Nafion

Last updated
Nafion
Nafion2.svg
Identifiers
ChemSpider
  • none
PubChem CID
Properties
C7HF13O5S . C2F4
Molar mass See Article
Hazards
GHS labelling:
GHS-pictogram-exclam.svg
Warning
H319, H335
P261, P264, P271, P280, P304+P340, P305+P351+P338, P312, P337+P313, P403+P233, P405, P501
Related compounds
Related compounds
Aciplex
Flemion
Dowex
fumapem F
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Nafion is a brand name for a sulfonated tetrafluoroethylene based fluoropolymer-copolymer synthesized in 1962 by Dr. Donald J. Connolly at the DuPont Experimental Station in Wilmington Delaware (U.S. Patent 3,282,875). Additional work on the polymer family was performed in the late 1960s by Dr. Walther Grot of DuPont. [1] Nafion is a brand of the Chemours company. It is the first of a class of synthetic polymers with ionic properties that are called ionomers. Nafion's unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene (PTFE) backbone. [2] [3] [4] Nafion has received a considerable amount of attention as a proton conductor for proton exchange membrane (PEM) fuel cells because of its excellent chemical and mechanical stability in the harsh conditions of this application.

Contents

The chemical basis of Nafion's ion-conductive properties remain a focus of extensive research. [2] Ion conductivity of Nafion increases with the level of hydration. Exposure of Nafion to a humidified environment or liquid water increases the amount of water molecules associated with each sulfonic acid group. The hydrophilic nature of the ionic groups attract water molecules, which begin to solvate the ionic groups and dissociate the protons from the -SO3H (sulfonic acid) group. The dissociated protons "hop" from one acid site to another through mechanisms facilitated by the water molecules and hydrogen bonding. [2] Upon hydration, Nafion phase-separates at nanometer length scales resulting in formation of an interconnected network of hydrophilic domains which allow movement of water and cations, but the membranes do not conduct electrons and minimally conduct anions due to permselectivity (charge-based exclusion). Nafion can be manufactured with or exchanged to alternate cation forms for different applications (e.g. lithiated for Li-ion batteries) and at different equivalent weights (EWs), alternatively considered as ion-exchange capacities (IECs), to achieve a range of cationic conductivities with trade-offs to other physicochemical properties such as water uptake and swelling.

Nomenclature and molecular weight

Nafion can be produced as both a powder resin and a copolymer. It has various chemical configurations and thus several chemical names in the IUPAC system. Nafion-H, for example, includes the following systematic names:

The molecular weight of Nafion is variable due to differences in processing and solution morphology. [3] [4] The structure of a Nafion unit illustrates the variability of the material; for example, the most basic monomer contains chain variation between the ether groups (the z subscript). Conventional methods of determining molecular weight such as light scattering and gel permeation chromatography are not applicable because Nafion is insoluble, although the molecular weight has been estimated at 105–106 Da. [3] [4] Instead, the equivalent weight (EW) and material thickness are used to describe most commercially available membranes. The EW is the number of grams of dry Nafion per mole of sulfonic acid groups when the material is in the acid form. [4] Nafion membranes are commonly categorized in terms of their EW and thickness. [2] [5] For example, Nafion 117 indicates an extrusion-cast membrane with 1100 g/mol EW and 0.007 inches (7 thou) in thickness. [5] In contrast to equivalent weight, conventional ion-exchange resins are usually described in terms of their ion exchange capacity (IEC), which is the multiplicative inverse or reciprocal of the equivalent weight, i.e., IEC = 1000/EW.

