Poly-perfluorocarbons

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. 

Using a similar philosophy to the perfluorocarbon liquid approach, Piletsky carried out suspension polymerisations in silicone oil. This liquid is also immiscible with some organic liquids, although the range of immiscible combinations is much smaller than for perfluorocarbons. Beads were successfully produced containing imprints of ATP and poly-A in an EDMA/A,A-diethyl-2-aminoethylmethacrylate system with DMF as solvent and an excess of silicone oil as dispersant [21]. 

Washington, C. King, S.M. Effect of electrolytes and temperature on the structure of a poly(ethylene oxide) poly(propylene oxide) poly(ethylene oxide) block copolymer adsorbed to a perfluorocarbon emulsion. Langmuir 1997, 13, 4545-4550. 

Solid perfluorocarbon surfaces also have extremely low surface energies Thus, poly(tetrafluoroethylene) (PTFE, Teflon) has a y value of 18.5 dyn cm which is the reason for the anti-stick and low-friction properties used for frying pans and other applications. That this effect is directly related to the fluorine content becomes obvious on comparison of the surface energies of poly(difluoro-ethylene) (25 dyn cm ), poly(fluoroethylene) (28 dyn cm ), and polyethylene (31 dyn cm Y If only one fluorine atom in PTFE is replaced by more polarizable chlorine, the surface energy of the resulting poly(chlorotrifluoroethylene) jumps to 31 dyn cm , the same value as for polyethylene [8]. 

Fe(CN)6]3-.332 Another case to obtain quinone and hydroquinone by electrochemical oxidation of benzene with a high current efficiency, an anode modified by a bipolar ion exchange membrane, composed of a protonated poly-4-vinylpyridine layer and a perfluorocarbon sulfonic acid layer, is used. [Fe(CN)6]3 is incorporated in the inner layer (protonated poly-4-vinylpyridine) and is not contained in the solution. Release of [Fe(CN)6]3 from the inner layer is prevented by the outer layer. As a result, redox catalysts, i.e., Cr6+/Cr3+, or [Fe(CN)6]4-/ [Fe(CN)6]3 incorporated in the bipolar ion exchange membrane on the electrode surface accomplish catalysis more efficiently than if they were dissolved in the electrolyte solution.333... 

Phosphonated polymers have been proposed for fuel cells with the expectation of being thermally more stable and better retaining water than sulfonic groups [210, 211]. Phosphonated poly(phenylene oxide) [212], poly(4-phenoxy-benzoyl-l,4-phenylene) [213] and polysulfones [214, 215] have been reported. Phosphonated fluoromonomers were polymerized [164]. Characterization of phosphonated films in terms of their proton conductivity has been reported for some of the phosphonated polymers polyphosphazene [216], trifluoropolysty-rene [217], poly(4-phenoxybenzoyl-l,4-phenylene) [218]. Relatively low conductivity values were reported for most of the polymers prepared up to now. The values for polyphosphazene [216] and for perfluorocarbon polymers [219] were quite encouraging. Phosphonated poly(phenylene oxide) [211] was evaluated in fuel cell-tests. 

T. C. Merkel, V. Bondar, K. Nagai, B. D. Freeman, Sorption and transport of hydrocarbon and perfluorocarbon gases in poly(l-trimethylsilyl-l-propyne), J. Polym. ScL, Part B Polym. Phys., 38, 273-296 (2000). 

Scheme 13.3 Phosphonated fluorinated pol miers (a) poly(2,3,5,6-tetrafluoro-4-vinylphenylphosphonic acid), (b) phosphonated perfluorocarbon polymer,(c) phosphonated fluorinated copol)Tner, (d) phosphonated fluorinated poly(aiyl ether). ...

Common liquid phases belong to one or other of the categories (1) hydrocarbon and perfluorocarbon liquids, (2) ether and ester liquids, (3) ionic liquids, and (4) poly(siloxanes). Of these, poly(siloxanes) and poly(ethylene glycol) stationary phases dominate the practice of WCOT columns, because unlike most liquids they can be immobilized by simple chemical reactions to prepare films of different thickness that are stable to temperature variation and solvent rinsing while retaining favorable kinetic properties. 

Since the discovery of conductivity in ice in the last century, proton transport in solids has aroused great scientific interest. Synthesis of Nafion Perfluorocarbon sulphonic acid poly-... 

At that time, a mixed electrolyte membrane made of fluorocarbon and poly(styrene sulfonic acid) was used. Later, as development continued for aerospace and military purposes, in 1972, the perfluorocarbon membrane Nafion was introduced and it drastically improved chemical resistance. 

Very early hydrocarbon-based membranes tested as electrolytes in PEMECs for Gemini space missions, such as sulfonated phenol-formaldehyde resins, sulfonated poly(styrene-divinylbenzene) copolymers, and grafted polystyrene sulfonic acid membranes, were chemically weak, and therefore PEMFCs using these membranes showed poor performance and had only lifetimes of several hundred hours (LaConti et al. 2003). Nafion , a PESA membrane, was developed in the mid-1960s by DuPont (LaConti et al. 2003). It is based on an aliphatic perfluorocarbon sulfonic acid, and exhibited excellent physical properties and oxidative stability in both wet and dry states. A PEMEC stack using Nafion 120 (250- tm thickness, equivalent weight = 1,200) achieved continuous operation for 60,000 h at 43-82°C (LaConti et al. 2003, 2006). A Nafion -based PEMFC was used for the NASA 30-day Biosatellite space mission (LaConti et al. 2003). 

Schroder [20b] used high-performance liquid chromatography (HPLC)/ mass spectrometric (MS)/MS with a thermospray interface [20c] to detect, identify, and quantify metabolites of Fluowet OTN, a nonionic fluorinated surfactant with the structure R F2,i+iCH2CH2(OCH2CH2)wOH. The biodegradation was limited to the poly(oxyethylene) hydrophile [20b]. The absence of fluoride ions indicated that the perfluorocarbon chain was not degraded. 

---