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Trevani LN, Lépori CMO, Garro Linck Y, Monti GA, Abuin GC, Vaca Chávez F, Corti HR. Speciation and Proton Conductivity of Phosphoric Acid Confined in Mesoporous Silica. ACS Appl Mater Interfaces 2022; 14:33248-33256. [PMID: 35849482 DOI: 10.1021/acsami.2c07740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Phosphoric acid (PA) confined in a commercial mesoporous silica (CARIACT G) with porous size in the range of 3 to 10 nm was studied in relation to its coordination with the silanol groups on the silica surface as a function of temperature, up to 180 °C, using 31P and 29Si MAS NMR spectroscopy. As the temperature increases, the coordination of Si and P in the mesopores depends on the pore size, that is, on the area/volume ratio of the silica matrix. In the mesoporous silica with the higher pore size (10 nm), a considerable fraction of PA is nonbonded to the silanol groups on the surface, and it seems to be responsible for its higher conductivity at temperatures above 120 °C as compared to the samples with a smaller pore size. The electrical conductivity of the functionalized mesoporous silica was higher than that reported for other silico-phosphoric composites synthesized by sol-gel methods using soft templates, which require high-temperature calcination and high-cost reagents and are close to that of the best PA-doped polybenzimidazole membranes used in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). The rate of PA release from the mesoporous silica matrix when the system is exposed to water has been measured, and it was found to be strongly dependent on the pore size. The low cost and simplicity of the PA-functionalized mesoporous silica preparation method makes this material a promising candidate to be used as an electrolyte in HT-PEMFCs.
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Affiliation(s)
- Liliana N Trevani
- Faculty of Science, Ontario Tech University, 2000 Simcoe St. North, Oshawa L1H 7K4, Ontario, Canada
| | - Cristian M O Lépori
- CONICET. Instituto de Física Enrique Gaviola (IFEG), Córdoba 5000, Argentina
| | - Yamila Garro Linck
- CONICET. Instituto de Física Enrique Gaviola (IFEG), Córdoba 5000, Argentina
- Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, Córdoba 5000, Argentina
| | - Gustavo A Monti
- CONICET. Instituto de Física Enrique Gaviola (IFEG), Córdoba 5000, Argentina
- Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, Córdoba 5000, Argentina
| | - Graciela C Abuin
- Departamento de Almacenamiento de la Energía, Instituto Nacional de Tecnología Industrial (INTI), Av. General Paz 5445, San Martín B1650KNA, Buenos Aires, Argentina
| | - Fabián Vaca Chávez
- CONICET. Instituto de Física Enrique Gaviola (IFEG), Córdoba 5000, Argentina
- Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, Córdoba 5000, Argentina
| | - Horacio R Corti
- Departamento de Física de la Materia Condensada e Instituto de Nanociencia y Nanotecnología (CNEA-CONICET), Comisión Nacional de Energía Atómica, Avda. General Paz 1499, San Martín B1650KNA, Buenos Aires, Argentina
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Ruderman A, Smrekar S, Bracamonte MV, Primo EN, Luque GL, Thomas J, Leiva E, Monti GA, Barraco DE, Vaca Chávez F. Unveiling the stability of Sn/Si/graphite composites for Li-ion storage by physical, electrochemical and computational tools. Phys Chem Chem Phys 2021; 23:3281-3289. [PMID: 33506828 DOI: 10.1039/d0cp05501h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Complex materials composed of two and three elements with high Li-ion storage capacity are investigated and tested as lithium-ion battery (LiB) negative electrodes. Namely, anodes containing tin, silicon, and graphite show very good performance because of the large gravimetric and volumetric capacity of silicon and structural support provided by tin and graphite. The performance of the composites during the first cycles was studied using ex situ magic angle spinning (MAS) 7Li Nuclear Magnetic Resonance (NMR), density functional theory (DFT) calculations, and electrochemical techniques. The best performance was obtained for Sn/Si/graphite in a 1 : 1 : 1 proportion, due to an emergent effect of the interaction between Sn and Si. The results suggest a stabilization effect of Sn over Si, providing a physical constraint that prevents Si pulverization. This mechanism ensures good cyclability over more than one hundred cycles, low capacity fading and high specific capacity.