Preparation

Nafion derivatives are first synthesized by the copolymerization of tetrafluoroethylene (TFE) (the monomer in Teflon) and a derivative of a perfluoro (alkyl vinyl ether) with sulfonyl acid fluoride. The latter reagent can be prepared by the pyrolysis of its respective oxide or carboxylic acid to give the olefinated structure. [6]

The resulting product is an -SO2F-containing thermoplastic that is extruded into films. Hot aqueous NaOH converts these sulfonyl fluoride (-SO2F) groups into sulfonate groups (-SO3−Na+). This form of Nafion, referred to as the neutral or salt form, is finally converted to the acid form containing the sulfonic acid (-SO3H) groups. Nafion can be dispersed into solution by heating in aqueous alcohol at 250 °C in an autoclave for subsequent casting into thin films or use as polymeric binder in electrodes. By this process, Nafion can be used to generate composite films, coat electrodes, or repair damaged membranes. [3]

Properties

The combination of the stable PTFE backbone with the acidic sulfonic groups gives Nafion its characteristics: [2] [7]

Structure/morphology

The morphology of Nafion membranes is a matter of continuing study to allow for greater control of its properties. Other properties such as water management, hydration stability at high temperatures, electro-osmotic drag, as well as the mechanical, thermal, and oxidative stability, are affected by the Nafion structure. A number of models have been proposed for the morphology of Nafion to explain its unique transport properties. [2]

Cluster-network model Cluster network model.png
Cluster-network model

The first model for Nafion, called the cluster-channel or cluster-network model, consisted of an equal distribution of sulfonate ion clusters (also described as 'inverted micelles' [4] ) with a 40 Å (4 nm) diameter held within a continuous fluorocarbon lattice. Narrow channels about 10 Å (1 nm) in diameter interconnect the clusters, which explains the transport properties. [3] [4] [12]

The difficulty in determining the exact structure of Nafion stems from inconsistent solubility and crystalline structure among its various derivatives. Advanced morphological models have included a core-shell model where the ion-rich core is surrounded by an ion poor shell, a rod model where the sulfonic groups arrange into crystal-like rods, and a sandwich model where the polymer forms two layers whose sulfonic groups attract across an aqueous layer where transport occurs. [4] Consistency between the models include a network of ionic clusters; the models differ in the cluster geometry and distribution. Although no model has yet been determined fully correct, some scientists have demonstrated that as the membrane hydrates, Nafion's morphology transforms from the cluster-channel model to a rod-like model. [4]

A cylindrical-water channel model [13] was also proposed based on simulations of small-angle X-ray scattering data and solid state nuclear magnetic resonance studies. In this model, the sulfonic acid functional groups self-organize into arrays of hydrophilic water channels, each ~ 2.5 nm in diameter, through which small ions can be easily transported. Interspersed between the hydrophilic channels are hydrophobic polymer backbones that provide the observed mechanical stability. Many recent studies, however, favored a phase-separated nanostructure consisting of locally-flat, or ribbon-like, hydrophilic domains based on evidence from direct-imaging studies [14] and more comprehensive analysis of the structure and transport properties. [2] [15]

Applications

Nafion's properties make it suitable for a broad range of applications. Nafion has found use in fuel cells, electrochemical devices, chlor-alkali production, metal-ion recovery, water electrolysis, plating, surface treatment of metals, batteries, sensors, Donnan dialysis cells, drug release, gas drying or humidification, and superacid catalysis for the production of fine chemicals. [3] [4] [7] [16] Nafion is also often cited for theoretical potential (i.e., thus far untested) in a number of fields. With consideration of Nafion's wide functionality, only the most significant will be discussed below.

Chlor-alkali production cell membrane

A chlor-alkali cell Chlor alkali cell.png
A chlor-alkali cell

Chlorine and sodium/potassium hydroxide are among the most produced commodity chemicals in the world. Modern production methods produce Cl2 and NaOH/KOH from the electrolysis of brine using a Nafion membrane between half-cells. Before the use of Nafion, industries used mercury containing sodium amalgam to separate sodium metal from cells or asbestos diaphragms to allow for transfer of sodium ions between half cells; both technologies were developed in the latter half of the 19th century. The disadvantages of these systems is worker safety and environmental concerns associated with mercury and asbestos, economical factors also played a part, and in the diaphragm process chloride contamination of the hydroxide product. Nafion was the direct result of the chlor-alkali industry addressing these concerns; Nafion could tolerate the high temperatures, high electrical currents, and corrosive environment of the electrolytic cells. [3] [4] [7]

