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Encyclopedia > Nafion
Nafion
Chemical Structure of Nafion
General
Systematic name See Article
Common names Nafion
Molecular formula C7HF13O5S . C2F4
Molar mass See Article
CAS number [31175-20-9]
Related compounds
Related compounds Aciplex
Flemion
Dowew
Fumasep
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

Nafion® is a sulfonated tetrafluorethylene copolymer discovered in the late 1960s by Walther Grot of DuPont de Nemours.[1] It is the first of a class of synthetic polymers with ionic properties which are called ionomers. Nafion's unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene (Teflon) backbone.[2][3] Nafion has received a considerable amount of attention as a proton conductor for proton exchange membrane (PEM) fuel cells because of its excellent thermal and mechanical stability. Image File history File links No higher resolution available. ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... This article does not cite its references or sources. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... A heteropolymer, also called a copolymer, is a polymer formed when two different types of monomer are linked in the same polymer chain. ... The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ... This article is about the DuPont company. ... An ionomer is a polyelectrolyte that comprises copolymers containing both electrically neutral repeating units and a fraction of ionic units (usually no more than 15%). Categories: Chemistry stubs | Polymers | Plastics ... Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene. ... A proton conductor is an electrolyte where movable hydrogen ions are the primary charge carriers. ...


The chemical basis of Nafion's superior conductive properties remain a focus of research. Protons on the SO3H (sulfonic acid) groups "hop" from one acid site to another. Pores allow movement of cations but the membranes do not conduct anions or electrons. Nafion can be manufactured with various cationic conductivities. It has been suggested that Sulfonic acid/Temp be merged into this article or section. ... A cation is an ion with positive charge. ... An artificial membrane, also called a synthetic membrane, is a membrane prepared for separation tasks in laboratory and industry. ... An anion is an ion with negative charge. ... e- redirects here. ...

Contents

Nomenclature and molecular weight

Nafion can be produced as both a powder resin and a copolymer and has therefore acquired several IUPAC names. Nafion-H, for example, includes the following systematic names: Insect trapped in resin. ... A heteropolymer, also called a copolymer, is a polymer formed when two different types of monomer are linked in the same polymer chain. ... The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ...

  • From Chemical Abstracts: ethanesulfonyl fluoride, 2-[1-[difluoro-[(trifluoroethenyl)oxy]methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2,-tetrafluoro-, with tetrafluoroethylene
  • tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer

The molecular weight of Nafion is uncertain due to differences in processing and solution morphology.[2][3] The structure of a Nafion unit, shown at the top of the page, 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 of course insoluble, although the molecular weight has been estimated at 105-106 Da. [2][3] Instead, the equivalent weight (EW) and material thickness are used to describe most commercially available membranes. The EW is defined as the weight of Nafion per mole of sulfonic acid group.[3] For example, Nafion 117 represents 1100 g EW + 0.007 in thickness. In contrast equivalent weight, conventional ion-exchange resins are usually described in terms of their ion exchange capacity (IEC) which is inversely proportional to the equivalent weight. Chemical Abstracts Service (CAS) is a division of the American Chemical Society which produces the Chemical Abstracts, an index of the scientific literature in chemistry and related fields. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ... Ether is the general name for a class of chemical compounds which contain an ether group — an oxygen atom connected to two (substituted) alkyl groups. ... In particle physics, scattering is a class of phenomena by which particles are deflected by collisions with other particles. ... Gel permeation chromatography (GPC) also known as size exclusion chromatography (SEC) is a chromatographic method in which molecules are separated based on their size. ... It has been suggested that Sulfonic acid/Temp be merged into this article or section. ... Ion exchange resin beads An ion exchange resin is an insoluble matrix (or support structure) normally in the form of small (1-2 mm diameter) beads, usually white or yellowish, fabricated from an organic polymer substrate. ...


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.[4] Tetrafluoroethylene, or tetrafluoroethene, C2F4, is a compound of carbon and fluorine. ... Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene. ... Simple sketch of pyrolysis chemistry Pyrolysis usually means the chemical decomposition of organic materials by heating in the absence of oxygen or any other reagents, except possibly steam. ... An oxide is a chemical compound containing an oxygen atom and other elements. ... Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -C(=O)OH, usually written -COOH or -CO2H. [1] Carboxylic acids are Bronsted...


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 containin the sulfonic acid (-SO3H) groups. Nafion can be cast into thin films by heating in aqueous alcohol at 250 °C in an autoclave. By this process Nafion can be used to generate composite films, coat electrodes, or repair damaged membranes. [2] A thermoplastic is a material that is plastic or deformable, melts to a liquid when heated and freezes to a brittle, glassy state when cooled sufficiently. ... Extrusion is a manufacturing process used to create long objects of a fixed cross-sectional profile. ... Thin films are material layers of about 1 µm thickness. ... Front loading autoclaves are common Stovetop autoclaves need to be monitored carefully, but have a very large capacity Multiple large autoclaves are used for processing substantial quantities of laboratory equipment prior to reuse, and infectious material prior to disposal. ... An electrode is an electrical conductor used to make contact with a metallic part of a circuit (e. ...