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Affiliation(s)
- Andrés Ruderman
- Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación, Córdoba, Argentina
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Lépori CMO, Correa NM, Silber JJ, Vaca Chávez F, Falcone RD. Interfacial properties modulated by the water confinement in reverse micelles created by the ionic liquid-like surfactant bmim-AOT. Soft Matter 2019; 15:947-955. [PMID: 30644504 DOI: 10.1039/c8sm02217h] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The behavior of the interfacial water entrapped in reverse micelles (RMs) that were formed by the ionic liquid-like surfactant 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate (bmim-AOT) was investigated with the use of UV-Vis absorption spectroscopy and nuclear magnetic resonance (NMR) relaxometry. The solvatochromism of two molecular probes, namely, 1-methyl-8-oxyquinolinium betaine (QB) and N,N,N',N'-tetramethylethylenediamine copper(ii)acetylacetonate tetraphenylborate ([Cu(acac)(tmen)][B(C6H5)4]), was investigated. As a comparison, the analog RMs formed by sodium 1,4-bis-2-ethylhexylsulfosuccinate (Na-AOT) were also explored. By varying the water content inside the RMs and consequently the different magnitude of the water-surfactant interactions at the interface, interesting properties were observed by comparing bmim-AOT and Na-AOT RMs. From the solvatochromic behavior of ([Cu(acac)(tmen)][B(C6H5)4]), we found that the interface in bmim-AOT RMs shows a smaller electron donating capacity than that in Na-AOT RMs. QB revealed that the interfacial region is a weaker hydrogen bond donor and less polar than the corresponding Na-AOT RMs. NMR experiments showed that the molecular motion of water in bmim-AOT RMs is less restricted than that of the water molecules confined in Na-AOT RMs. In summary, the results show how the nature of the bmim+ cation affects the interaction between the entrapped water and the RM interface, greatly modifying the interfacial water structure in comparison with the results known for Na-AOT.
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Affiliation(s)
- Cristian M O Lépori
- Departamento de Química, Universidad Nacional de Río Cuarto, Agencia Postal # 3, C.P. X5804BYA Río Cuarto, Argentina.
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Ordikhani Seyedlar A, Martins JPDA, Sebastião PJ, Jardim Beira MJ, Stapf S, Vaca Chávez F, Mattea C. Dynamics of binary mixtures of an ionic liquid and ethanol by NMR. Magn Reson Chem 2018; 56:108-112. [PMID: 28568740 DOI: 10.1002/mrc.4620] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 05/22/2017] [Accepted: 05/26/2017] [Indexed: 06/07/2023]
Abstract
A study of molecular dynamics of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulphonyl)imide ([Emim][Tf2N]) in solution with deuterated ethanol at different molar concentration and temperatures is presented. The study was performed using 1 H and 2 H nuclear magnetic relaxation and 2 H 1D spectroscopy. The temperature dependence of the spin-lattice relaxation time T1 of the cations allows the evaluation of the activation energies of the rotational degree of freedom of these molecules. The viscosity in the binary system increases with the concentration of ionic liquid. However, the activation energy in the cation molecules decreases when the concentration of the ionic liquid increases, indicating that the rotational dynamics is facilitated. This behavior is explained from the fact that the presence of the ionic liquid in the system disrupts the degree of intermediate range order expected in the alcohol system. Copyright © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- Amin Ordikhani Seyedlar
- Department of Technical Physics II/Polymer Physics, Institute of Physics, Ilmenau University of Technology, Ilmenau, D-98684, Germany
| | - João Pedro de Almeida Martins
- Centre of Physics and Engineering of Advanced Materials, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Pedro J Sebastião
- Centre of Physics and Engineering of Advanced Materials, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Maria José Jardim Beira
- Centre of Physics and Engineering of Advanced Materials, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Siegfried Stapf