The figure to the right shows a chlor-alkali cell where Nafion functions as a membrane between half cells. The membrane allows sodium ions to transfer from one cell to the other with minimal electrical resistance. The membrane was also reinforced with additional membranes to prevent gas product mixing and minimize back transfer of Cl− and −OH ions. [3]

Proton exchange membrane (PEM) for fuel cells

Although fuel cells have been used since the 1960s as power supplies for satellites, recently they have received renewed attention for their potential to efficiently produce clean energy from hydrogen. Nafion was found effective as a membrane for proton exchange membrane (PEM) fuel cells by permitting hydrogen ion transport while preventing electron conduction. Solid Polymer Electrolytes, which are made by connecting or depositing electrodes (usually noble metal) to both sides of the membrane, conduct the electrons through an energy requiring process and rejoin the hydrogen ions to react with oxygen and produce water. [3] Fuel cells are expected to find strong use in the transportation industry.

Superacid catalyst for fine chemical production

Nafion, as a superacid, has potential as a catalyst for organic synthesis. Studies have demonstrated catalytic properties in alkylation, isomerization, oligomerization, acylation, ketalization, esterification, hydrolysis of sugars and ethers, and oxidation. New applications are constantly being discovered. [16] These processes, however, have not yet found strong commercial use. Several examples are shown below:

Alkylation with alkyl halides

Nafion-H gives efficient conversion whereas the alternative method, which employs Friedel-Crafts synthesis, can promote polyalkylation: [17]

Nafion alkylation halides.png

Acylation

The amount of Nafion-H needed to catalyze the acylation of benzene with aroyl chloride is 10–30% less than the Friedel-Crafts catalyst: [17]

Nafion acylation benzene.png

Catalysis of protection groups

Nafion-H increases reaction rates of protection via dihydropyran or o-trialkylsilation of alcohols, phenol, and carboxylic acids. [16]

Nafion protection.png

Isomerization

Nafion can catalyze a 1,2-hydride shift. [16]

Nafion isomerize.png

It is possible to immobilize enzymes within the Nafion by enlarging pores with lipophilic salts. Nafion maintains a structure and pH to provide a stable environment for the enzymes. Applications include catalytic oxidation of adenine dinucleotides. [16]

Sensors

Nafion has found use in the production of sensors, with application in ion-selective, metallized, optical, and biosensors. What makes Nafion especially interesting is its demonstration in biocompatibility. Nafion has been shown to be stable in cell cultures as well as the human body, and there is considerable research towards the production of higher sensitivity glucose sensors. [3]

Antimicrobial surfaces

Nafion surfaces show an exclusion zone against bacteria colonization. [18] Moreover, layer-by-layer coatings comprising Nafion show excellent antimicrobial properties. [19]

Dehumidification in spacecraft

The SpaceX Dragon 2 human-rated spacecraft uses Nafion membranes to dehumidify the cabin air. One side of the membrane is exposed to the cabin atmosphere, the other to the vacuum of space. This results in dehumidification since Nafion is permeable to water molecules but not air. This saves power and complexity since cooling is not required (as needed with a condensing dehumidifier), and the removed water is rejected to space with no additional mechanism needed. [20]

Modified Nafion for PEM fuel cells

Normal Nafion will dehydrate (thus lose proton conductivity) when the temperature is above ~80 °C. This limitation troubles the design of fuel cells because higher temperatures are desirable for better efficiency and CO tolerance of the platinum catalyst. Silica and zirconium phosphate can be incorporated into Nafion water channels through in situ chemical reactions to increase the working temperature to above 100 °C.[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Proton-exchange membrane fuel cell</span> Power generation technology

Proton-exchange membrane fuel cells (PEMFC), also known as polymer electrolyte membrane (PEM) fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges and a special proton-conducting polymer electrolyte membrane. PEMFCs generate electricity and operate on the opposite principle to PEM electrolysis, which consumes electricity. They are a leading candidate to replace the aging alkaline fuel-cell technology, which was used in the Space Shuttle.

