowed to grow from silica surface by repeating two steps: (1) Michael addition of methyl acrylate (MA) to amino group on the surface and (2) amidation of terminal ester group with ethylenediamine (EDA). MA was sprayed onto silica having amino group and the silica agitated at 300 rpm at 50 °C. After the reaction, unreacted MA was removed under vacuum. Then EDA was sprayed and the reaction was conducted at 50 °C with agitation. After the reaction, unreacted EDA was also removed under vacuum at 50 °C and MA was sprayed again. The percentage of poly(amidoamine) grafting onto the surface was determined to be 141% with repeated reaction cycles of eight-times. However, the value was considerably smaller than that of the theoretical value. This indicates that the propagation of poly(amidoamine) dendron from silica surface was not achieved theoretically and hyperbranched poly(amidoamine) was grafted onto the surface because of steric hindrance of grafted polymer. In addition, the effect of initial amino group content on the growth of poly(amidoamine) from the surface was investigated. It was concluded that the method is suitable for the scale-up Synthesis of hyperbranched poly(amidoamine)-grafted silica. Copyright © 2002 John Wiley & Sons, Ltd.

Christopher N. Bowman - One of the best experts on this subject based on the ideXlab platform.

  • click chemistry in materials science
    Advanced Functional Materials, 2014
    Co-Authors: Weixian Xi, Christopher J. Kloxin, Timothy F. Scott, Christopher N. Bowman
    Abstract:

    Despite originating only a little more than a decade ago, click chemistry has become one of the most powerful paradigms in materials science, Synthesis, and modification. By developing and implementing simple, robust chemistries that do not require difficult separations or harsh conditions, the ability to form, modify, and control the structure of materials on various length scales has become more broadly available to those in the materials science community. As such, click chemistry has seen broad implementation in polymer functionalization, surface modification, block copolymer and Dendrimer Synthesis, biomaterials fabrication, biofunctionalization, and in many other areas of materials science. Here, the basic reactions, approaches, and applications of click chemistry in materials science are highlighted, and a brief look is taken into the future enabling developments in this field.

  • spatial and temporal control of the alkyne azide cycloaddition by photoinitiated cu ii reduction
    Nature Chemistry, 2011
    Co-Authors: Brian J Adzima, Christopher J. Kloxin, Youhua Tao, Cole A Deforest, Kristi S Anseth, Christopher N. Bowman
    Abstract:

    The click reaction paradigm is focused on the development and implementation of reactions that are simple to perform while being robust and providing exquisite control of the reaction and its products. Arguably the most prolific and powerful of these reactions, the copper-catalysed alkyne-azide reaction (CuAAC) is highly efficient and ubiquitous in an ever increasing number of synthetic methodologies and applications, including bioconjugation, labelling, surface functionalization, Dendrimer Synthesis, polymer Synthesis and polymer modification. Unfortunately, as the Cu(I) catalyst is typically generated by the chemical reduction of Cu(II) to Cu(I), or added as a Cu(I) salt, temporal and spatial control of the CuAAC reaction is not readily achieved. Here, we demonstrate catalysis of the CuAAC reaction via the photochemical reduction of Cu(II) to Cu(I), affording comprehensive spatial and temporal control of the CuAAC reaction using standard photolithographic techniques. Results reveal the diverse capability of this technique in small molecule Synthesis, patterned material fabrication and patterned chemical modification.

  • Spatial and temporal control of the alkyne–azide cycloaddition by photoinitiated Cu(II) reduction
    Nature Chemistry, 2011
    Co-Authors: Brian J Adzima, Christopher J. Kloxin, Youhua Tao, Cole A Deforest, Kristi S Anseth, Christopher N. Bowman
    Abstract:

    The click reaction paradigm is focused on the development and implementation of reactions that are simple to perform while being robust and providing exquisite control of the reaction and its products. Arguably the most prolific and powerful of these reactions, the copper-catalysed alkyne–azide reaction (CuAAC) is highly efficient and ubiquitous in an ever increasing number of synthetic methodologies and applications, including bioconjugation, labelling, surface functionalization, Dendrimer Synthesis, polymer Synthesis and polymer modification. Unfortunately, as the Cu( I ) catalyst is typically generated by the chemical reduction of Cu( II ) to Cu( I ), or added as a Cu( I ) salt, temporal and spatial control of the CuAAC reaction is not readily achieved. Here, we demonstrate catalysis of the CuAAC reaction via the photochemical reduction of Cu( II ) to Cu( I ), affording comprehensive spatial and temporal control of the CuAAC reaction using standard photolithographic techniques. Results reveal the diverse capability of this technique in small molecule Synthesis, patterned material fabrication and patterned chemical modification. The copper( I )-catalysed azide–alkyne cycloaddition is arguably the most prolific and powerful example of the click reaction paradigm. Here, photochemical reduction of Cu( II ) allows spatial and temporal control over the reaction for small-molecule Synthesis, patterning of hydrogel formation and the in situ labelling of gels, with features as small as 25 micrometres being produced.

Mark Bradley - One of the best experts on this subject based on the ideXlab platform.

  • solid phase construction high efficiency Dendrimer Synthesis using ab3 isocyanate type monomers
    Tetrahedron, 2003
    Co-Authors: Sylvain Lebreton, Siew Eng How, Monika Buchholz, Boonek Yingyongnarongkul, Mark Bradley
    Abstract:

    Solid-phase Synthesis is an ideal tool for reactions that require high concentrations and excess reagents and forcing chemical conditions. One such chemistry is that required for Dendrimer construction. In this paper the Synthesis of a series of symmetrical AB(3) isocyanate-type monomers is reported and used for the preparation of tri-branched Dendrimers on the solid-phase. This method not only allows isolable Dendrimer but can generate high-loading supports and devices for multivalent presentation.

