Fluorinated polymeric ethers

Alkali metal fluorides are, in general, not much used for the ring-opening fluorination of epoxides. However, the oligomerization of trifluoro(trifluoromethyl)oxirane induced by cesium fluoride is of some importance for the preparation of fluorinated polymeric ethers 1. ... 

Scheme 4. Homogeneous polymerization of fluorinated vinyl ethers in supercritical C02 [78]...

Vinyl ethers constitute a third class of monomers which have been cationically polymerized in C02. While fluorinated vinyl ether monomers such as those described in Sect. 2.1.2 can be polymerized homogeneously in C02 because of the high solubility of the resulting amorphous fluoropolymers, the polymerization of hydrocarbon vinyl ethers in C02 results in the formation of C02-insoluble polymers which precipitate from the reaction medium. The work in this area reported to date in the literature includes precipitation polymerizations and does not yet include the use of stabilizing moieties such as those described in the earlier sections on dispersion and emulsion polymerizations (Sect. 3). 

Aten, R.M., Melt-fabricable tetrafluoroethylene/fluorinated vinyl ether copolymer prepared by suspension polymerization, U.S. Patent 7,247,690 (July 24, 2007) to E.L du Pont de Nemours and Co. 

Vinyl ethers are another class of monomers which have been successfully polymerized in CO2. As described earlier, fluorinated vinyl ether monomers... 

Shim et al., reported preparation of several novel mono- and di-propenyl ethers by condensation of perfluoroalkyl alcohol with allyl bromide followed by the ruthenium-catalyzed isomerization of the corresponding allyl ethers. These fluorinated propenyl ethers undergo rapid photoinitiated cationic polymerization with the aid of triaryl-sulfonium salt bearing a long alkoxy... 

Many perfluoroaUphatic ethers and tertiary amines have been prepared by electrochemical fluorination (1 6), direct fluorination using elemental fluorine (7—9), or, in a few cases, by fluorination using cobalt trifluoride (10). Examples of lower molecular weight materials are shown in Table 1. In addition to these, there are three commercial classes of perfluoropolyethers prepared by anionic polymerization of hexafluoropropene oxide [428-59-1] (11,12), photooxidation of hexafluoropropene [116-15-4] or tetrafluoroethene [116-14-3] (13,14), or by anionic ring-opening polymeriza tion of tetrafluorooxetane [765-63-9] followed by direct fluorination (15). 

Numerous avenues to produce these materials have been explored (128—138). The synthesis of two new fluorinated bicycHc monomers and the use of these monomers to prepare fluorinated epoxies with improved physical properties and a reduced surface energy have been reported (139,140). The monomers have been polymerized with the diglycidyl ether of bisphenol A, and the thermal and mechanical properties of the resin have been characterized. The resulting polymer was stable up to 380°C (10% weight loss by tga). 

It is interesting to note that all the new aromatic systems, as described, undergo displacement polymerizations in DMAC solvent by the K2CO3 method, except perfluoroalkylene [10] and amide activated polymerization [9], which were performed in NMP solvent. The displacement polymerization in DMAC solvent was carried out at 155-164°C. poly(aryl ether ketones) require less reaction time (3-6 h) than other aromatic systems for synthesis of polyethers [15]. Synthesis of the fluorinated polyether as reported by Irvin et al. [16] was carried out at room temperature for 16 h (Mw = 75,000), whereas the same polymer by Mercer et al. [17] was synthesized at 120°C for 17 h (Mw = 78,970). 

Peduoropolyethers, which constitute special class of fluoropolymer, are useful as lubricants,1 elastomers,2 and heat-transfer fluids under demanding conditions. Several commerical products are available, which are generally prepared by ring-opening polymerization of hexafluoropropylene oxide or by the random copolymerization oftetrafluoroethylene and hexafluoropropylene with oxygen under ultraviolet irradiation.3 Direct fluorination of hydrocarbon ethers has been reported4 but must be done very slowly under carefully controlled... 

The polymerization occurs by ionic addition of OH groups to trifluorovinyl ethers although additions of nucleophiles to fluorinated olefins are well known, few examples of additions to trifluorovinyl ethers have been reported15 and no polymerizations by this method have been described. ... 

Fluorinated polymers, especially polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) and perfluorinated alkyl vinyl ethers (PFAVE) as well as other fluorine-containing polymers are well known as materials with unique inertness. However, fluorinated polymers with functional groups are of much more interest because they combine the merits of pefluorinated materials and functional polymers (the terms functional monomer/ polymer will be used in this chapter to mean monomer/polymer containing functional groups, respectively). Such materials can be used, e.g., as ion exchange membranes for chlorine-alkali and fuel cells, gas separation membranes, solid polymeric superacid catalysts and polymeric reagents for various organic reactions, and chemical sensors. Of course, fully fluorinated materials are exceptionally inert, but at the same time are the most complicated to produce. 

Thus, precursors such as hydrocarbon ethers, amines, carbonyl compounds which are readily protonated tend to be more amenable to ECF than, say, hydrocarbons or halocarbons whose solubilities and conductivities are low. A number of techniques have been developed in the past decade, however, to overcome such problems (see Sect. 4.2). Similarly, advances in methodology of ECF now allow the fluorination of gaseous, liquid, solid, and even polymeric materials [72-77]. 

Diazotization in the presence of boron trifluoride enables diazonium tetrafluoroborates to be isolated from the reaction mixture and purified. Subsequent controlled decomposition produces the required fluoroaromatic. Although explosion hazards and the toxicity of the isolated salts are significant concerns with this process, known as the Balz-Schiemann process, 4,4 -di-fluorobenzophenone (BDF. 6) has been prepared by this route as a monomer for the production of the engineering plastic poly(ether ether ketone) , or PEEK , by condensation with 1,4-dihydroxybenzene in the presence of potassium carbonate. BDF 6 is superior to its chlorine analog because in aromatic systems the nucleophilic displacement of fluorine is more facile than that of chlorine, leading to a shorter polymerization time and a better quality product containing less degradation impurities. 

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