An artificial membrane, or synthetic membrane, is a synthetically created membrane which is usually intended for separation purposes in laboratory or in industry. Synthetic membranes have been successfully used for small and large-scale industrial processes since the middle of the twentieth century. A wide variety of synthetic membranes is known. They can be produced from organic materials such as polymers and liquids, as well as inorganic materials. Most commercially utilized synthetic membranes in industry are made of polymeric structures. They can be classified based on their surface chemistry, bulk structure, morphology, and production method. The chemical and physical properties of synthetic membranes and separated particles as well as separation driving force define a particular membrane separation process. The most commonly used driving forces of a membrane process in industry are pressure and concentration gradient. The respective membrane process is therefore known as filtration. Synthetic membranes utilized in a separation process can be of different geometry and flow configurations. They can also be categorized based on their application and separation regime. The best known synthetic membrane separation processes include water purification, reverse osmosis, dehydrogenation of natural gas, removal of cell particles by microfiltration and ultrafiltration, removal of microorganisms from dairy products, and dialysis.

<span class="mw-page-title-main">Proton conductor</span> Type of electrolyte

A proton conductor is an electrolyte, typically a solid electrolyte, in which H+ are the primary charge carriers.

<span class="mw-page-title-main">Sulfonic acid</span> Organic compounds with the structure R−S(=O)2−OH

In organic chemistry, sulfonic acid refers to a member of the class of organosulfur compounds with the general formula R−S(=O)2−OH, where R is an organic alkyl or aryl group and the S(=O)2(OH) group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound is the parent sulfonic acid, HS(=O)2(OH), a tautomer of sulfurous acid, S(=O)(OH)2. Salts or esters of sulfonic acids are called sulfonates.

Polybenzimidazole (PBI, short for poly[2,2’-(m-phenylen)-5,5’-bisbenzimidazole]) fiber is a synthetic fiber with a very high decomposition temperature. It does not exhibit a melting point, it has exceptional thermal and chemical stability, and it does not readily ignite. It was first discovered by American polymer chemist Carl Shipp Marvel in the pursuit of new materials with superior stability, retention of stiffness, and toughness at elevated temperature. Due to its high stability, polybenzimidazole is used to fabricate high-performance protective apparel such as firefighter's gear, astronaut space suits, high temperature protective gloves, welders’ apparel and aircraft wall fabrics. Polybenzimidazole has been applied as a membrane in fuel cells.

An ionomer is a polymer composed of repeat units of both electrically neutral repeating units and ionized units covalently bonded to the polymer backbone as pendant group moieties. Usually no more than 15 mole percent are ionized. The ionized units are often carboxylic acid groups.

A proton-exchange membrane, or polymer-electrolyte membrane (PEM), is a semipermeable membrane generally made from ionomers and designed to conduct protons while acting as an electronic insulator and reactant barrier, e.g. to oxygen and hydrogen gas. This is their essential function when incorporated into a membrane electrode assembly (MEA) of a proton-exchange membrane fuel cell or of a proton-exchange membrane electrolyser: separation of reactants and transport of protons while blocking a direct electronic pathway through the membrane.

<span class="mw-page-title-main">Polystyrene sulfonate</span> Drug class

Polystyrene sulfonates are a group of medications used to treat high blood potassium. Effects generally take hours to days. They are also used to remove potassium, calcium, and sodium from solutions in technical applications.

<span class="mw-page-title-main">Electrolysis of water</span> Electricity-induced chemical reaction

Electrolysis of water is using electricity to split water into oxygen and hydrogen gas by electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, but must be kept apart from the oxygen as the mixture would be extremely explosive. Separately pressurised into convenient 'tanks' or 'gas bottles', hydrogen can be used for oxyhydrogen welding and other applications, as the hydrogen / oxygen flame can reach approximately 2,800°C.

