Oxidation perfluoropolyether

Perfluoropolyethers emerged on the market ia the early 1970s however, for the next 15 years there were only two basic stmctures known. The first perfluoropolyether was the homopolymer of hexafluoropropylene oxide produced by Du Pont having the stmcture... 

Two of the perfluoropolyether fluid stmctures yet to be commercialized are interesting. The first stmcture is a strictly alternating copolymer of ethylene oxide and methylene oxide, which has the longest Hquid range of any molecule containing carbon (40). The second stmcture is the perfluoromethylene oxide polyether which has low temperature Hquid properties down to —120° C ... 

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). 

Information on the production levels of the perfluoroethers and perfluorotertiary amines is not disclosed, but the products are available commercially and are marketed, for instance, as part of the Fluorinert Electronic Liquids family by 3M Co. (17). These Hquids have boiling points of 30—215°C with molecular weights of about 300—800. They range in price from 26—88/kg. Perfluoropropene oxide polyethers are marketed by Du Pont with the trade name Krytox (29). The linear perfluoropropene oxide polyethers are marketed by Daikin under the trade name Demnum (28). The perfluoropolyethers derived from photooxidation are marketed by Montefluos under the trade name of Fomblin (30). These three classes of polyethers are priced from about 100—150/kg. 

Perfluoropolyethers emerged on the market in the early 1970s. The first perfluoropolyether was the homopolymer of hexafluoropropylene oxide produced by DuPont, which has the structure [—CF2CF(CF3)0—] and this new lubricant material was called Krytox.31,32 Krytox was and is used in most of the vacuum pumps and diffusion oil pumps for the microelectronics industry because it does not produce any hydrocarbon or fluorocarbon vapor contamination. It also has important applications in the lubrication of computer tapes and in other data processing as well as military and space applications. 

The Lagow group first entered the perfluoropolyethers field in 1977, by reacting fluorine with inexpensive hydrocarbon polyethers to prepare perfluoropolyethers. In the simplest case (Figure 14.3) poly (ethylene oxide) is converted to perfluoroethylene oxide polymer, a simple reaction chemistry that we first reported in the literature.27 As will be seen later, this direct fluorination technology as well as many new patents from Exfluor Research Corporation have been non-exclusively licensed to the 3M Corporation by the Lagow research group.3 "39... 

Subsequently, we were able to make perfluorinated analogues ofKrytox from the hydrocarbon polypropylene oxide)40 (Figure 14.4). In 1985, we published three interesting perfluoropolyethers. First we copolymerized hexafluoroacetone with ethylene oxide, propylene oxide, and trimethylene oxide. Subsequent fluorination yielded the new perfluoropolyethers (Figure 14.5). 

A promising and extremely interesting new area of research is the synthesis of perfluoropolyethers by the reaction of elemental fluorine with hydrocarbon polyethers (34, 35). An extensive recent research program at the University of Texas at Austin has succeeded in establishing the generality of this approach. In the initial study, polyethylene oxide was reacted with elemental fluorine under... 

Synthetic methods have limited the preparation of saturated perfluoropolyethers. The most successful perfluoropolyether synthetic chemistry has been DuPont s anionic polymerization of perfluoroepoxides, particularly hexafluoro-propylene oxide and tetrafluoroethylene oxide (39). Their synthetic procedure is a three-step scheme for saturated perfluoropolyether production involving oxidation of perfluoroolefins to perfluoroepoxides, anionic polymerization to acyl fluoride terminated perfluoropolyethers, and conversion of acyl fluoride end groups to unreactive end groups by decarboxylation reactions or chaincoupling photolytic decarboxylate reactions. 

The use of sc C02 instead of toluene as a solvent leads to some rate enhancement in these two systems, although it is clear that this activity is still not practical for most nonpolar, nonvolatile substrates. Significant improvements to the biphasic water/supercritical C02 system were accomplished by forming H20/C02 emulsions using newly developed surfactants (Jacobson et al., 1999). Three different surfactants were used that form water in C02 (w/c) or C02 in water (c/w) emulsions (1) anionic surfactant perfluoropolyether ammonium carboxylate, (2) cationic Lodyne 106A, and (3) nonionic poly(butylene oxide)-h-poly(ethylene oxide). The low interfacial tension, y, between water and C02 (17 mNm-1 at pressures above 70 bar), which is significantly lower than water/alkane systems (30-60 mNm-1),... 

Hexafluoropropylene oxide is an important intermediate in fluoroorganic synthesis. It is useful in the production of surfactants, perfluoropolyether oils, solvents, perfluorinated alkylvinyl ethers, and other materials. 

Panza et al. synthesized a C02-philic amphiphile from the coenzyme nicatinamide adenine dinucleotide (MW 664) and a covalently attached perfluoropolyether (MW 2500) (Figure 7B) (73). The fluorofunctional coenzyme (FNAD) was soluble up to 5 mM in CO2 at room temperature and 1400 psi. The C02-soluble FNAD was able to participate in a cyclic oxidation/reduction reaction catalyzed by the enzyme horse liver alcohol dehydrogenase (HLADH) in CO2 at room temperature and 2600 psi. 

The potential of microemulsions for organometaUic-catalyzed hydrogenations in water/scC02 biphasic systems has been assessed using the rhodium-catalyzed hydrogenation of styrene as a common test reaction [Eq. (7)] [31]. The water-soluble Wilkinson complex [RhCl(TPPTS)3] was applied as catalyst precursor together with anionic perfluoropolyether carboxylates, cationic Lodyne A, or nonionic poly-(butene oxide)-b-poly(ethylene oxide) surfactants. The interfacial tension is small in the presence of the supercritical fluid and small amounts of surfactant (0.1-2.0 wt.%) suffice to form stable microemulsions. The droplet diameter of the microemulsions varied between 0.5 and 15 pm and a surface area of up to 10 m was obtained. 

KEX. See Potassium ethyl xanthate Keycide X-10. See Tributyltin oxide Keystone 1104. See Polyaluminum chloride Keystone 1138. See Aluminum chlorohydrate K-FluldK5 K-Fluld K6 K-FluidK7 K-Fluld K8 K-Fluld K9. See Perfluoropolyether KF Polymer C-100a, KF Polymer 0-150(7, KF Polymer 7-85(7, KF Polymer T-850CF KF Polymer T-1000, KF Polymer T-1KX7, KF Polymer T-1200 KF Polymer 7-130(7, KF Polymer 7-1500 KF Polymer 7-200(7, KF Polymer U-1000 KF Polymer W-100(7, KF Polymer W-1400HD. See Polyvinylidene fluoride resin... 

The common surfactants discussed repeatedly here and elsewhere are in general unsuitable for water-supercritical carbon dioxide emulsions of all types (including microemulsions). Selections are made, to start with, on the basis of the water/ carbon dioxide solubility behavior. A surfactant used in some of the initial studies is ammonium carboxylate perfluoropolyether [24,25]. Subsequently, a variety of triblock co-polymers, e.g. poly(propylene oxide-b-ethylene oxide-b-propylene... 

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