Tetrafluoroethylene with

The higher molecular weight petfluoroalkyl iodides ate prepared by telomerization of tetrafluoroethylene with lower molecular weight perfluoroalkyl iodides (46,48). 

Materials of this type have been sold by Du Pont Co. under the Freon E and Krytox trademarks. Perfluorinated materials stmcturaEy similar to those in equation 11 have been prepared by Ausimont by the low temperature irradiation of either hexafluoropropylene or tetrafluoroethylene with oxygen followed by heating and/or irradiation and have been sold as Fomblin Hquids (52). An isomeric polyether, Demnum, prepared by the oligomerization of 2,2,3,3-tetrafluorooxetane followed by fluorination has been commercialized by Daikin (eq. 12). 

Currently, the commercially important methods of preparations of perfluorkiated sulfonic acid derivatives are electrochemical fluotination and sulfur trioxide addition to tetrafluoroethylene with subsequent ring opening. 

Transitions. Samples containing 50 mol % tetrafluoroethylene with ca 92% alternation were quenched in ice water or cooled slowly from the melt to minimise or maximize crystallinity, respectively (19). Internal motions were studied by dynamic mechanical and dielectric measurements, and by nuclear magnetic resonance. The dynamic mechanical behavior showed that the CC relaxation occurs at 110°C in the quenched sample in the slowly cooled sample it is shifted to 135°C. The P relaxation appears near —25°C. The y relaxation at — 120°C in the quenched sample is reduced in peak height in the slowly cooled sample and shifted to a slightly higher temperature. The CC and y relaxations reflect motions in the amorphous regions, whereas the P relaxation occurs in the crystalline regions. The y relaxation at — 120°C in dynamic mechanical measurements at 1 H2 appears at —35°C in dielectric measurements at 10 H2. The temperature of the CC relaxation varies from 145°C at 100 H2 to 170°C at 10 H2. In the mechanical measurement, it is 110°C. There is no evidence for relaxation in the dielectric data. 

Another direct route is reaction of tetrafluoroethylene with gaseous sulfur in a hot tube (53). The main product is thiocarbonyl fluoride. Lesser amounts of trifluorothioacetyl fluoride and bis(trifluoromethyl)disulfide are also formed. 

Fluoroatcohols. A group of fluorine contg alcohols are available commercially having the general formula H(CFa.GF2)nCH20H, in which n = 1 to 5 They include ales contg C3, C, C7, C9 Ctl, Density of Liquids 1.48-1.66, nD 1.318-1.320 (lowest of all known org compds). Derived by. free radical telomerization of tetrafluoroethylene with methanol. Used as solvents and in org synthesis... 

The amorphous transition at 127° C is depressed to lower temperatures in copolymers of tetrafluoroethylene with up to 14 mole per cent hexa-fluoropropylene (McCrum, 1959b). For this reason it is attributed to longer sequences of CF2 groups. 

Polymerization of tetrafluoroethylene with dibasic acid peroxide catalysts. U. S. Patent 2,534,058 (Dec. 12, 1950). 

In contrast to the telomerisation of tetrafluoroethylene with perfluoroalkyl iodides (RFI), the addition of these telogens to this olefin has not been quite investigated. This may be explained by the fact that the RF(CF2CFCl)nI telomers produced are more efficient telogens than the starting RFI transfer agents as it can be seen in the previous section. Table 13 sums up the results of the literature. 

One of the technically and commercially most important cation-exchange membranes developed in recent years is based on perfluorocarbon polymers. Membranes of this type have extreme chemical and thermal stability and they are the key component in the chlorine-alkaline electrolysis as well as in most of today s fuel cells. They are prepared by copolymerization of tetrafluoroethylene with perfluorovinylether having a carboxylic or sulfonic acid group at the end of a side chain. There are several variations of a general basic structure commercially available today [11]. The various preparation techniques are described in detail in the patent literature. 

The currently available commercial grades Teflon AF 1600 and Teflon AF 2400 produced by du Pont are copolymers of PDD and tetrafluoroethylene with respective glass transition temperatures of 160 and 240°C (320 and 464°F).2 They are produced by aqueous copolymerization of PDD and TEE using fluorosurfactant and ammonium persulfate or other metal persulfate initiators.3... 

Concerning the telomerization, Bedford et al. [47] studied the telomerization of tetrafluoroethylene with IC2F4I and I2. The results are listed in the following table ... 

The only pathway for obtaining a perfectly linear chain as Lichtenberger [133] showed, concerns the telomerization of tetrafluoroethylene with perfluoroalkyl iodides such as C2F5I ... 