<span class="mw-page-title-main">Fast-ion conductor</span>

In materials science, fast ion conductors are solid conductors with highly mobile ions. These materials are important in the area of solid state ionics, and are also known as solid electrolytes and superionic conductors. These materials are useful in batteries and various sensors. Fast ion conductors are used primarily in solid oxide fuel cells. As solid electrolytes they allow the movement of ions without the need for a liquid or soft membrane separating the electrodes. The phenomenon relies on the hopping of ions through an otherwise rigid crystal structure.

<span class="mw-page-title-main">Polyphosphazene</span>

Polyphosphazenes include a wide range of hybrid inorganic-organic polymers with a number of different skeletal architectures with the backbone P-N-P-N-P-N-. In nearly all of these materials two organic side groups are attached to each phosphorus center. Linear polymers have the formula (N=PR1R2)n, where R1 and R2 are organic (see graphic). Other architectures are cyclolinear and cyclomatrix polymers in which small phosphazene rings are connected together by organic chain units. Other architectures are available, such as block copolymer, star, dendritic, or comb-type structures. More than 700 different polyphosphazenes are known, with different side groups (R) and different molecular architectures. Many of these polymers were first synthesized and studied in the research group of Harry R. Allcock.

The Glossary of fuel cell terms lists the definitions of many terms used within the fuel cell industry. The terms in this fuel cell glossary may be used by fuel cell industry associations, in education material and fuel cell codes and standards to name but a few.

<span class="mw-page-title-main">2-Acrylamido-2-methylpropane sulfonic acid</span> Chemical compound

2-Acrylamido-2-methylpropane sulfonic acid (AMPS) was a Trademark name by The Lubrizol Corporation. It is a reactive, hydrophilic, sulfonic acid acrylic monomer used to alter the chemical properties of wide variety of anionic polymers. In the 1970s, the earliest patents using this monomer were filed for acrylic fiber manufacturing. Today, there are over several thousands patents and publications involving use of AMPS in many areas including water treatment, oil field, construction chemicals, hydrogels for medical applications, personal care products, emulsion coatings, adhesives, and rheology modifiers. Lubrizol discontinued the production of this monomer in 2017 due to copy-cat production from China and India destroying the profitability of this product.

<span class="mw-page-title-main">Alkaline anion-exchange membrane fuel cell</span>

An alkaline anion-exchange membrane fuel cell (AAEMFC), also known as anion-exchange membrane fuel cells (AEMFCs), alkaline membrane fuel cells (AMFCs), hydroxide-exchange membrane fuel cells (HEMFCs), or solid alkaline fuel cells (SAFCs) is a type of alkaline fuel cell that uses an anion-exchange membrane to separate the anode and cathode compartments.

Richard Yeo Swee Chye is an American scientist with 17 U.S. patents, best known for his research on disposable diapers.

<span class="mw-page-title-main">Proton exchange membrane electrolysis</span> Technology for splitting water molecules

Proton exchange membrane(PEM) electrolysis is the electrolysis of water in a cell equipped with a solid polymer electrolyte (SPE) that is responsible for the conduction of protons, separation of product gases, and electrical insulation of the electrodes. The PEM electrolyzer was introduced to overcome the issues of partial load, low current density, and low pressure operation currently plaguing the alkaline electrolyzer. It involves a proton-exchange membrane.

<span class="mw-page-title-main">Vinylsulfonic acid</span> Chemical compound

Vinylsulfonic acid is the organosulfur compound with the chemical formula CH2=CHSO3H. It is the simplest unsaturated sulfonic acid. The C=C double bond is a site of high reactivity. Polymerization gives polyvinylsulfonic acid, especially when used as a comonomer with functionalized vinyl and (meth)acrylic acid compounds. It is a colorless, water-soluble liquid, although commercial samples can appear yellow or even red.