- Department of Technical Physics II/Polymer Physics, Institute of Physics, Ilmenau University of Technology, Ilmenau, D-98684, Germany
| | - Fabián Vaca Chávez
- FAMAF - Universidad Nacional de Córdoba & IFEG-CONICET, Córdoba, Argentina
| | - Carlos Mattea
- Department of Technical Physics II/Polymer Physics, Institute of Physics, Ilmenau University of Technology, Ilmenau, D-98684, Germany
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Daniel CI, Vaca Chávez F, Portugal CAM, Crespo JG, Sebastião PJ. 1H NMR Relaxation Study of a Magnetic Ionic Liquid as a Potential Contrast Agent. J Phys Chem B 2015; 119:11740-7. [DOI: 10.1021/acs.jpcb.5b04772] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Carla I. Daniel
- REQUIMTE/LAQV,
Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisbon, Portugal
| | - Fabián Vaca Chávez
- FaMAF, Universidad Nacional de Córdoba, IFEG CONICET, X5016LAE Córdoba, Argentina
| | - Carla A. M. Portugal
- REQUIMTE/LAQV,
Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisbon, Portugal
| | - João G. Crespo
- REQUIMTE/LAQV,
Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisbon, Portugal
| | - Pedro J. Sebastião
- Center
of Physics and Engineering of Advanced Materials, Departamento de
Física Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
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de Almeida Martins JP, Chávez FV, Sebastião PJ. NMR molecular dynamics study of chromonic liquid crystals Edicol Sunset Yellow doped with salts. Magn Reson Chem 2014; 52:540-545. [PMID: 24975451 DOI: 10.1002/mrc.4091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 05/15/2014] [Accepted: 05/18/2014] [Indexed: 06/03/2023]
Abstract
We investigate the effect of monoatomic salts on the molecular dynamics in the nematic and isotropic phases formed by the chromonic liquid crystal Edicol Sunset Yellow. The study was carried out using proton nuclear magnetic resonance relaxometry. To analyse the effect of incorporation of additional sodium chloride or lithium chloride on the solutions' molecular dynamics, the spin-lattice relaxation time was measured for Larmor frequencies between 10 kHz and 100 MHz. In the nematic phase, the presence of additional sodium or lithium ions seems to contribute to an increase of the rotations/reorientations corr elation times in comparison with the mixture without extra ions. The collective motions detected by proton NMR relaxometry are associated with collective fluctuations of molecules within the stacks in the nematic phase and with order parameter fluctuations in the isotropic phase.
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Affiliation(s)
- João P de Almeida Martins
- Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
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Cabaço MI, Besnard M, Chávez FV, Pinaud N, Sebastião PJ, Coutinho JAP, Danten Y. Understanding chemical reactions of CO2and its isoelectronic molecules with 1-butyl-3-methylimidazolium acetate by changing the nature of the cation: The case of CS2in 1-butyl-1-methylpyrrolidinium acetate studied by NMR spectroscopy and density functional theory calculations. J Chem Phys 2014; 140:244307. [DOI: 10.1063/1.4884820] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Dias N, Shimizu K, Morgado P, Filipe EJM, Canongia Lopes JN, Vaca Chávez F. Charge Templates in Aromatic Plus Ionic Liquid Systems Revisited: NMR Experiments and Molecular Dynamics Simulations. J Phys Chem B 2014; 118:5772-80. [DOI: 10.1021/jp503130y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nuno Dias
- Departamento
de Física, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Karina Shimizu
- Centro
de Química Estrutural (CQE), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Pedro Morgado
- Centro
de Química Estrutural (CQE), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Eduardo J. M. Filipe
- Centro
de Química Estrutural (CQE), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - José N. Canongia Lopes
- Centro
de Química Estrutural (CQE), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Fabián Vaca Chávez
- Centro
de Física da Matéria Condensada (CFMC), Universidade de Lisboa, 1649-004 Lisboa, Portugal