Radiation-induced grafting29 was used for the preparation of low-cost polyelectrolyte membranes needed for fuel-cells30. Guzman-Garcia and coworkers29 studied the grafting of poly(styrenesulphonic acid)on polystyrene on a copolymer of poly(tetrafluoroethylene) with polystyrene, and with a copolymer of poly(tetrafluoroethylene) with poly(perfluoropropylene). 

The sole representative in the trithiolane series containing halogen substituents in the ring is tetrafluoro-l,2,3-trithiolane (35). It is found in 10% yield associated with the major product tetrafluoro-l,2,3,4-tetrathiane (204) by reaction of tetrafluoroethylene with the vapors of boiling sulfur at atmospheric pressure (62JOC3995). The compound is rather unstable and rapidly polymerized as described in Section 4.33.3.1.4. 

As with the higher impact resistance achievable with polystyrene when styrene is copolymerized with a rubber, the melt-forming temperatures of PTFE resin may be conveniently lowered by copolymerization of tetrafluoroethylene with low ratios of perfluoropropyl vinyl ether (boiling point, 36°C). The polymerization may be conducted in either an aqueous medium or in an organic solvent (Eq. 23.8). 

The iridium complexes [196], formed by the reaction of tetrafluoroethylene with the appropriate re-allyliridium complex, each show four... 

Starting materials for the synthesis of all perfluoroalkyl iodonium reagents are the perfluoroalkyl iodides, which themselves play a central role as building blocks in fluoroorganic chemistry. The iodides are available either by pyrolysis of the silver salts of perfluoroalkyl carboxylic acids in the presence on iodine [14] or - on a more technical scale - by iodofluorination of tetrafluoroethylene [15] with the iodine-IFp system [16] and subsequent radical telomerization of tetrafluoroethylene with the resulting intermediate perfluoroalkyl iodides [17] (Scheme 2.143). 

Scheme 2.187 Different pathways for reaction of tetrafluoroethylene with nucleophiles.

The reactions of primary phosphines and the corresponding alkyl phosphides with a/ff-unsaturated ketones (25) have been discussed in some detail. " Tetrafluoroethylene with an excess of dimethylphosphine in the gas phase gives (26) by a reaction which is thought to be initiated by the bimolecular abstraction of a hydrogen atom from dimethylphosphine by tetrafluoro-ethylene. Tetrafluoroethylene also reacts with tetramethyldiphosphine by a radical process to give l,2-bis(dimethylphosphino)tetrafluoroethane (27). ... 

A similar behavior has also been observed in membranes obtained by copolymerization. Many recent perfluorinated sulfonated membranes have been obtained by copolymerization of tetrafluoroethylene with a sulfonyl fluoride vinyl ether. This high molecular weight polymer has the following formula ... 

The Nafion resin is a copolymer of tetrafluoroethylene with perfluorosulfonyl-ethoxypropylvinyl ether, which is converted from sulfonylfluoride to sulfonic acid form ... 

The perfluorinated structure imparts stability against chlorine and strong caustic soda at high temperatures, copolymerization of tetrafluoroethylene with molecules such as perfluoro-5-butyrolactone and hexafluoropropylene oxide as ... 

Polytetrafluoroethylene is a completely fluorinated polymer manufactured by free-radical polymerization of tetrafluoroethylene. With a linear molecular structure of repeating -CF2—CF2- units, PTFE is a crystalline polymer with a melting point of 326.7°C. Its specific gravity is 2.13—2.19. Polytetrafluoroethylene has exceptional resistance to chemicals. Its dielectric constant (2.1) and loss factor are low and stable across a wide range of temperature. It has useful mechanical properties from myogenic temperatures to 260°C. In the United States, PTFE is sold as Halon, Algoflon, Teflon, Fluon, Hostaflon, and Polyflon. ... 

In the previous section it was suggested that the parent polymer structure considerably influence the physical properties of the derived polysulfonates, imparting to them some of the mechanical and thermal properties of the precursors. This trend is particularly evident in the case of the perfluorinated hydrocarbon polymers. Polymers of this kind, such as e.g., poly(tetrafluoroethylene) (PTFE) are exceptional in their inertness to offensive environment, solvent resistance and high-temperature stability. These considerations led in the sixties to the development of unique sulfonic-acid derivatives of fluorocarbon copolymers by the DuPont Company. While several compositions were disclosed in the patent literature51, the preferred composition, which is the basis for the commercial Nafion ion-exchange membrane, is a copolymer of tetrafluoroethylene with a perfluorinated vinyl ether/sulfonyl fluoride52 ... 

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