Co-reporter:Yoko Matsuzawa, Yuko Takada, Hirokuni Jintoku, Hideyuki Kihara, and Masaru Yoshida
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 42) pp:28400
Publication Date(Web):October 10, 2016
DOI:10.1021/acsami.6b06169
We describe the application of photodetachable and recyclable dispersants for single-walled carbon nanotubes (SWNTs) in the fabrication of photopatterned SWNT thin films. Because adsorption and desorption of the dispersants on the SWNT surfaces affect not only their dispersibility in water but also their solubility, SWNT photopatterns were obtained on glass substrates in only three steps, i.e., casting the SWNT/dispersant solution, UV-light exposure of the casted SWNT/dispersant films through a photomask, and subsequent rinsing with neutral water. This patterning procedure is simple and scalable and will enable us to prepare microfabricated SWNT thin films.Keywords: adsorption/desorption; carbon nanotubes; patterned thin films; photoisomerization; surfaces
Co-reporter:Jun'ichi Nagasawa;Sonoko Wakahara;Hajime Matsumoto;Hideyuki Kihara
Journal of Polymer Science Part A: Polymer Chemistry 2015 Volume 53( Issue 2) pp:249-255
Publication Date(Web):
DOI:10.1002/pola.27310
ABSTRACT
Polymer electrolytes containing N,N′-(trans-cyclohexane-1,4-diyl)dibenzamide linkages, polyethylene ((CH2)m, m = 2, 4, 10) spacers, and bis(trifluoromethanesulfonyl)amide (TFSA) or bis(fluorosulfonyl)amide (FSA) counteranions (polymer abbreviation: CDBAm•X; m = 2, 4, 10; X = TFSA, FSA) have been synthesized, adding to our previous report (m = 6). In addition, their ability to effect the gelation of six ionic liquids and the properties of the resulting ionogels have been examined. The polymers, except for CDBA10•TFSA, effect the gelation for all ionic liquids used in this study at fairly low concentrations (0.9–50 g/L). Ionogel ionic conductivity is not dependent on the spacer length, but does decrease slightly as increasing amounts of the gelatinizer are introduced. In contrast to ionic conductivity, the temperatures at which these ionogels transition into isotropic fluids is dependent on the spacer length; the gel composed of [EMI][FSA] and 100 g/L of CDBA6•FSA transforms at 120 °C, while the gel composed of [EMI][FSA] and 5 g/L of CDBA2•FSA does not transform into a sol even when temperatures become 155 °C. In brief, ionogel heat resistance can be improved by changing the spacer length of the polyelectrolyte. Finally, it has been determined using cyclic voltammetry that the potential window of the polyelectrolytes is particularly wide, ranging from −1.6 to 2.5 V. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 249–255
Co-reporter:Yoko Matsuzawa ; Yuko Takada ; Tetsuya Kodaira ; Hideyuki Kihara ; Hiromichi Kataura
The Journal of Physical Chemistry C 2014 Volume 118(Issue 9) pp:5013-5019
Publication Date(Web):February 14, 2014
DOI:10.1021/jp411964z
A purification method for raw single-walled carbon nanotubes (SWCNTs) without damage to their intrinsic structures has been desired in many applications. We investigated the purification of SWCNTs based on high-speed centrifugation of water-dispersed SWCNTs using the photoreactive dispersant we previously investigated. SWCNTs wrapped with the dispersant were separated from impurities, such as an amorphous carbon and metal particles by centrifugation, similarly to conventional physical purification using surfactants. In contrast to general surfactants that form micelles to disperse SWCNTs in aqueous solutions, the photoreactive dispersant did not form micelles. Therefore, an excess amount of the dispersant, which did not adsorb onto the SWCNT surfaces, was removable by dialysis of the supernatant. Since the amount of the dispersant was minimized by dialysis, we tuned the UV-irradiation time to eliminate the dispersibility of SWCNTs in water to as low a value as ∼2 h. The SWCNT precipitates were collected, and their chemical and structural purity were evaluated using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and resonance Raman spectroscopy. It was found that present methods combining high-speed centrifugation and photoreactive dispersant provided an effective procedure to purify SWCNTs without any apparent changes to their intrinsic properties.
