Takahiro Gunji

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Organization: Tokyo University of Science

Department: Department of Pure and Applied Chemistry, Faculty of Science and Technology

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Polymer

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References

Syntheses of cage octasilicate polymers

Co-reporter:Takahiro Gunji;Takahiro Igarashi

Journal of Sol-Gel Science and Technology 2017 Volume 81( Issue 1) pp:21-26

Publication Date(Web):2017 January

DOI:10.1007/s10971-016-3998-z

Octakistetramethylammonium octasilsesquioxane (Q8TMA) was synthesized from water glass (No. 3) by neutralization, extraction with tetrahydrofuran, and condensation reaction using tetramethylammonium hydroxide. Octakisdimethylsilyl octasilsesquioxane (Q8DMS) was synthesized by the reaction of Q8TMA with chloro(dimethyl)silane. An all-siloxane-type cage-containing polymer was synthesized by the reaction of Q8DMS with water by using diethylhydroxylamine as a catalyst. The reaction of Q8DMS with diphenylsilanediol was carried out to provide oligomers. This reaction was carried out by the addition of Q8DMS twice to isolate a cage-containing polymer with a weight-average molecular weight of 18,000.

Synthesis of poly(3-(4-ethoxysulfonylphenoxy)-2-methylpropyl)silsesquioxane and its application as a proton-conducting membrane

Co-reporter:Satoru Tsukada, Akira Tomobe, Yoshimoto Abe and Takahiro Gunji

Polymer Journal 2015 47(4) pp:287-293

Publication Date(Web):December 10, 2014

DOI:10.1038/pj.2014.112

A polysilsesquioxane-based organic-inorganic hybrid membrane was prepared and applied as a proton-conducting membrane for fuel cells. poly(STES-ran-MTES), a random copolymer of ethyl 4-(2-methyl-3-triethoxysilylpropoxy)benzenesulfonate (STES) and triethoxy(methyl)silane (MTES) was synthesized by hydrolysis and condensation in the presence of hydrochloric acid under a nitrogen stream. The molecular weight was 7500–7600 g mol−1, and the percentage of hydrolyzed ethoxysulfonyl group was 32–50%. A poly(STES-ran-MTES) membrane was prepared by heating for several days, which showed thermal resistivity up to 200 °C and proton conductivity of 2.0 × 10−5 to 1.1 × 10−3 S cm−1 at room temperature. By contrast, a membrane of a block copolymer, poly(SPES-block-PMS), showed proton conductivity of 2.5 × 10−3 S cm−1. The proton conductivity of the poly(3-(4-ethoxysulfonylphenoxy)-2-methylpropyl)silsesquioxane (SPES) membrane increased from 2.7 × 10−3 S cm−1 at 25 °C to 1.0x10−2 S cm−1 at 110 °C. The proton conductivity of the SPES membrane increased from 2.7 × 10−3 S cm−1 at relative humidity (RH)=25–30% to 2.0 × 10−3 S cm−1 at RH=60% and 1.4 × 10−1 S cm−1 at RH=90%. The mixture of SPES and poly(vinyl alcohol), poly(ethylene oxide) or polyoctahedralpolysilsesquioxane showed proton conductivities of 2.7 × 10−3, 1.5 × 10−3 and 2.5 × 10−3 S cm−1, respectively, at 25 °C and RH=25–30%. The open-circuit voltage of the SPES membrane was 0.92 V.

Preparation, properties, and structure of polysiloxanes by acid-catalyzed controlled hydrolytic co-polycondensation of polymethyl(methoxy)siloxane and polymethoxysiloxane

Co-reporter:Takahiro Gunji;Hironori Kaburagi

Journal of Sol-Gel Science and Technology 2015 Volume 75( Issue 3) pp:564-573

Publication Date(Web):2015 September

DOI:10.1007/s10971-015-3727-z

Polysiloxanes were prepared by acid-catalyzed controlled hydrolytic co-polycondensation of polymethyl(methoxy)siloxanes (PMS) and polymethoxysiloxanes (PMOS) obtained as macromonomers by acid-catalyzed controlled hydrolytic polycondensation of methyl(trimethoxy)silane and tetramethoxysilane, respectively. Co-polycondensation of the macromonomers with molecular weights Mw 2000 (PMS) and 400 (PMOS) provided polymethylsiloxane copolymers with molecular weights Mw 6500–15,000. The structure was confirmed to consist of block copolymers poly(PMS-block-PMOS) based on the results of gel permeation chromatography, isolation by fractional precipitation with THF and hexane, and 1H and 29Si NMR spectral analyses. The copolymers were soluble in organic solvents, except for hexane, and were fairly stable to self-condensation even without an end block. Transparent and flexible free-standing films were obtained from a 20 wt% THF solution of polymers. The surface morphology of films by FE-SEM and IR microscopic spectral analyses revealed cross-shaped crystalline materials on the film surface of poly(PMS-block-PMOS); these materials consisted of silsesquioxane unit structures depending on the compositions of PMS and PMOS.