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Daniel CI, Vaca Chávez F, Feio G, Portugal CAM, Crespo JG, Sebastião PJ. 1H NMR Relaxometry, Viscometry, and PFG NMR Studies of Magnetic and Nonmagnetic Ionic Liquids. J Phys Chem B 2013; 117:11877-84. [DOI: 10.1021/jp4078536] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Carla I. Daniel
- REQUIMTE/CQFB,
Departamento de Quı́mica, Faculdade de Cien̂cias
e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - Fabián Vaca Chávez
- Condensed
Matter Physics Centre, University of Lisbon, Av. Prof. Gama Pinto 2, 1649-003 Lisbon, Portugal
| | - Gabriel Feio
- CENIMAT
- Centro de Investigação em Materiais, Faculdade de
Cien̂cias e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829-516 Caparica, Portugal
| | - Carla A. M. Portugal
- REQUIMTE/CQFB,
Departamento de Quı́mica, Faculdade de Cien̂cias
e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - João G. Crespo
- REQUIMTE/CQFB,
Departamento de Quı́mica, Faculdade de Cien̂cias
e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - Pedro J. Sebastião
- Condensed
Matter Physics Centre, University of Lisbon, Av. Prof. Gama Pinto 2, 1649-003 Lisbon, Portugal
- Departamento
de Física, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco
Pais, 1049-001 Lisbon, Portugal
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Isabel Cabaço M, Besnard M, Chávez FV, Pinaud N, Sebastião PJ, Coutinho JAP, Mascetti J, Danten Y. On the chemical reactions of carbon dioxide isoelectronic molecules CS2 and OCS with 1-butyl-3-methylimidazolium acetate. Chem Commun (Camb) 2013; 49:11083-5. [DOI: 10.1039/c3cc46038j] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Besnard M, Cabaço MI, Vaca Chávez F, Pinaud N, Sebastião PJ, Coutinho JAP, Mascetti J, Danten Y. CO2 in 1-Butyl-3-methylimidazolium Acetate. 2. NMR Investigation of Chemical Reactions. J Phys Chem A 2012; 116:4890-901. [DOI: 10.1021/jp211689z] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Marcel Besnard
- GSM Institut des Sciences Moléculaires,
CNRS (UMR 5255), Université Bordeaux I, 351, Cours de la Libération 33405 Talence Cedex, France
| | - M. Isabel Cabaço
- Departamento de
Física, Instituto Superior Técnico, UTL, Av. Rovisco Pais 1049-001 Lisboa, Portugal
- Centro de Física Atómica da UL, Av. Prof. Gama Pinto 2, 1649-003
Lisboa, Portugal
| | - Fabián Vaca Chávez
- Centro de Física da Matéria Condensada da UL, Av. Prof. Gama Pinto
2, 1694-003 Lisboa, Portugal
| | - Noël Pinaud
- CESAMO Institut des Sciences
Moléculaires, CNRS (UMR 5255), Université Bordeaux I, 351, Cours de la Libération 33405
Talence Cedex, France
| | - Pedro J. Sebastião
- Departamento de
Física, Instituto Superior Técnico, UTL, Av. Rovisco Pais 1049-001 Lisboa, Portugal
- Centro de Física da Matéria Condensada da UL, Av. Prof. Gama Pinto
2, 1694-003 Lisboa, Portugal
| | - João A. P. Coutinho
- CICECO, Departamento de
Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal
| | - Joëlle Mascetti
- GSM Institut des Sciences Moléculaires,
CNRS (UMR 5255), Université Bordeaux I, 351, Cours de la Libération 33405 Talence Cedex, France
| | - Yann Danten
- GSM Institut des Sciences Moléculaires,
CNRS (UMR 5255), Université Bordeaux I, 351, Cours de la Libération 33405 Talence Cedex, France
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Vaca Chávez F, Sebastião PJ, Miyake Y, Monobe H, Shimizu Y. Dynamics of Discotic Fluoroalkylated Triphenylene Molecules Studied by Proton NMR Relaxometry. J Phys Chem B 2012; 116:2339-46. [DOI: 10.1021/jp206225t] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Pedro J. Sebastião
- Condensed Matter Physics Centre, University of Lisbon, Lisbon, Portugal
- Departamento de Física, Instituto Superior
Técnico, Technical University of Lisbon, Lisbon, Portugal
| | - Yasuo Miyake
- National Institute of Advanced Industrial Science and Technology, Kansai Center, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
| | - Hirosato Monobe
- National Institute of Advanced Industrial Science and Technology, Kansai Center, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
| | - Yo Shimizu
- National Institute of Advanced Industrial Science and Technology, Kansai Center, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
