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Koga M, Matsumoto H, Kunishima M, Tokita M, Masunaga H, Ohta N, Takeuchi A, Mizukado J, Sugimori H, Shinohara K, Uemura S, Yoshida T, Hirai S. Microstructure Investigation of Polymer Electrolyte Fuel Cell Catalyst Layers Containing Perfluorosulfonated Ionomer. Membranes (Basel) 2021; 11:466. [PMID: 34202780 DOI: 10.3390/membranes11070466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 06/16/2021] [Accepted: 06/22/2021] [Indexed: 11/17/2022]
Abstract
Perfluorosulfonated ionomers are the most successful ion-exchange membranes at an industrial scale. One recent, cutting-edge application of perfluorosulfonated ionomers is in polymer electrolyte fuel cells (PEFCs). In PEFCs, the ionomers are used as a component of the catalyst layer (CL) in addition to functioning as a proton-exchange membrane. In this study, the microstructures in the CLs of PEFCs were characterized by combined synchrotron X-ray scattering and transmission electron microscopy (TEM) analyses. The CL comprised a catalyst, a support, and an ionomer. Fractal dimensional analysis of the combined ultrasmall- and small-angle X-ray scattering profiles indicated that the carbon-black-supported Pt catalyst (Pt/CB) surface was covered with the ionomer in the CL. Anomalous X-ray scattering revealed that the Pt catalyst nanoparticles on the carbon surfaces were aggregated in the CLs. These findings are consistent with the ionomer/catalyst microstructures and ionomer coverage on the Pt/CB surface obtained from TEM observations.
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Okugawa A, Sakaino M, Yuguchi Y, Yamane C. Relaxation phenomenon and swelling behavior of regenerated cellulose fibers affected by water. Carbohydr Polym 2019; 231:115663. [PMID: 31888833 DOI: 10.1016/j.carbpol.2019.115663] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 11/21/2019] [Accepted: 11/22/2019] [Indexed: 11/20/2022]
Abstract
Regenerated cellulose fibers are extremely sensitive to water; particularly, the mechanical properties are greatly affected by water. We examined the effect of water on regenerated cellulose fibers in respect of the relaxation phenomenon and swelling behavior. The peaks and shoulder of mechanical loss tangent δ were observed at room temperature and water regains of 56-78%. At the same time, the storage modulus markedly decreased around these water regains. Small angle X-ray scattering showed the maxima and shoulders in the wet state, which suggested that water decreased the density of the amorphous region and made space for the movement of polymer segments. It is possible that the glass transition temperatures of 510-550 K shift to room temperature at specific water regains. It is reasonable to suppose that water can penetrate into the amorphous region, loosening the interactions between cellulose molecules and widening the region, and in consequence decreasing the glass transition temperature.
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Affiliation(s)
- Akari Okugawa
- Graduate school of Kobe Women's University, 2-1 Aoyama Higashisuma, Suma-ku, Kobe, Hyogo 654-8585, Japan
| | - Manami Sakaino
- Graduate school of Kobe Women's University, 2-1 Aoyama Higashisuma, Suma-ku, Kobe, Hyogo 654-8585, Japan
| | - Yoshiaki Yuguchi
- Faculty of Engineering, Osaka Electro-Communication University, 18-8 Hatsu-cho, Neyagawa, Osaka 572-8530, Japan
| | - Chihiro Yamane
- Graduate school of Kobe Women's University, 2-1 Aoyama Higashisuma, Suma-ku, Kobe, Hyogo 654-8585, Japan.
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Wu S, Li M, Sun Y. In Situ Synchrotron X-ray Characterization Shining Light on the Nucleation and Growth Kinetics of Colloidal Nanoparticles. Angew Chem Int Ed Engl 2019; 58:8987-8995. [PMID: 30830994 DOI: 10.1002/anie.201900690] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Indexed: 11/08/2022]
Abstract
Rational synthesis of colloidal nanoparticles with desirable properties relies on precise control over the nucleation and growth kinetics, which is still not well understood. The recent development of in situ high energy synchrotron X-ray techniques offers an excellent opportunity to quantitatively monitor the growth trajectories of colloidal nanoparticles in real time under real reaction conditions. The time-resolved, quantitative data of the growing colloidal nanoparticles are unique to reveal the mechanism of nanoparticle formation and determine the corresponding intrinsic kinetic parameters. This review discusses the kinetics of major steps of forming colloidal nanoparticles and the capability of in situ synchrotron X-ray techniques in studying the corresponding kinetics.
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Affiliation(s)
- Siyu Wu
- Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, PA, 19122, USA
| | - Mingrui Li
- Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, PA, 19122, USA
| | - Yugang Sun
- Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, PA, 19122, USA
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Ree BJ, Satoh T, Yamamoto T. Micelle Structure Details and Stabilities of Cyclic Block Copolymer Amphiphile and Its Linear Analogues. Polymers (Basel) 2019; 11:E163. [PMID: 30960147 PMCID: PMC6401893 DOI: 10.3390/polym11010163] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 01/08/2019] [Accepted: 01/14/2019] [Indexed: 11/16/2022] Open
Abstract
In this study, we investigate structures and stabilities of the micelles of a cyclic amphiphile (c-PBA-b-PEO) composed of poly(n-butyl acrylate) (PBA) and poly(ethylene oxide) (PEO) blocks and its linear diblock and triblock analogues (l-PBA-b-PEO and l-PBA-b-PEO-b-PBA) by using synchrotron X-ray scattering and quantitative data analysis. The comprehensive scattering analysis gives details and insights to the micellar architecture through structural parameters. Furthermore, this analysis provides direct clues for structural stabilities in micelles, which can be used as a good guideline to design highly stable micelles. Interestingly, in water, all topological polymers are found to form ellipsoidal micelles rather than spherical micelles; more interestingly, the cyclic polymer and its linear triblock analog make oblate-ellipsoidal micelles while the linear diblock analog makes a prolate-ellipsoidal micelle. The analysis results collectively inform that the cyclic topology enables more compact micelle formation as well as provides a positive impact on the micellar structural integrity.