Unexpected Formation of 2-Amino-(1-(2-nitrophenylsulfinyl)azulene by the Reaction of 2-Aminoazulene with 2-Nitrobenzenesulfonyl Chloride

Co-reporter:Hajime Nakagawa;Satoru Tsukada;Noritaka Abe

Heteroatom Chemistry 2014 Volume 25( Issue 5) pp:389-395

Publication Date(Web):

DOI:10.1002/hc.21173

ABSTRACT

2-Amino-(1-(2-nitrophenylsulfinyl)azulene derivatives were synthesized by the reaction of 2-aminoazulene with 2-nitrobenzenesulfonyl chloride. Crystal structures of these compounds were determined by X-ray diffraction analysis. The sulfur atom derived nosyl group shows unique geometry. Furthermore, a reaction using 4-nitrobenzenesulfonyl chloride is also demonstrated.

Preparation and properties of a fullerene/polysiloxane hybrid from chemically modified fullerene and polymethoxysiloxane

Co-reporter:Takahiro Gunji;Kengo Hirama;Satoru Tsukada

Journal of Sol-Gel Science and Technology 2014 Volume 72( Issue 1) pp:80-84

Publication Date(Web):2014 October

DOI:10.1007/s10971-014-3413-6

An organic–inorganic hybrid was prepared by simply mixing a fullerene derivative with polymethoxysiloxane. First, C60 was subjected to a radical addition reaction with 4,4′-azobis(4-cyanovaleric acid) to provide a C60 derivative. Polymethoxysiloxane was prepared by a controlled hydrolytic condensation of tetramethoxysilane. These two compounds were mixed and heated to provide hybrid bulk body. The hybrid bulk body showed high mechanical strength and elastic modulus compared with polymethoxysiloxane or the C60/polymethoxysiloxane hybrid. The formation of a dense siloxane network was established by a homogeneous mixing of the C60 derivative with polymethoxysiloxane.

Preparation of co-polymethyl(alkoxy)siloxanes by acid-catalyzed controlled hydrolytic copolycondensation of methyl(trialkoxy)silane and tetraalkoxysilane

Co-reporter:Takahiro Gunji;Takayoshi Tozune;Hironori Kaburaki;Kouji Arimitsu ;Yoshimoto Abe

Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 22) pp:4732-4741

Publication Date(Web):

DOI:10.1002/pola.26904

ABSTRACT

Polymethyl(alkoxy)siloxane copolymers, poly(MTES-co-TEOS), and poly(MTMS-co-TMOS), are prepared by acid-catalyzed controlled hydrolytic co-polycondensation of methyl(trialkoxy)silane MeSi(OR)₃ (R = Et (MTES) and Me (MTMS)) and tetra-alkoxysilane Si(OR)₄ (R = Et (TEOS) and Me (TMOS)), respectively. The products are purified by fractional precipitation to provide polymethyl(alkoxy)siloxane copolymers with molecular weight 1000–10,000 (poly(MTES-co-TEOS)) or 1700–100,000 (poly(MTMS-co-TMOS)) that are stable to self-condensation. These polymers are soluble in common organic solvents except for hexane, and form flexible and transparent free-standing films with a tensile strength of 4.0–10.0 MPa. The structure of the polymethyl(alkoxy)siloxane copolymers is thought to be a random or a block co-polymer. They are found to provide coating films with an adhesive strength up to 10, a refractive index of 1.36–1.40, and a dielectric constant of 3.5–3.6. The products also show better weathering stability than polyethoxysiloxane due to the hydrolytic polycondensation of TEOS. Field emission-scanning electron micrography analysis reveals that coating films are composed of a micro-phase separated structure. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4732–4741

Preparation of platinum nanoparticles that are dispersible in water over a wide pH range

Co-reporter:Takanori Imai;Yoshimoto Abe;Keishi Nishio;Ryuji Tamura;Hirobumi Shibata;Tohru Kineri;Takahiro Gunji

Polymer Journal 2013 45(5) pp:540-544

Publication Date(Web):2012-09-19

DOI:10.1038/pj.2012.173

Platinum nanoparticles stabilized by linear polyethyleneimine (LPEI) were prepared by the liquid-phase reduction of chloroplatinic(IV) acid with sodium borohydride. The average radii of particles were 3.26 and 1.76 nm when the molecular weights of LPEI were 25 000 and 2150, respectively. These nanoparticles were well dispersed in water in the pH range of 1–6. Branched polyethyleneimine also provided nanoparticles that dispersed in water in the pH range of 0–8. Linear poly(ethyleneimine-co-N-methylethyleneimine) gave nanoparticles that dispersed in water in the pH range of −1 to 15. The dispersibility of the nanoparticles decreased with increasing content of the N-methyl group.