<span class="mw-page-title-main">Amalie Frischknecht</span> American theoretical polymer physicist

Amalie L. Frischknecht is an American theoretical polymer physicist at Sandia National Laboratories in Albuquerque, New Mexico. She was elected a fellow of the American Physical Society (APS) in 2012 for "her outstanding contributions to the theory of ionomers and nanocomposites including the development and application of density functional theory to polymers". Her research focuses on understanding the structure, phase behavior, and self-assembly of polymer systems, such as complex fluids polymer nanocomposites, lipid bilayer assemblies, and ionomers.

A polymer electrolyte is a polymer matrix capable of ion conduction. Much like other types of electrolyte—liquid and solid-state—polymer electrolytes aid in movement of charge between the anode and cathode of a cell. The use of polymers as an electrolyte was first demonstrated using dye-sensitized solar cells. The field has expanded since and is now primarily focused on the development of polymer electrolytes with applications in batteries, fuel cells, and membranes.

<span class="mw-page-title-main">Anion exchange membrane electrolysis</span> Splitting of water using a semipermeable membrane

Anion exchange membrane(AEM) electrolysis is the electrolysis of water that utilises a semipermeable membrane that conducts hydroxide ions (OH−) called an anion exchange membrane. Like a proton-exchange membrane (PEM), the membrane separates the products, provides electrical insulation between electrodes, and conducts ions. Unlike PEM, AEM conducts hydroxide ions. The major advantage of AEM water electrolysis is that a high-cost noble metal catalyst is not required, low-cost transition metal catalyst can be used instead. AEM electrolysis is similar to alkaline water electrolysis, which uses a non-ion-selective separator instead of an anion-exchange membrane.