Co-reporter:Hideyuki Kihara and Masaru Yoshida
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 7) pp:2650
Publication Date(Web):March 7, 2013
DOI:10.1021/am400111q
As new organic materials for rewritable photopatterning, 2-anthroyl and 9-anthroyl ester compounds were synthesized. Their bulk-phase changes (we use “bulk-phase change” as complete phase change in a mass of a material neither in a surface nor in a small quantity in this study) triggered by photodimerization under melting conditions (melt-photodimerization) and subsequent thermal back reactions were investigated. All the anthroyl compounds exhibited melting points lower than ca. 160 °C, and they were nearly quantitatively converted to the corresponding photodimers by UV irradiation at temperatures of ∼5 °C higher than their respective melting points. We found that there were two kinds of bulk-phase change behaviors through the photoreaction. Two of the anthroyl compounds remained isotropic and lost fluidity during the melt-photodimerization. The obtained photodimers exhibited robust solid-state amorphous phases at room temperature. In contrast, the other three anthroyl compounds showed crystallization during the melt-photodimerization. The resulting photodimers changed from isotropic to crystalline phases, even at high temperature. Various experiments revealed that the bulk phase of the photodimers was affected not by the existence of regioisomers but by their fluidity at the photoirradiation temperature. The latter three photodimers retained enough fluidity, reflecting their high molecular mobilities at the photoirradiation temperature at which the isothermal crystallization occurred. The other two products were not able to crystallize due to low fluidity, resulting in amorphous phases. We also found that all the photodimers reverted to the corresponding monomers by thermal back reaction and recovered their initial photochemical and thermal properties. Using these reversible bulk-phase changes of the anthroyl compounds, we successfully demonstrated rewritable photopatterning in not only negative images but also positive ones, based on the optical contrast between the ordered and disordered phases.Keywords: anthracene; dimerization; phase transition; photochemistry; photopatterning;
Co-reporter:Yoshiko Takenaka, Youhei Kawabata, Hiroyuki Kitahata, Masaru Yoshida, Yoko Matsuzawa, Takuya Ohzono
Journal of Colloid and Interface Science 2013 Volume 407() pp:265-272
Publication Date(Web):1 October 2013
DOI:10.1016/j.jcis.2013.06.008
•Gold nanorods (aspect ratio >20) were synthesized with a modified seeding method.•Longer nanorods grow at higher surfactant concentrations.•Surfactant self-assemblies were analyzed using small-angle X-ray scattering.•Complex formation of gold ions with HTAB micelles suppresses secondary nucleation.•Suppressing secondary nucleation is important to elongate gold nanorods.The effects of surfactant concentration in a growth solution on the elongation of gold nanorods were examined. Gold nanorods were synthesized in solutions with different concentrations of hexadecyltrimethylammonium bromide (HTAB): 100, 200, 300, 400, 500, and 600 mM. The nanorods grown in a solution with higher surfactant concentrations were longer (aspect ratio ∼30) than those grown in that with lower concentrations (aspect ratio <10). The self-assembled surfactant structures in the solutions were analyzed using viscosity measurement and small-angle X-ray scattering. These results showed a decrease in the inter-micellar distance with increasing surfactant concentration. Taking the chemical equilibrium for the complex formation between Au ions and HTAB micelles into account, we found that the free Au ion concentration decreases accompanied with the increase in the surfactant concentration. This decrease in the free Au ion concentration suppresses undesirable secondary nucleation of gold crystals in a growth solution, resulting in gold nanorod elongation.Graphical abstract
Co-reporter:Jun’ichi Nagasawa, Hajime Matsumoto, and Masaru Yoshida
ACS Macro Letters 2012 Volume 1(Issue 9) pp:1108
Publication Date(Web):August 21, 2012
DOI:10.1021/mz3002808
We synthesized gel-forming polyelectrolytes having N,N′-(trans-cyclohexane-1,4-diyl)dibenzamide linkages, with chloride, bis(trifluoromethanesulfonyl)amide, bis(fluorosulfonyl)amide, or tetrafluoroborate anions that could gelatinize a variety of ionic liquids at very low concentrations. The temperatures at which these ionogels transitioned into isotropic fluids were greater than 100 °C even at concentrations as low as 5 g/L. In addition, the ionogels exhibited high mechanical strength without a significant loss in their ionic conductivities, along with the rapid recovery.
Co-reporter:Hideyuki Kihara, Yasuo Norikane, Masaru Yoshida
Tetrahedron 2012 68(27–28) pp: 5513-5521
Publication Date(Web):
DOI:10.1016/j.tet.2012.04.083
Co-reporter:Takahiro Yamamoto and Masaru Yoshida
Langmuir 2012 Volume 28(Issue 22) pp:8463-8469
Publication Date(Web):May 23, 2012
DOI:10.1021/la3001784
We investigated viscoelastic and photoresponsive properties of the microparticle/liquid-crystal (LC) composite gels. The mechanical strength of the colloidal gels can be widely tuned by varying particle concentrations. With increasing particle concentration, a storage modulus of the particle/LC composite gels increased and reached over 104 Pa, showing good self-supporting ability. We demonstrated for the first time that the particle/LC composite gels exhibited rapid and repetitive recovery of the mechanical strength after large-amplitude oscillatory breakdown. In addition, photoresponsive properties of the composite gels were investigated by the cis–trans photoisomerization of the azobenzene compound doped into the host LCs. The photochemical gel–sol transition could be repeatedly induced by changing the phase structure of the host LCs between nematic and isotropic, using the photoisomerization. The particle/LC composite gels can be applied to optically healable materials by the site-selective gel–sol transition based on the photochemical modulation of the phase structures of the host LCs.