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Affiliation(s)
- Brian J Ree
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan.
| | - Toshifumi Satoh
- Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
| | - Takuya Yamamoto
- Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
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Ree BJ, Lee J, Satoh Y, Kwon K, Isono T, Satoh T, Ree M. A Comparative Study of Dynamic Light and X-ray Scatterings on Micelles of Topological Polymer Amphiphiles. Polymers (Basel) 2018; 10:E1347. [PMID: 30961273 PMCID: PMC6401847 DOI: 10.3390/polym10121347] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 12/03/2018] [Accepted: 12/04/2018] [Indexed: 12/15/2022] Open
Abstract
Micelles were prepared in organic solvents by using three topological polymer amphiphiles: (i) cyclic poly(n-decyl glycidyl ether-block-2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether) (c-PDGE-b-PTEGGE) and (ii) its linear analogue (l-PDGE-b-PTEGGE); (iii) linear poly(6-phosphorylcholinehexylthiopropyl glycidyl ether-block-n-dodecanoyl glycidyl ether) (l-PPCGE-b-PDDGE). For the individual micelle solutions, the size and distribution were determined by dynamic light scattering (DLS) and synchrotron X-ray scattering analyses. The synchrotron X-ray scattering analysis further found that c-PDGE-b-PTEGGE forms oblate ellipsoidal micelle in an ethanol/water mixture, l-PDGE-b-PTEGGE makes prolate ellipsoidal micelle in an ethanol/water mixture, and l-PPCGE-b-PDDGE forms cylindrical micelle in chloroform. This comparative study found that there are large differences in the size and distribution results extracted by DLS and X-ray scattering analyses. All possible factors to cause such large differences are discussed. Moreover, a better use of the DLS instrument with keeping its merits is proposed.
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Affiliation(s)
- Brian J Ree
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan.
| | - Jongchan Lee
- Department of Chemistry, Division of Advanced Materials Science, Polymer Research Institute, and Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Korea.
| | - Yusuke Satoh
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan.
| | - Kyungho Kwon
- Department of Chemistry, Division of Advanced Materials Science, Polymer Research Institute, and Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Korea.
| | - Takuya Isono
- Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
| | - Toshifumi Satoh
- Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
| | - Moonhor Ree
- Department of Chemistry, Division of Advanced Materials Science, Polymer Research Institute, and Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Korea.
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Abstract
Atomically thin MoS2/graphene heterostructures are promising candidates for nanoelectronic and optoelectronic technologies. Among different graphene substrates, epitaxial graphene (EG) on SiC provides several potential advantages for such heterostructures, including high electronic quality, tunable substrate coupling, wafer-scale processability, and crystalline ordering that can template commensurate growth. Exploiting these attributes, we demonstrate here the thickness-controlled van der Waals epitaxial growth of MoS2 on EG via chemical vapor deposition, giving rise to transfer-free synthesis of a two-dimensional heterostructure with registry between its constituent materials. The rotational commensurability observed between the MoS2 and EG is driven by the energetically favorable alignment of their respective lattices and results in nearly strain-free MoS2, as evidenced by synchrotron X-ray scattering and atomic-resolution scanning tunneling microscopy (STM). The electronic nature of the MoS2/EG heterostructure is elucidated with STM and scanning tunneling spectroscopy, which reveals bias-dependent apparent thickness, band bending, and a reduced band gap of ∼0.4 eV at the monolayer MoS2 edges.
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Affiliation(s)
- Xiaolong Liu
- Graduate Program in Applied Physics, ‡Department of Materials Science and Engineering, §Department of Physics, ∥Department of Chemistry, and ⊥Department of Medicine, Northwestern University , Evanston, Illinois 60208, United States
| | - Itamar Balla
- Graduate Program in Applied Physics, ‡Department of Materials Science and Engineering, §Department of Physics, ∥Department of Chemistry, and ⊥Department of Medicine, Northwestern University , Evanston, Illinois 60208, United States
| | - Hadallia Bergeron
- Graduate Program in Applied Physics, ‡Department of Materials Science and Engineering, §Department of Physics, ∥Department of Chemistry, and ⊥Department of Medicine, Northwestern University , Evanston, Illinois 60208, United States
| | - Gavin P Campbell
- Graduate Program in Applied Physics, ‡Department of Materials Science and Engineering, §Department of Physics, ∥Department of Chemistry, and ⊥Department of Medicine, Northwestern University , Evanston, Illinois 60208, United States
| | - Michael J Bedzyk
- Graduate Program in Applied Physics, ‡Department of Materials Science and Engineering, §Department of Physics, ∥Department of Chemistry, and ⊥Department of Medicine, Northwestern University , Evanston, Illinois 60208, United States
| | - Mark C Hersam
- Graduate Program in Applied Physics, ‡Department of Materials Science and Engineering, §Department of Physics, ∥Department of Chemistry, and ⊥Department of Medicine, Northwestern University , Evanston, Illinois 60208, United States
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