Fluorinert fluorinated solvent

Our typical preparation method for these perfluorodioxolane monomers and polymers is shown in Scheme 16.5 [13-18]. Commercially available methyl pyruvate and diols are used as the starting materials. The condensation product is then directly fluorinated in a fluorinated solvent such as Fluorinert FC-75 by the F2/N2 mixture. After flushing the system using nitrogen gas for 1 hour, fluorine gas diluted to 20% with nitrogen is blown into the reaction mixture at a flow rate of 240 L/h. The reaction is carried out at a temperature of around 25°C for over 20 hours. After the reaction is over, the mixture is neutralized with aqueous potassium hydroxide solution. The... 

The copolymers obtained are soluble in fluorinated solvents such as HFB and Fluorinert solvents. of the copolymers is in the range of 84-145 C and are thermally stable (T 320-370°C). The copolymer films are flexible and clear with a low refractive index (1.332-1.375 at 633 nm). 

One of the most efficient and simplest routes for the fabrication of these perfluorodioxolane monomers and polymers is shown in Scheme 4.3 [26-30]. Commercially available methyl pyruvate and diols are used as the starting materials. The condensation product is then directly fluorinated in a fluorinated solvent such as Fluorinert FC-75 (3M) with a F2/N2 mixture. After flushing the system with nitrogen gas for 1 h, fluorine gas diluted to 20% with nitrogen is blown into the reaction mixture at a flow rate of 2401/h. The reaction is carried out at approximately 25 C for over 20 h. After the reaction is complete, the mixture is neutralized with aqueous potassium hydroxide. The crude monomer is isolated upon decarboxylation of the potassium salt and then purified by fractional distillation. The fluorination process is the key step in the synthesis. The yield is as high as 75% with careful control of the fluorination temperature, and it depends on the structure of the hydrocarbon precursor. Recently, over 90% yield of the fluorination of similar compounds has been reported [31]. The polymerization of these monomers is generally carried out in bulk at 60 - 80 °C for 24-35 h using perfluorodibenzoyl peroxide as the initiator [32]. The conversion yields are 70-80%, and the polymers obtained are colorless and transparent. 

In order to minimize the degradation of macromolecules, the choice of solvent is not a trivial matter. Hydrogen-containing solvents are obviously not suitable, but even halogenated ones such as CFC13 or CC12FCF2C1, usually stable to fluorine, can react violently with this element when irradiated at temperatures near 0°C. We chose two perfluorinated solvents that have been proven safe and suitable for radical fluorination perfluoro-2-(butyl)-tetrahydro-duran (FC-75 Fluorinert from 3M) and hexafluoropropylene oxide (HFPO) oligomers known as Krytox +... 

The Stevens group [20] performed the reaction under microreaction conditions using the previously mentioned CYTOS College System [18]. The main problem with this setup is the formation of crystals (as the final products are crystalline) that leads to clogging of the system. This was circumvented by injection of a fluorinated inert solvent (Fluorinert FC-70) after the micromixing unit and before the RTU, which prevented the clogging and allowed the authors to collect the desired compounds easily by phase separation. 

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