Perfluorinated materials

Many of the unusual properties of the perfluorinated inert fluids are the result of the extremely low intermolecular interactions. This is manifested in, for example, the very low surface tensions of the perfluorinated materials (on the order of 9-19 mN jm. = dyn/cm) at 25°C which enables these Hquids to wet any surface including polytetrafluoroethene. Their refractive indexes are lower than those of any other organic Hquids, as are theh acoustic velocities. They have isothermal compressibilities almost twice as high as water. Densities range from 1.7 to 1.9 g/cm (l )-... 

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). 

The lowest wettable surface known = 6 dyne/cm) is a monolayer of perfluoro-launc acid on platinum, whose surface is made up of closely packed CF3 groups [20] Fluonnated graphite, (C2FJ and (CF) , also have surface tensions approachmg 6 dyne/cm [21] Perfluorinated materials, however, are not required tor low surface energies only the outermost surface groups must be perfluorinated [20, 22]... 

Completely perfluorinated carboxylic acids have never been deposited with total success as LB films, as it is very difficult to synthesise materials of this nature containing more than 12 carbon atoms. Unfortunately, it is not possible to form stable monolayers at the air/water surface or dip successfully when making use of such short chains. Nakahama et al. [143] claim to have carried out these processes using a subphase containing aluminium ions. However, extensive efforts to reproduce these results which were made in the author s laboratory proved unsuccessful. Naselli et al. [144] studied the partially perfluorinated material... 

From these results, the permeability of oxygen in a Nation film can be obtained as the product of its concentration by its diffusion coefficient in the film DfCf. Figure 1.15 shows the variation of the oxygen permeability with the temperature. Like many perfluorinated materials, the Nation membrane is especially a good solvent of oxygen. 

Kharitonov et al. [59] have shown that direct fluorination of the polyimide Matrimid is possible, hence the resulting membrane should have a nice potential for use in harsh environment. Perfluorinated materials were also studied by Hagg [60] for chlorine gas purification, and were shown to be exceptionally stable in these harsh environments. The selectivity was however too low. In a later publication on chlorine purification [31] it was suggested to use perfluorinated monomers as surface-modifying compounds for pore tailoring of glass membranes for chlorine gas separation. 

Ltd.) and the perfluorinated membranes produced by the Asahi Chemical Industry Company (18). Recently, carboxylate perfluorinated materials have been available from DuPont Company. 

Sorbed Water. Because Nafion is a perfluorinated material, it is straight-forward to observe the NMR signal of water hydro-... 

The important feature of perfluorinated materials for electrochemical application is their excellent or, perhaps, improved, chemical inertness and mechanical integrity in a corrosive and oxidative environment (8, 9). In contrast, the hydrocarbon type material is unstable in this environment, due to the cleavage of the carbon-hydrogen bonds, particularly the a-hydrogen atom where the functional group is attached (9,10) ... 

The thermal stability of perfluorinated material is excellent as evidenced by the higher glass transition temperature over their respective non-fluorinated analogues (11). Accordingly, these perfluorinated materials can be used in electrochemical cells at an elevated temperature for better cell efficiency because of high conductivity and fast kinetics (12) The relatively high cost of the perfluorinated membrane limits its application in many electrochemical cells when cost-effectiveness is a major concern. 

The Nafion membrane has been used as a separator in both the hydrogen-halogen cell (45,50) and in the zinc-bromine cell (38) because Nafion is a highly stable perfluorinated material which is not affected by strong acids and halogen. 

In this chapter, we focus on the effect of fluorine as a substituent in a simple polymeric system, polyacetylene. Polyacetylene, of course, has several potentially practical uses because of its conducting and optoelectronic properties (15) and we are interested in studying how F substitution might influence these properties. Our model systems are butadiene and hexatriene, and we discuss both partially fluorinated and perfluorinated materials. Because we discovered that CF - HC hydrogen bonding is important in these systems, we also present results on the nature of the intramolecular hydrogen bond between the CF and OH groups in alcohols and enols. Related results on intramolecular coordination of alkali metals to C-F bonds in fluoroenolates are briefly described. 

Preparation of Perfluorinated Nitrogen and Nitrogen-Oxygen Containing Heterocycles A wide range of perfluorinated amines was prepared in last 60 years. Electrochemical fluorination is the main method used for the preparation of variety saturated perfluorinated heterocycles. Despite the low yields of perfluorinated materials, the process is reliable and can be used for the preparation of perfluorinated materials. Detailed reports on the use of ECF for the preparation of fluorinated materials can be found in several reviews published in last 40 years Major types of perfluorinated N-... 

The junction between an electronic conductor and a polymeric proton conductor gives a very interesting tool for the study of mass and charge transfer in solids and in solutions. In addition, the perfluorosulphonic proton conductor gives new synthesis routes in organic or electro-organic chemistry. Future developments in this family of proton conductors are to be expected for the preparation of low price perfluorinated materials. 

Fluoropolymers of different types are commercially available as coating resins [96]. Methods to fabricate perfluorinated coatings and films to impart the desirable properties of perfluorocarbons where they are most needed, without the disadvantages of handling and applying bulk perfluorinated materials are described in the literature [97]. 

In the preceding chapter, recent progress on perfluorinated ionomer membranes is reviewed. There is no doubt that the perfluorinated ionomer membranes will dominate in the area of polymer electrolyte fuel cells (PEFCs) for the years to come however, drawbacks peculiar to perfluorinated materials such as high production... 

Nation. Nation is the trade mark (produced by DuPont) of a perfluorinated material composed of carbon-fluorine backbone chains and perfluoro side chains with sulfonic acid ion-exchange groups ... 

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