Properties

The combination of the stable Teflon backbone with the acidic sulfonic groups gives Nafion its desirable characteristics: [5]

  • It is highly conductive to cations, making it ideal for many membrane applications.
  • It resists chemical attack. According to DuPont, only alkali metals (particularly sodium) can degrade Nafion under normal temperatures and pressures.
  • The Teflon backbone interlaced with the ionic sulfonate groups gives Nafion a high operating temperature, e.g. up to 190 °C.
  • It is a super-acid catalyst. The combination of fluorinated backbone, sulfonic acid groups, and the stabilizing effect of the polymer matrix make Nafion a very strong acid, with pKa ~ -6.[6] In this respect Nafion resembles the trifluoromethanesulfonic acid, CF3SO3H, although Nafion is a weaker acid by at least three orders of magnitude..
  • It is selectively and highly permeable to water. The degree of hydration of the Nafion membrane directly affects its ion conductivity and overall morphology.

This article is about the DuPont company. ... The alkali metals are the series of elements in Group 1 (IUPAC style) of the periodic table (excluding hydrogen in all but one rare circumstance): lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). ... A superacid is an acid with an acidity greater than that of 100% sulfuric acid. ... Trifluoromethanesulfonic acid, also known as triflic acid or TfOH, is a sulfonic acid with the chemical formula CF3SO3H . ...

Structure/morphology

The morphology of Nafion membranes is a matter of continuing study to allow for greater control on its properties. Other properties must be related to the Nafion structure such as water management, hydration stability at high temperatures, electro-osmotic drag, as well as the mechanical, thermal, and oxidative stability .

Cluster Network Model
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'[3]) with a 40 Š(4 nm) diameter held within a continuous fluorocarbon lattice. Narrow channels about 10 Š(1 nm) in diameter interconnect the clusters, which explains the transport properties. [2][3][7] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... An angstrom, angström, or ångström (symbol Å) is a unit of length. ... A nanometre (American spelling: nanometer) is 1. ...


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. [3] Consistency between the models include a network of ionic clusters; the models differ in the cluster geometry and distribution. Although no model was yet 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.[3]


Applications

Nafion's superior properties allowed for broad application. 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 humidifaction, and super-acid catalysis for the production of fine chemicals (Gelbard, 2005).[2][3][5][8] 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. Methanol fuel cell. ... In chemistry and manufacturing, electrolysis is a method of separating bonded elements and compounds by passing an electric current through them. ... This article or section is in need of attention from an expert on the subject. ... // Distinguish from censure and censer and censor. ...


Chlor-alkali production cell membrane

A Chlor-Alkali cell

Chlorine and sodium/potassium hydroxide are among the most produced commodity chemicals in the United States. 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, although economical factors also played a part. 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.[2][3][5] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Brine is water saturated or nearly saturated with salt. ... Fibrous asbestos on muscovite Asbestos Asbestos Asbestos (a misapplication of Latin: asbestos quicklime from Greek : a, not and sbestos, extinguishable) describes any of a group of minerals that can be fibrous, many of which are metamorphic and are hydrous magnesium silicates. ...


The figure to the right shows a chlor-alkai 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.[2]


Proton exchange membrane (PEM) for fuel cells

Although fuel cells have been used since the 1960's 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.[2] Fuel cells are expected to find strong use in the transportation industry. Proton-exchange fuel cells, also known as Polymer Electrolyte (Membrane) Fuel Cells (PEM or PEMFC) are low temperature fuel cells which are being developed for transport applications as well as for stationary applications. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ...


Superacid catalyst for fine chemical production

Nafion, as a superacid, has potential as a catalyst for organic synthesis. Studies have demonstrated catalystic properties in alkylation, isomerization, oligomerization, acylation, ketalization, esterification, hydrolysis of sugars and ethers, and oxidation. New applications are constantly being discovered.[8] These processes, however, have not yet found strong commercial use. Several examples are shown below: A superacid is an acid with an acidity greater than that of 100% sulfuric acid. ... Organic synthesis is the construction of organic molecules via chemical processes. ... Alkylation is the transfer of an alkyl group from one molecule to another. ... In chemistry, isomerization is the transformation of a molecule into a different isomer. ... In chemistry, an oligomer consists of a finite number of monomer units (oligo is Greek for a few), in contrast to a polymer which, at least in principle, consists of an infinite number of monomers. ... In chemistry, acylation is the process of adding an acyl group to a compound. ... Esterification is the general name for a chemical reaction in which two chemicals (typically an alcohol and an acid) form an ester as the reaction product. ... Hydrolysis is a chemical reaction or process in which a chemical compound reacts with water. ... This article deals with sugar as food and as an important, widely traded commodity; the word also has other uses; see Sugar (disambiguation) A sugar is a form of carbohydrate; the most commonly used sugar is a white crystalline solid, sucrose; used to alter the flavor and properties (mouthfeel, perservation... Ethers can refer to: In internet routing, the term associated with hosts In Organic chemistry, the plural of ether This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... The most fundamental reactions in chemistry are the redox processes. ...


