Sulfonated perfluorovinyl monomer

Polymers with a polytetrafluoroethylene (PTFE) backbone and pendant perfluorosulfonate or perfluor-ocarboxylate groups have become commercially important materials, although they are expensive. The sulfonates were introduced as Nafion by Du Pont in the early 1970s and the carboxylates as Flemion by Asahi Glass in 1978. They are made by free-radical copolymerization of tetrafluoroethylene and perfluorovinyl monomers giving precursor copolymers, (XXII) and (XXIII), which can be post-functionalized by hydrolysis to generate sulfonic and carboxylic acid groups. The perfluorovinyl... 

Since PTFE was first synthesized more than 50 years ago, fluoropolymers have been produced by radical polymerization and copolymerizaton processes, but without any functional groups, for several reasons. First, the synthesis of functional vinyl compounds suitable for radical polymerization is much more complicated and expensive in comparison with common fluoroolefins. In radical polymerization of one of the simplest possible candidates—perfluorovinyl sulfonic acid (or sulfonyl fluoride—there was not enough reactivity to provide high-molecular-weight polymers or even perfluorinated copolymers with considerable functional comonomer content. Several methods for the synthesis of the other simplest monomer—trifluoroacrylic acid or its esters—were reported,1 but convenient improved synthesis of these compounds as well as radical copolymerization with TFE induced by y-irradiation were not described until 1980.2... 

Figure 1 describes the chemical structure of PFSA polymers, which was widely used as perfluorinated electrolytes for PEFCs. The structure is based on copolymers of tetrafluor-oethylene (TFE) and perfluorovinyl ether monomers with a side chain of sulfonic acid group. While many acid groups have been examined in... 

In 2000, Ford et al. [103] reported the synthesis of aromatic perfluorovinyl ether monomers containing sulfonamide and the sulfonic acid functionality for different apphcations, such as PEMFCs [105]. As in the former example. Ford et al. used... 

Using the optimal conditions for the radical terpolymerization of 4-[(a,/ ,/ -trifluorovinyl)oxy]bromobenzene with the fluoroalkenes, these authors reported the synthesis of new polymer electrolyte membranes based on fluoropolymers incorporating aromatic perfluorovinyl ether sulfonic acids [85,107]. In fact, a novel synthetic route for the preparation of perfluorovinyl ether monomer containing sulfonic functionalities, 4-[(a,, -trifluorovinyl)oxy]benzenesulfonic acid (TFVOBSA), was proposed. This monomer was synthesized in 72% overall yield. Further, the radical (co)- and terpolymerization of 4-[(a,, -trifluorovinyl)oxy] benzenesulfonyl chloride (TFVOBSC) with VDF, HFP, and PMVE (Fig. 2.25)... 

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