Co-reporter:Nagatoshi Koumura, Hajime Matsumoto, Hajime Kawanami, Nobuyuki Tamaoki and Masaru Yoshida
Polymer Journal 2010 42(9) pp:759-765
Publication Date(Web):August 4, 2010
DOI:10.1038/pj.2010.65
To tune the miscibility of the gel-forming oligomeric electrolyte, we examined anion exchange reactions using appropriate ammonium or alkali-metal salts. Nine oligomeric electrolytes with different anions were obtained in high yields by the reactions. The solubility of these oligomeric electrolytes in organic solvents was carefully tested. Although the starting material with chloride as a counter anion was not soluble in any organic solvents, excellent miscibility and gelation ability of the oligomeric electrolytes with different anions were consequently observed with dipolar protophilic and aprotic solvents such as N,N-dimethylformamide, dimethylsulfoxide and N,N-dimethylacetamide. Furthermore, ionogels based on aliphatic ionic liquids were readily formed using the oligomer with bis(trifluoromethanesulfonyl)amide anion at a 40 g l−1 concentration. It is remarkable that the ionic conductivity of the above-mentioned ionogels is almost identical to that of neat ionic liquids, despite the significant increase in the apparent viscosity. This study shows a novel and convenient approach to gelators for multiple solvents.
Co-reporter:Masaru Yoshida
The Chemical Record 2010 Volume 10( Issue 4) pp:230-242
Publication Date(Web):
DOI:10.1002/tcr.201000007
Abstract
In this article, novel gel-forming materials based on oligomeric and polymeric electrolytes for not only water but also organic solvents, including ionic liquids, are highlighted especially the synthesis, derivatization, and physical property. The oligoelectrolytes with cationic pyridinium backbone can be very easily prepared by the intermolecular quaternization of the ampholytic monomer. The ionene polymers with N,N′-(p-phenylene)dibenzamide linkages as polyelectrolyte were also straightforwardly synthesized in high yields by the copolymerization of 1,4-bis[4-(chloromethyl)benzamide]benzene and commercially available α,ω-ditertiary amines. The oligo- and polyelectrolytes provided physical hydrogels under ca. 1–5 wt% of the concentrations after heating and cooling at room temperature without any other additives. These cationic gelators have characteristic properties, such as acid resistance, a self-healing nature after mechanical collapse, and a dispersant ability for single-walled carbon nanotubes, which have been rarely attainable for conventional physical gelators. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 10: 230–242; 2010: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.201000007
Co-reporter:Yoshihiro Misawa, Nagatoshi Koumura, Hajime Matsumoto, Nobuyuki Tamaoki and Masaru Yoshida
Macromolecules 2008 Volume 41(Issue 22) pp:8841-8846
Publication Date(Web):October 24, 2008
DOI:10.1021/ma801350k
Ionene polymers with N,N′-(p-phenylene)dibenzamide linkages were synthesized in high yields by the copolymerization of 1,4-bis[4-(chloromethyl)benzamide]benzene and α,ω-ditertiary amines in N,N-dimethylformamide. The ionene polymers provided physical hydrogels under ca. 1−5 wt % of the concentrations after heating and cooling at room temperature without any other additives. The gelation ability was dependent on the diamine spacers and/or the molecular weights, and the ionene polymer with the longest hexylene linker connecting ammonium cations was the most effective gelation capability in water among these ionene polymers. In the rheological measurement, the hydrogel showed a unique thixotropic nature that was a fast self-recovering property after the continuous oscillatory shear stress. Furthermore, the ionene polymer has an additional function as a dispersant for single-walled carbon nanotubes (SWNT) in water.
Co-reporter:Masaru Yoshida, Seiji Tsuzuki and Nobuyuki Tamaoki
Organic & Biomolecular Chemistry 2001 (Issue 7) pp:1021-1023
Publication Date(Web):05 Jun 2001
DOI:10.1039/B102759J
In contrast to the proposed structures of 1 ∶ 1 complexes of the chair-form pyxophane1 with Na+ and `external' 2 ∶ 1 complexes with K+, DFT calculations suggest that 1 prefers the saddle-form in the complexes due to the induced-fit conformational change and that 1 forms an `internal' 2 ∶ 1 complex with K+.