Preparation of polymer-protected NiMoPt alloy nanoparticles dispersible in water over a wide pH range by a hot-soap method and ligand-exchange reaction

Co-reporter:Takanori Imai;Yoshimoto Abe;Keishi Nishio;Ryuji Tamura;Hirobumi Shibata;Tohru Kineri;Satoru Tsukada;Takahiro Gunji

Polymer Journal 2013 45(9) pp:993-996

Publication Date(Web):2013-02-27

DOI:10.1038/pj.2013.9

The reduction of bis(acetylacetonato)platinum(II), nickel(II) acetate tetrahydrate and molybdenum(II) acetate dimer in a mixed solvent of oleylamine and diphenyl ether using 1,2-hexadecanediol resulted in the production of oleylamine-protected ternary alloy nanoparticles (nickel–molybdenum–platinum ternary alloy nanoparticles (NiMoPtNPs)). A ligand-exchange reaction with 50% N-methylated linear poly(ethyleneimine-co-N-methylethyleneimine) (poly(EI-co-NMEI)) in chloroform yielded poly(EI-co-NMEI)-protected NiMoPtNPs. The resultant nanoparticles had average diameters of 1.9–2.5 nm and could be dispersed in water at pH levels ranging from −1 to 14. The average radii of the NiMoPtNPs decreased when the protecting polymer was changed from oleylamine to poly(EI-co-NMEI). Energy-dispersive X-ray spectroscopy of the poly(EI-co-NMEI)-protected NiMoPtNPs was performed to confirm the formation of polymer-protected alloy nanoparticles of nickel, molybdenum and platinum.

Preparation and properties of flexible free-standing films via polyalkoxysiloxanes by acid-catalyzed controlled hydrolytic polycondensation of tetraethoxysilane and tetramethoxysilane

Co-reporter:Takahiro Gunji;Yuki Hayashi;Akemi Komatsubara;Koji Arimitsu;Yoshimoto Abe

Applied Organometallic Chemistry 2012 Volume 26( Issue 1) pp:32-36

Publication Date(Web):

DOI:10.1002/aoc.1861

Acid-catalyzed controlled hydrolytic polycondensation of tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS) provided polyalkoxysiloxanes PEOS and PMOS, with high molecular weight of 1100–12 000 or 2700–31 000, respectively. They were stable to self-condensation, soluble in organic solvents, and especially characterized by high silica content of up to 62% (PEOS) and 72% (PMOS). Flexible and transparent free-standing films with tensile strength of 1.6–5.2 MPa (PEOS) or 3.6–11.8 MPa (PMOS) were prepared by heating polyalkoxysilanes at 80°C for one to several days. They are also regarded to be a potential precursor for coatings and binders. Copyright © 2012 John Wiley & Sons, Ltd.

Preparation and properties of polyhedral oligomeric silsesquioxane polymers

Co-reporter:Takahiro Shioda;Noritaka Abe;Yoshimoto Abe

Applied Organometallic Chemistry 2011 Volume 25( Issue 9) pp:661-664

Publication Date(Web):

DOI:10.1002/aoc.1820

Abstract

Polyhedral oligomeric silsesquioxane (POSS) polymers were synthesized by the dehydrogenative condensation of (HSiO_3/2)₈ with water in the presence of diethylhydroxylamine followed by trimethylsilylation. Coating films were prepared by spin-coating of the coating solution prepared by the dehydrogenative condensation of POSS. The hardness of the coating films was evaluated using a pencil-hardness test and was found to increase up to 8H with increases in the curing temperature. Free-standing film and silica gel powder were prepared by aging the coating solution at room temperature. The silica gel powder was subjected to heat treatment under air atmosphere to show a specific surface area of 440 m² g⁻¹ at 100 °C, which showed a maximum at 400 °C as 550 m² g⁻¹. Copyright © 2011 John Wiley & Sons, Ltd.

