Perfluorodibenzoyl peroxide

Initiator perfluorodibenzoyl peroxide, polymerization teinterature 60°C, polymerization time 24 h, yield of polymers 75-90%. 

The polymerization of these monomers is generally carried out in bulk at 60-80°C using perfluorodibenzoyl peroxide or perfluoro-di-fert-butyl peroxide as the initiator [20] for 24-35 hours. The conversions are 70-80% and the polymers obtained are colorless and transparent. The polymers are purified by precipitation fi om their solutions in HFB into chloroform. 

The decomposition of perfluorodibenzoyl peroxide is performed at 60-80°C by a homolysis mechanism resulting in the formation of a pentafluorobenzyl stmctural unit at the polymer end (Scheme 16.6) [19,20]. Thus, poly(perfluoro-2-methylene-1,3-dioxolanes) produced are generally thermally stable and the decomposition temperature (T ) in the air atmosphere is >300°C. 

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. 

The decomposition of perfluorodibenzoyl peroxide occurs at 60—80 C by a homolytic mechanism, resulting in the formation of a pentafluoroben-zyl structural unit at the polymer terminus (Scheme 4.4) [31, 32]. Thus, poly(perfluoro-2-methylene-l,3-dioxolanes) are generally thermally stable, and their decomposition temperature (Tj) in air is >300 C. 

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