Alkylation with alkyl halides
Nafion-H gives efficient conversion whereas the alternative method, which employs Friedel-Crafts synthesis, can promote polyalkylation:[9] The Friedel-Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. ...

Alkyl Halide Reaction


Acylation
The amount of Nafion-H needed catalyze the acylation of benzene with aroyl chloride is 10-30% less than the Friedel-Crafts catalyst: [9] Image File history File links No higher resolution available. ...

Acylation of Benzene


Catalysis of Protection groups
Nafion-H increases reaction rates of protection via dihydropyran or o-trialkylsilation of alcohols, phenol, and carboxylic acids.[8] Image File history File links No higher resolution available. ... Iron rusting - a chemical reaction with a slow reaction rate. ... A Protecting group or protective group is introduced into a molecule by chemical modification of a functional group in order to obtain chemoselectivity in a subsequent chemical reaction. ...

Catalysis of Protection groups


Isomerization
Nafion can catalyze a 1,2-hydride shift.[8] Image File history File links No higher resolution available. ... A 1,2-rearrangement or 1,2-shift or Whitmore 1,2-shift is a organic reaction where a substituent moves from one atom to another atom in a chemical compound. ...

Isomerization via Nafion

Recently scientists have been able to immobilize enzymes within the Nafion by enlarging pores with lipophilic salts. Nafion is able to maintain a structure and pH to provide a stable environment for the enzymes. Application has included catalytic oxidation of adenine dinucleotides.[8] Image File history File links No higher resolution available. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... This article or section does not cite its references or sources. ...


Sensors

Nafion has found use in the production of sensors, which application in ion-selective, metallicized, 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.[2] // Distinguish from censure and censer and censor. ... A biosensor is a device for the detection of an analyte that combines a biological component with a physicochemical detector component. ... Biocompatibility is the ability of a material to perform with an appropriate host response in a specific application. ... Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the term applied when cells are grown in a synthetic environment. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ...


References

  1. ^ Church, Steven. "Del. firm installs fuel cell", The News Journal, January 6, 2006, p. B7. 
  2. ^ a b c d e f g h i j 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 . 
  3. ^ a b c d e f g h i j Mauritz, K. A., Moore, R. B. (2004). "State of Understanding of Nafion". Chemical Reviews 104: 4535–4585. DOI:10.1021/cr0207123. 
  4. ^ Connolly, D.J.; Longwood; Gresham, W. F. (1966). "Fluorocarbon Vinyl Ether Polymers". U.S. Patent 3282875 . 
  5. ^ a b c
  6. ^ Schuster, M., Ise, M., Fuchs, A., Kreuer, K.D., Maier, J. (2005). "Proton and Water Transport in Nano-separated Polymer Membranes". Germany: Max-Planck-Institut für Festkörperforschung, n.d..
  7. ^ Gierke, T. D.; Munn, G. E.; Wilson, F. C. J. (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. DOI:10.1002/pol.1981.180191103. 
  8. ^ a b c d e Gelbard, Georges (2005). "Organic Synthesis by Catalysis with Ion-Exchange Resins". Industrial & Engineering Chemistry Research 44: 8468–8498. DOI:10.1021/ie0580405. 
  9. ^ a b El-Kattan, Y.; McAtee, J.; Nafion-H. (2001) Nafion-H. In Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons.

The Delaware News-Journal (also known as The News Journal) is a Wilmington, Delaware newspaper. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Chemical Reviews (usually abbreviated as ), is a peer-reviewed scientific journal, published since 1900 by the American Chemical Society. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Industrial & Engineering Chemistry Research (usually abbreviated as ), is a peer-reviewed scientific journal, published under this name since 1970 by the American Chemical Society; however, Industrial & Engineering Chemistry (1909-1970) is a forerunner of Industrial & Engineering Chemistry Research. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links


  Results from FactBites:
 
DuPont Fuel Cells | Products and Services | Nafion(r) Membranes and Dispersions (167 words)
For the past 30 years, DuPont™; Nafion® membranes and dispersions have been the product of choice for the fuel cell industry, providing unparalleled power output and durability.
Today, Nafion® polymer has evolved into a leading-edge fuel cell material for a wide variety of applications.
Advancements in durability and chemical stability mean that Nafion® membranes are more resistant to decomposition at higher temperatures than other membranes.
Our Technology (657 words)
Nafion is not only highly resistant to chemical attack, it also exhibits highly selective absorption and transfer of compounds.
In addition to the Nafion tubing, most Perma Pure dryers and humidifiers include a shell to contain the purge gas as well as fittings for gas connections to the gas stream and purge lines.
When Nafion tubing bundles are used, the epoxy limits the maximum temperature to 120°C. The maximum internal pressure for all dryers is usually limited by the Nafion tubing to 80 psig at 20°C. Recent advances in some specialty dryers have increased this pressure tolerance.
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