Fluorocarbon polymer chemistry

Florin RE (1972) Radiation Chemistry of Fluorocarbon Polymers. In WaU LA (ed) Fluoropolymers. WUey, New York, p 317... 

Florin, R.E. (1972) Radiation chemistry of fluorocarbon polymers. Fluoropolymers, 11, 317-331. 

This reaction mechanism has already been reported.23,24 The mechanism is actually quite significant for the economics and efficiency of the preparative chemistry. The fact that an S 2 mechanism is not in effect here means that only a slight stoichiometric excess of the fluorocarbon reagent is required for good yields of the intermediate products. Also, the action of an S 2 mechanism would make the desired product itself susceptible to a second nucleophilic attack on the terminal -CF2Br, resulting primarily in the production of polymer from this reaction instead of the observed product. 

A new method for the syntheses of fluorocarbon polyarylate polymers has been demonstrated. The chemistry utilizes the [2jt+2rr] cyclodimerization of fluorinated olefins and generates polymers of novel composition. The first generation of polymers prepared by this method are polyarylate homopolymers. Theremoplastic polymers of high molecular weight can be achieved via neat or solution polymerization. One example of a thermoset polymer prepared by this method has a high Tg, low dielectric constant and dissipation factor, low moisture... 

Although both neutral and ionic species have been monitored by in situ mass spectrometric analysis of C2p plasmas, this discussion will be largely restricted to the neutral chemistry since in general the amount of polymer deposited relative to the amount of monomer fed into this system is too large for ionic spcies to be solely responsible for the process . This is not, however, to say that the ionic species do not play any role in the polymerization process and the importance of the ions in the plasma polymerization of fluorocarbons will become apparent. 

The other major springboard for the fluorocarbon chemical industry was the "Manhattan Project to develop the atomic bomb. This required the large-scale production of highly corrosive elemental fluorine and uranium(VI) fluoride for the separation of the radioactive 235U isotope. Oils capable of resisting these materials were needed to lubricate pumps and compressors, and polymers were needed to provide seals. Peril uorinated alkanes and polymers such as PTFE and poly(chlorotrifluoroethylene) (PCTFE) proved to have the appropriate properties so practical processes had to be developed for production in the quantities required. In 1947 much of this work was declassified and was published in an extensive series of papers3 which described the fundamental chemistry on which the commercial development of various fluoro-organic products, especially fine chemicals, was subsequently based. 

Copolymers of VDF and HFP, completely amorphous polymers, are obtained when the amount of HFP is higher than 19 to 20% on the molar base.6 The elastomeric region of terpolymers based on VDF/HFP/TFE is defined by the monomer ratios. Commercially, VDF-based fluorocarbon elastomers have been, and still are, the most successful among fluoroelastomers.7 The chemistry involved in the preparation of fluorocarbon elastomers is discussed in some detail in Chapter 2. 

Fluorocarbon compounds were radiolyzed to establish the existence and assess the role of valence tautomers in radiation chemistry. Dewar-octafluorotoluene and -decafluo-roxylene have been isolated and identified as products of the photolysis and radiolysis of their respective aromatic parent in condensed phase. Dewar hexafluorobenzene was irradiated to 10 Mrad doses and found to revert to its KekulS isomer with a G-value of 10, to polymerize with G 20, and, in addition, to give rise to a new isomer. The concept of an energy sink is introduced whereby part of the energy absorbed by an aromatic system is stored in the form of interconvertible valence isomers which react further to yield polymers or decay to the ground state. 

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