  • Solid-phase Dendrimer Synthesis
    Biopolymers, 1998
    Co-Authors: Neil J. Wells, Andrea Basso, Mark Bradley
    Abstract:

    Dendrimers are highly ordered, hyperbranched polymers with potential for a whole range of chemical applications. Solution-phase Synthesis of Dendrimers is often challenging, requiring long reaction times and nontrivial purification; solid-phase methodology, on the other hand, enables reactions to be driven to completion by using a large excess of reagents with trivial purification. In this paper we show that polyamidoamine Dendrimers may be synthesized conveniently and efficiently on a solid support, and that these molecules are of good homogeneity as characterized by 1H- and 13C-nmr and electrospray mass spectrometry. These solid-phase Dendrimers were used as a bead loading amplification tool in the Synthesis of a hexapeptide library (Xaa–Gly–Gly–Phe–Leu–Lys) to allow single bead analysis as well as allowing the efficient Synthesis of two Dendrimer conjugates (Leu–enkephalin–Lys and Chlorambucil). This demonstrated that peptides and small drug molecules can be grown directly onto the Dendrimer or onto a linker attached to the Dendrimer periphery, enhancing general Dendrimer utility. © 1999 John Wiley & Sons, Inc. Biopoly 47: 381–396, 1998

Edgar H H Wong - One of the best experts on this subject based on the ideXlab platform.

Takeshi Yamauchi - One of the best experts on this subject based on the ideXlab platform.

  • Immobilization of capsaicin onto silica nanoparticle surface and stimulus properties of the capsaicin‐immobilized silica
    Journal of Polymer Science Part A: Polymer Chemistry, 2010
    Co-Authors: Takeshi Yamauchi, Kazuhiro Fujiki, Kumi Shirai, Tomoya Saitoh, Norio Tsubokawa
    Abstract:

    To prepare silica nanoparticle having biorepellent activity, the immobilization of capsaicin onto hyperbranched poly(amidoamine) (PAMAM)-grafted silica was investigated. Grafting of PAMAM onto a silica surface was achieved in a solvent-free dry system using PAMAM Dendrimer Synthesis methodology. The immobilization of capsaicin was achieved by the reaction of hydroxyl groups of capsaicin with isocyanate groups of Silica-PAMAM, which were introduced by the reaction of terminal amino groups of Silica-PAMAM with hexamethylene diisocyanate. The immobilization of capsaicin was confirmed by thermal decomposition GC-MS. The amount of capsaicin immobilized onto PAMAM-grafted silica was determined to be 0.10 mmol/g. Capsaicin-immobilized Silica-PAMAM (Silica-PAMAM-Cap) was dispersed uniformly in water and Tyrode solution. Stimulus activity of Silica-PAMAM-Cap was estimated using two stimulus tests, that is a magnus test and a paw licking test, to sensory nerve of mice. As the result of magnus test, it was found that the Silica-PAMAM-Cap shows stimulus activity. It was found that elution of capsaicin could be depressed by immobilizing capsaicin onto Silica-PAMAM from the result of paw licking test. In addition, the stimulus property of Silica-PAMAM-Cap to the human skin could be observed and it was found that Silica-PAMAM-Cap had acrid taste. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1800–1805, 2010

  • immobilization of flame retardant onto silica nanoparticle surface and properties of epoxy resin filled with the flame retardant immobilized silica
    Journal of Polymer Science Part A, 2009
    Co-Authors: Takeshi Yamauchi, Akira Yuuki, Kazuhiro Fujiki, Kumi Shirai, Gang Wei, Norio Tsubokawa
    Abstract:

    To prepare silica nanoparticle having flame retardant activity, the immobilization of flame retardant onto hyperbranched poly(amidoamine) (PAMAM)-grafted silica was investigated. Grafting of PAMAM onto a silica surface was achieved in a solvent-free dry-system using PAMAM Dendrimer Synthesis methodology. The immobilization of bromine flame retardant, poly(2,2′,6,6′-tetrabromobisphenol-A) diglycidyl ether (PTBBA), was successfully achieved by the reaction of terminal amino groups of PAMAM-grafted silica (Silica-PAMAM) with epoxy groups of PTBBA. The immobilization of PTBBA was confirmed by FTIR and thermal decomposition GC-MS. The amount of PTBBA immobilized onto Silica-PAMAM was determined to be 60 wt %. PTBBA-immobilized Silica-PAMAM (Silica-PAMAM-PTBBA) was dispersed uniformly in a epoxy resin, and the epoxy resin was cured in the presence of hexamethylenediamine. Flame retardant activity of the epoxy resin filled with Silica-PAMAM-PTBBA was estimated by limiting oxygen index (LOI). The LOI of epoxy resin filled with Silica-PAMAM-PTBBA was higher than that filled with untreated silica and free PTBBA. It was confirmed that the flame retardant activity of epoxy resin was improved by the addition of the Silica-PAMAM-PTBBA. The elimination of PTBBA from the epoxy resin filled with Silica-PAMAM-PTBBA into boiling water was hardly observed by immobilization of PTBBA onto silica surface. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6145–6152, 2009