Fluorocarbons, functionalized, synthesis

In the past decade, C-F bond activation chemistry has progressed from a laboratory curiosity to the verge of becoming a useful synthetic technique in organic chemistry. The most important issue that needs to be addressed is that of selectivity. In addition, extension of work described above to less heavily fluorinated aromatics and to aliphatic fluorocarbons in the absence of tertiary C-F bonds would be desirable. A healthy debate concerning the mechanisms of this reactions has begun and further study may guide the discovery of new catalysts for fluorocarbon functionalization. Fluorocarbons may also serve as sources of carbon in the synthesis of new materials [39, 90]. Under appropriate conditions, fluorocarbons are indeed reactive molecules [91]. 

The high-molecular-weight perfluoropolyethers obtained in the first step have excellent thermal stability (TGA initial decomposition >370°C) and chemical resistance and are true fluorocarbon elastomers that are, in contrast to polytetrafluoroethylene, flexible. Other methods for the synthesis of perfluoropolyethers and functionalized perfluoropolyethers are under development in our laboratories. 

There is considerable promise for the synthesis of useful functionalized fluorocarbon materials using other direct fluorination techniques (46), such as the fluorination of pendant polyesters and polymers containing pendant acyl fluoride units. 

Liquid fluorocarbon was used as continuous phase by Perez-Moral and Mayes [19] as well. They proposed a new method for rapid synthesis of MIP beads, in that they prepared 36 polymers imprinted for propranolol and morphine with different amounts of EDMA as a cross-linker and different functional monomers (MAA, acrylic acid, hydroxyethyl methacrylate, 4-vinylpyridine) directly in SPE cartridges. The properties of MIP microspheres prepared by this method were very similar in terms of size, morphology and extent of rebinding to microspheres prepared by conventional suspension polymerisation in perfluorocarbons as well as to bulk polymers prepared in the same solvent. The most notable advantages of this method are no waste production (no transfer of beads during washing steps) and possible direct use for a variety of screening, evaluation and optimisation experiments. 

Perhaps the most exciting recent advances in the organometallic chemistry of fluorocarbons have been the contemporaneous and complementary discoveries of examples of catalytic activation and functionalization of perfluorocarbons in laboratories led by Crabtree and Richmond [23]. Kiplinger and Richmond [64] showed that Group 4 metallocenes function as catalysts in the synthesis of per-fluoronapthalene from perfluorodecalin using activated Mg or Al as the terminal reductant. Low valent zirconocene or titanocene species were postulated as intermediates in the catalytic cycle and control experiments showed the central role played by the metallocene in mediating electron transfer in these systems. Turnover numbers up to 12 (net removal of 120 fluorines/metallocene) were noted [64]. 

Esters, polyglycols, fluorocarbons and other fluid families with valuable tribological properties are not available in mineral oils. Functionalization of synthetic fluids expands the opportunities for performance enhancement and can bridge the gap between base stocks and additives. There is an equally wide variety of chemistry used in additive synthesis. 

Acrylic pol niiers of linear and of cross-linked varieties are important classes of materials, and the fluorocarbon polymers are likewise important for substantially different reasons. The broad resistance of fluorocarbons to physical and chemical attack suggests that acrylics could be enhanced by the introduction into the molecules of substantial amounts of fluorine, provided such an addition did not compromise the characteristic acrylic properties. Fluorocarbons also possess a range of unusual surface chemical properties which could make for greater versatility in the acrylics if imparted thereto. For example, a fluoroacrylic resin in the liquid, precured state is expected to be of low surface tension and excellent wetting capability for difficult-to-wet fillers, such as powdered Teflon, whereas the cured fluoracrylic can be expected to be relatively non-wetting and non-absorptive of most liquid systems, particularly those that are water based. In order to attempt such an enhancement of acrylic properties, the synthesis of a series of fluorine-bearing acrylics of various functionalities was undertaken. 

The problem of introducing substantial quantities of stable fluorocarbon into resins without undue compromise of the strength properties has been previously solved for epoxy systems (1-3). The intermediates for these epoxies were a series of fluoro tertiary alcohols with aromatic nuclei surrounded by perfluorinated aliphatic groups and bearing hydroxyl functionalities derived from hexafluoro-acetone. The present synthesis problem entailed the esterification of these intermediates to yield acrylic esters. 

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