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Besnard M, Cabaço MI, Chávez FV, Pinaud N, Sebastião PJ, Coutinho JAP, Danten Y. On the spontaneous carboxylation of 1-butyl-3-methylimidazolium acetate by carbon dioxide. Chem Commun (Camb) 2012; 48:1245-7. [DOI: 10.1039/c1cc16702b] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Affiliation(s)
- Fabián Vaca Chávez
- Institut für Physik − NMR, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 7, D-06120 Halle, Germany
| | - Kay Saalwächter
- Institut für Physik − NMR, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 7, D-06120 Halle, Germany
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Vaca Chávez F, Saalwächter K. Time-Domain NMR Observation of Entangled Polymer Dynamics: Universal Behavior of Flexible Homopolymers and Applicability of the Tube Model. Macromolecules 2011. [DOI: 10.1021/ma1025708] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fabián Vaca Chávez
- Institut für Physik − NMR, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 7, D-06120 Halle, Germany
| | - Kay Saalwächter
- Institut für Physik − NMR, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 7, D-06120 Halle, Germany
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Vaca Chávez F, Saalwächter K. NMR observation of entangled polymer dynamics: tube model predictions and constraint release. Phys Rev Lett 2010; 104:198305. [PMID: 20867007 DOI: 10.1103/physrevlett.104.198305] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Indexed: 05/29/2023]
Abstract
We use a benchtop NMR technique to monitor entangled polymer melt dynamics over 5 decades in time covering regimes II-IV of the tube model. We confirm the familiar molar mass scaling exponents of the regime transitions, but we observe a mass-dependent time scaling exponent describing segmental fluctuations in the constrained-Rouse regime II up to high molecular weights. Local chain motions are thus governed by modes that are much less restricted than predicted by the tube model. Diluting protonated chains in deuterated invisible matrix chains, we prove that the exponent is determined by the matrix molecular weight, suggesting constraint-release effects as the origin.
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Affiliation(s)
- Fabián Vaca Chávez
- Institut für Physik-NMR, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Straße 7, D-06120 Halle, Germany
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Ok S, Steinhart M, Serbescu A, Franz C, Vaca Chávez F, Saalwächter K. Confinement Effects on Chain Dynamics and Local Chain Order in Entangled Polymer Melts. Macromolecules 2010; 43:4429-4434. [PMID: 20502536 PMCID: PMC2875088 DOI: 10.1021/ma1003248] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 04/13/2010] [Indexed: 11/29/2022]
Affiliation(s)
- Salim Ok
- Institut für Chemie, Universität Osnabrück, Barbarastr. 7, D-46069 Osnabrück, Germany
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Vaca Chávez F, Schönhoff M. Pore size distributions in polyelectrolyte multilayers determined by nuclear magnetic resonance cryoporometry. J Chem Phys 2007; 126:104705. [PMID: 17362079 DOI: 10.1063/1.2565841] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Polyelectrolyte multilayers (PEMs) are thin films, which are assembled one molecular layer at a time, by alternatingly adsorbing polycations and polyanions making use of their attractive electrostatic interaction. Since the porosity of PEMs is one of the properties of major interest, in the current work the first pore size distribution of PEMs in samples consisting of silica particles coated with poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) is presented. To this end, the nuclear magnetic resonance (NMR) cryoporometry technique was applied. The proton NMR signal of liquid water is analyzed assuming a log normal distribution of motional correlation times. From the results, it is possible to determine the size of water sites in the layers to around 1 nm. In addition, a slight variation with the number of layers is found. The average pore size agrees with cutoff sizes found in permeation experiments.
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Affiliation(s)
- Fabián Vaca Chávez
- Institute of Physical Chemistry, University of Münster, Corrensstrasse 30, D-48149 Münster, Germany.
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