Stereochemistry of the reaction of cis,trans,cis-2,4,6,8-tetraisocyanato-2,4,6,8-tetramethylcyclotetrasiloxane with triphenylsilanol and 1,1,3,3-tetraphenyldisiloxane-1,3-diol

Co-reporter:Hiroyasu Seki, Yoshimoto Abe, Takahiro Gunji

Journal of Organometallic Chemistry 2011 696(4) pp: 846-851

Publication Date(Web):

DOI:10.1016/j.jorganchem.2010.10.013

Preparation of free-standing films with sulfonyl group from 3-mercaptopropyl(trimethoxy)silane1,2-bis(triethoxysilyl)ethane copolymer

Co-reporter:Takahiro Gunji, Yasunobu Shigematsu, Takashi Kajiwara and Yoshimoto Abe

Polymer Journal 2010 42(8) pp:684-688

Publication Date(Web):June 23, 2010

DOI:10.1038/pj.2010.52

3-Mercaptopropyl(trimethoxy)silane (MTMS)/1,2-bis(triethoxysilyl)ethane copolymer was synthesized by the hydrolytic polycondensation of the two alkoxysilanes in the presence of hydrochloric acid as a catalyst under nitrogen flow. Free-standing films were prepared by heating the copolymer at 80 °C for 4 days. The films were dipped in a 30% hydrogen peroxide solution at room temperature for 4 days. The sulfonated films were stable against hydrolysis and maintained their form at 150 °C. The sulfonyl group content of the film at 150 °C was 1.20 mmol g−1 when the composition of MTMS/1,2-bis(trimethoxysilyl)ethane was 1:2.

Preparation and properties of polyhedral oligomeric silsesquioxanepolysiloxane copolymers

Co-reporter:Takahiro Gunji;Takahiro Shioda;Koji Tsuchihira;Hiroyasu Seki;Takashi Kajiwara;Yoshimoto Abe

Applied Organometallic Chemistry 2010 Volume 24( Issue 8) pp:545-550

Publication Date(Web):

DOI:10.1002/aoc.1562

Abstract

All siloxane-type siloxane–polyhedral oligomeric silsesquioxane [(HSiO_3/2)₈, T₈^H] copolymers were synthesized by the dehydrogenative condensation of T₈^H with diphenylsilanediol, tetraphenyldisiloxane-1,3-diol or silanol-terminated polydimethylsiloxanes in the presence of diethylhydroxylamine followed by trimethylsilylation. Coating films were prepared by spin-coating of the coating solutions prepared from the dehydrogenative condensation products. The hardness of the coating films was evaluated by a pencil hardness test and was found to increase up to 6H with increases in the curing temperature. Silica gels were prepared by concentrating the coating solution following by pyrolysis. These silica gels showed a specific surface area 449 m²/g at 650 °C corresponding to the formation of a silica network in response to combustion of the phenyl groups. Copyright © 2009 John Wiley & Sons, Ltd.

Synthesis and structure of ladder polymethylsilsesquioxanes from sila-functionalized cyclotetrasiloxanes

Co-reporter:Hiroyasu Seki, Takashi Kajiwara, Yoshimoto Abe, Takahiro Gunji

Journal of Organometallic Chemistry 2010 695(9) pp: 1363-1369

Publication Date(Web):

DOI:10.1016/j.jorganchem.2010.02.008

Syntheses of linear ethoxysiloxanes by the oxidative condensation of triethoxysilane

Co-reporter:Naoto Ueda;Yoshimoto Abe

Journal of Sol-Gel Science and Technology 2008 Volume 48( Issue 1-2) pp:

Publication Date(Web):2008 November

DOI:10.1007/s10971-008-1808-y

Linear ethoxysiloxanes were synthesized by the oxidative condensation of hydrosilane. Triethoxysilane was subjected to oxidation to form triethoxysilanol, and pentaethoxydisiloxane was formed by the condensation reaction of triethoxysilane with triethoxysilanol. Pentaethoxydisiloxane was also subjected to oxidative condensation to form a mixture of nona- and decaethoxytetrasiloxanes. In contrast, pentaethoxydisiloxane, heptaethoxytrisiloxane, and nonaethoxytetrasiloxanes were subjected to the reaction with ethanol in the presence of zinc to isolate hexaethoxydisiloxane, octaethoxytrisiloxane, and decaethoxytetrasiloxane, respectively.