References

  1. ↑ Church, Steven (January 6, 2006). "Del. firm installs fuel cell". The News Journal . p. B7.
  2. 1 2 3 4 5 6 7 8 9 Kusoglu, Ahmet; Weber, Adam Z. (2017-02-08). "New Insights into Perfluorinated Sulfonic-Acid Ionomers". Chemical Reviews. 117 (3): 987–1104. doi: 10.1021/acs.chemrev.6b00159 . ISSN   0009-2665. PMID   28112903.
  3. 1 2 3 4 5 6 7 8 9 10 Heitner-Wirguin, C. (1996). "Recent advances in perfluorinated ionomer membranes: structure, properties and applications". Journal of Membrane Science . 120: 1–33. doi:10.1016/0376-7388(96)00155-X.
  4. 1 2 3 4 5 6 7 8 9 10 Mauritz, Kenneth A.; Moore, Robert B. (2004). "State of Understanding of Nafion". Chemical Reviews. 104 (10): 4535–4586. doi:10.1021/cr0207123. PMID   15669162.
  5. 1 2 "nafion membrane, chemours nafion, proton exchange membrane". www.nafion.com. Retrieved 2021-04-22.
  6. ↑ Connolly, D.J.; Longwood; Gresham, W. F. (1966). "Fluorocarbon Vinyl Ether Polymers". Google Patents . U.S. patent 3,282,875 .
  7. 1 2 3 Perma Pure LLC (2004). "Nafion: Physical and Chemical Properties". Technical Notes and Articles. Archived from the original on September 28, 2013.
  8. ↑ Schuster, M., Ise, M., Fuchs, A., Kreuer, K.D., Maier, J. (2005). "Proton and Water Transport in Nano-separated Polymer Membranes" (PDF). Le Journal de Physique IV. 10. Germany: Max-Planck-Institut für Festkörperforschung: Pr7-279-Pr7-281. doi:10.1051/jp4:2000756. ISSN   1155-4339. Archived from the original on 2007-06-11.{{cite journal}}: CS1 maint: bot: original URL status unknown (link) CS1 maint: multiple names: authors list (link)
  9. ↑ Sone, Yoshitsugu; Ekdunge, Per; Simonsson, Daniel (1996-04-01). "Proton Conductivity of Nafion 117 as Measured by a Four-Electrode AC Impedance Method". Journal of the Electrochemical Society. 143 (4): 1254. Bibcode:1996JElS..143.1254S. doi:10.1149/1.1836625. ISSN   1945-7111.
  10. ↑ Schalenbach, Maximilian; Hoefner, Tobias; Paciok, Paul; Carmo, Marcelo; Lueke, Wiebke; Stolten, Detlef (2015-10-28). "Gas Permeation through Nafion. Part 1: Measurements". The Journal of Physical Chemistry C. 119 (45): 25145–25155. doi:10.1021/acs.jpcc.5b04155.
  11. ↑ Schalenbach, Maximilian; Hoeh, Michael A.; Gostick, Jeff T.; Lueke, Wiebke; Stolten, Detlef (2015-10-14). "Gas Permeation through Nafion. Part 2: Resistor Network Model". The Journal of Physical Chemistry C. 119 (45): 25156–25169. doi:10.1021/acs.jpcc.5b04157.
  12. ↑ Gierke, T. D.; Munn, G. E.; Wilson, F. C. (1981). "The morphology in nafion perfluorinated membrane products, as determined by wide- and small-angle x-ray studies". Journal of Polymer Science: Polymer Physics Edition. 19 (11): 1687–1704. Bibcode:1981JPoSB..19.1687G. doi:10.1002/pol.1981.180191103.
  13. ↑ Schmidt-Rohr, K.; Chen, Q. (2007). "Parallel cylindrical water nanochannels in Nafion fuel-cell membranes". Nature Materials. 7 (1): 75–83. doi:10.1038/nmat2074. PMID   18066069.
  14. ↑ Allen, Frances I.; Comolli, Luis R.; Kusoglu, Ahmet; Modestino, Miguel A.; Minor, Andrew M.; Weber, Adam Z. (2015-01-20). "Morphology of Hydrated As-Cast Nafion Revealed through Cryo Electron Tomography". ACS Macro Letters. 4 (1): 1–5. doi: 10.1021/mz500606h . ISSN   2161-1653. PMID   35596390.
  15. ↑ Kreuer, Klaus-Dieter; Portale, Giuseppe (2013-11-20). "A Critical Revision of the Nano-Morphology of Proton Conducting Ionomers and Polyelectrolytes for Fuel Cell Applications". Advanced Functional Materials. 23 (43): 5390–5397. doi:10.1002/adfm.201300376. S2CID   94579140.
  16. 1 2 3 4 5 Gelbard, Georges (2005). "Organic Synthesis by Catalysis with Ion-Exchange Resins". Industrial & Engineering Chemistry Research . 44 (23): 8468–8498. doi:10.1021/ie0580405.
  17. 1 2 El-Kattan, Y.; McAtee, J.; Nafion-H. (2001) "Nafion-H". In Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons, ISBN   978-0-470-01754-8.
  18. ↑ Cheng, Yifan; Moraru, Carmen I. (2018). "Long-range interactions keep bacterial cells from liquid-solid interfaces: Evidence of a bacteria exclusion zone near Nafion surfaces and possible implications for bacterial attachment". ColloidsSurf. B: Biointerfaces. 162: 16–24. doi: 10.1016/j.colsurfb.2017.11.016 . PMID   29132042.
  19. ↑ Gibbons, Ella N.; Winder, Charis; Barron, Elliot; et al. (2019). "Layer by Layer Antimicrobial Coatings Based on Nafion, Lysozyme, and Chitosan". Nanomaterials. 9 (1563): 1563. doi: 10.3390/nano9111563 . PMC   6915488 . PMID   31689966.
  20. ↑ Jason Silverman; Andrew Irby; Theodore Agerton (2020). Development of the Crew Dragon ECLSS (PDF). International Conference on Environmental Systems.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.