Perfluoroalkoxy groups

Addition of Fluorine and a Perfluoroalkoxy Group with Perfluoroalkyl Hypofluorites... 

Perfluoroalkoxy groups and, especially, the trifluoromethoxy group, are commonly used as structural elements in pharmaceuticals (Section 4.5) and organic materials (Section 4.4). Aromatic and aliphatic perfluoroalkoxy groups are conveniently accessible via fluorodesulfuration chemistry (see also Section 2.1.5.4). Nevertheless, the technically important trifluoromethoxy arenes, in particular, are produced on a larger scale by a different method, based on chlorine-fluorine exchange with hydrofluoric acid [17] (Scheme 2.172). 

Perfluoro rubbers of the poly- methylene type having all substituent groups on the polymer chain either fluoro, perfluoroalkyl, or perfluoroalkoxy groups Fluoroelastomer FFKM... 

Fluoro rubber of the polymethylene type having substituent fluoro and perfluoroalkyl or perfluoroalkoxy groups on the polymer chain Fluoroelastomer FKM... 

Also, FEPM is a class of fluoroelastomers prepared from monomeric units containing one or more alkyl, perfluoroalkyl, or perfluoroalkoxy groups, with a reactive pendant group. This class of fluoroelastomers does not contain vinylidene fluoride monomer units. 

FFKM is a perfluorinated polymethylene rubber with fluoro, perfluoroalkyl, and/or perfluoroalkoxy groups on the polymer chain, likely with a small fraction of perfluorinated monomer units containing functionality to enable vulcanization. 

The structure of LiN(Rf0S02)2 is similar to that of lithium bis(perfluoroalkyl sulfonyl)imide, the difference being the perfluoroalkoxy group RfO instead of the perfluoroalkyl group Rf. It is relatively easy to prepare. First, a dihalo-sulfonamide reacts with perfluoroalkyl alcohol (RfOH) to prepare bis(per-fluoroalkoxysulfonyl)imide (HN(S020Rf)2), which is then reacted with lithium carbonate or lithium hydroxide in solution to obtain lithium... 

The preparation of silicones and polysiloxanes containing perfluoroalkoxy groups has been described in the patent literature, e.g. 

The nitro groups in TNB were replaced with alkoxy [7, 8] or perfluoroalkoxy [9-15] groupings using aromatic nucleophilic nitrodisplacement reaction [16-19] in accordance with Scheme 4.4. Monosubstituted dinitro compounds thus obtained were reduced to the corresponding diamines [7, 8, 11-15] in accordance with Scheme 4.5. The simplest of the target diamines, 3,5-diaminoanisole [7, 20, 21], was prepared in accordance with Scheme 4.6. 

The need for highly fluorinated thermoplastic polymers that, unlike PTFE, could be fabricated by conventional melt-processing methods led to the development of a group of resins that are copolymers of tetrafluoroethylene (TFE) with other perfluo-rinated monomers. Commercially, the copolymer of TFE and hexafluoropropylene (HEP) is commonly known as fluorinated ethylene propylene (FEP). Copolymerization of TEE with perfluoropropylvinyl ether (PPVE) leads to perfluoroalkoxy (PEA) resins, and copolymerization of TFE with perfluoromethylvinyl ether (PMVE) produces methylfluoroalkoxy (MEA) resins. 

Perfluoroalkoxy (PFA) Polymer - Rf is a perfluorinated alkyl group containing one or more carbon atoms, typically a maximum of four carbon atoms. 

The high-polymeric linear phosphazenes are potentially useful materials as far as physical and mechanical properties are concerned, but they have been generally useless because of chemical (especially hydrolytic) instability. Recently, use of perfluoroalkoxy and other side groups has given promise that useful polymers may yet be developed.47 b> 51... 

Making a more dramatic change in the side group than that done in making FEP, chemists put a perfluoroalkoxy (PFA) group on the polymer chain. This group is signified as —O—Rf, where Rf can be any number of totally fluorinated carbons. The most common comonomer is perfluoropropyl (—O—CF2—CF2—CF3). However, other comonomers are shown in Table 9.3. 

FEP contains CFj side groups due to copolymerisation with 10-12% hexafluoropropylene. The side groups tend to lock together and improve mechanical properties at processable molecular weights. FEP can be processed by extrusion, and its creep performance is better than that of PTFE. However steric stress due to the bulky side group reduces the CUT from 260 to 200 °C. PFA introduces a perfluoroalkoxy side chain - typically OC3F7. PFA can be injection moulded. Both PFA and FEP have PTFE-like chemical resistance and... 

Read et al. synthesized surface-active derivatives of 1,2,3-triazole 49,50 containing at the nitrogen atom perfluoroalkyl (lipophilic) substituents, and at the carbon atom perfluoroalkoxy or alkoxy (hydrophilic) groups. It is significant that the surfactant properties of these compounds can be purposefully regulated varying the length of the fluoroalkyl chain [49, 50],... 

Polytetrafluoroethylene (PTFE) and its copolymers fluoroethylenepropylene (FEP), perfluoroalkoxy (PFA), and amorphous PTFE, a perfluorinated dioxole (Teflon AF), are the best electret materials for storing negative charges due to the large electronegativity of the F atom and the highly symmetrical CF2 group with its... 

For example, perfluoroalkoxy polymer (PEA) is a copolymer of IFE and perfluoro kylvinylether that contains oxygen. R is a perfluoroalkyl group of C, toC. ... 

End groups are stabilized by treating the PFA with methanol, anmionia, amines, and elemental fluorine that produces CFj end groups [73-77]. The polymer is recovered, dried, and melt-extruded into cubes for melt fabrications processes. Perfluoroalkoxy is also available in bead (as-polymerized), dispersion and fine powders forms. 

Table 5.33. Number of End Groups of Perfluoroalkoxy Polymers (See Table 5.28 for Process Conditions) ...

EKM Polymethylene fluoro rubber from vinylidene fluoride and a comonomer fluoro, alkyl, perfluoroalkyl, or perfluoroalkoxy substituent groups with... 

On the basis of IR results, the hydroxyl radicals attack the polystyrene via addition to the phenyl groups (Weir 1978). The results were verified by FTIR analysis of PFA- -PSSA (where PFA is perfluoroalkoxy) after fuel cell durability tests (Nasef and Saidi 2(X)2). This pathway is also supported by ESR experiments on model compounds (Hubner and Roduner 1999). 

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