Preparation and characterization of mesoporous silica thin films from polyethoxysiloxanes

Co-reporter:Takahiro Gunji;Ryosuke Shimano;Koji Arimitsu;Yoshimoto Abe

Journal of Polymer Science Part A: Polymer Chemistry 2006 Volume 44(Issue 8) pp:2542-2550

Publication Date(Web):3 MAR 2006

DOI:10.1002/pola.21344

Tetraethoxysilane (TEOS) and polyethoxysiloxanes (PEOSs; prepared by the acid-catalyzed hydrolytic polycondensation of TEOS) were subjected to the sol–gel process in the presence of cetyltrimethylammonium bromide (CTAB), respectively. The PEOSs with M_w 700–26,000, as prepared by sol–gel coating of TEOS and PEOS under various conditions, were used. Uniform and crack-free thin films of thickness 276–613 nm were prepared by spin-coating of a PEOS solution containing CTAB. When the coating films were sintered at 400 °C, the combustion of ethoxy groups and CTAB took place to provide porous silica thin films. The structure of the thin films was found to be dependent on the molecular weight of PEOS and the molar ratio of CTAB/Si: lamellar or hexagonal phase was observed for M_w less than 15,000 and for CTAB/Si molar ratios greater than 0.10. Honeycomb structures were observed for M_w less than 5000 and for CTAB/Si molar ratios of 0.15. The honeycomb structure was also observed by atomic force microscopy and transmission electron microscope. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2542–2550, 2006

Preparation of polymethylsilsesquioxanes by the base-catalyzed hydrolytic polycondensation of triisopropoxy(methyl)silane

Co-reporter:Takahiro Gunji;Satoshi Tanikawa;Koji Arimitsu;Yoshimoto Abe

Journal of Polymer Science Part A: Polymer Chemistry 2005 Volume 43(Issue 16) pp:3623-3630

Publication Date(Web):5 JUL 2005

DOI:10.1002/pola.20838

Base-catalyzed hydrolytic polycondensation of trialkoxymethylsilane was investigated to synthesize polymethylsilsesquioxanes (PMSs). The reaction of trimethoxy(methyl)silane and triethoxy(methyl)silane with tetramethylammonium hydroxide, tetrabutylammonium hydroxide, and also coline gave insoluble gels. Polymethylsilsesquioxane (PMS-IP) was obtained by the reaction of triisopropoxy(methyl)silane (MTIPS) with tetrabutylammonium hydroxide as a catalyst. PMS-IP was composed primarily of T² and T³ units. The percentage of T³ units and the molecular weight of PMS-IP increased with increases in the molar ratios of catalyst and water to MTIPS and with the reaction time. PMS-IP was soluble in organic solvents, except for methanol, and was separated by extraction with hexane and methanol into low- and high-molecular-weight fractions of M_w 2800–4000 and 7300–88,300, respectively. PMS-IP coating films were prepared by dip coating on the organic, inorganic, and metal substrates, using the acetone–isopropyl alcohol solution of PMS-IP. Since PMS-IP solutions prepared with tetrabutylammonium hydroxide were hardly used because of the low content of hydroxy groups in the polymer, they showed low adhesion when compared with those solutions prepared with hydrochloric acid. The dielectric constant of the coating film prepared from the high-molecular-weight PMS-IP was 2.6. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3623–3630, 2005

Synthesis, isolation, and characterization of polytitanasiloxanes and zirconasiloxanes by the hydrolytic cocondensation of tetraethoxysilane and titanium or zirconium tetraisopropoxide

Co-reporter:Masahiro Hongo;Masanari Yokogawa;Yoshimoto Abe

Journal of Polymer Science Part A: Polymer Chemistry 2005 Volume 43(Issue 4) pp:763-772

Publication Date(Web):5 JAN 2005

DOI:10.1002/pola.20546

Polytitanasiloxanes and polyzirconasiloxanes were synthesized through the hydrolytic cocondensation of tetraethoxysilane (TEOS) and tetraisopropoxytitanium (TPT) or tetraisopropoxyzirconium (TPZ) 2-propanol adduct (process A) and through the reaction of partially hydrolyzed TEOS with TPT or TPZ (process B) and were isolated as acetylacetonato derivatives stable against self-condensation. In both processes, acetylacetone was added to provide acetylacetonato derivatives of polytitanasiloxanes and polyzirconasiloxanes. In process A, titanium- or zirconium-rich polymetallasiloxanes were formed during the initial stage of the process, whereas the molar ratio of silicon to titanium or zirconium was gradually increased up to almost unity with an increasing reaction time. In process B, the molar ratio gradually increased below and above unity as the molar ratio of water to TEOS increased. When the acetylacetonato derivatives of polymetallasiloxanes were subjected to heat treatment, the titania or zirconia component was crystallized. The crystallization temperature increased as the silica content and the molar ratio of water to TEOS increased, and this demonstrated that the crystallization was dependent on the sequence in the main chain of the polymetallasiloxanes. The ²⁹Si NMR spectra of the polymetallasiloxanes led to the idea that the backbone metallasiloxane linkages consisted of random and block sequences for processes A and B, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 763–772, 2005