Nonfluorinated ionomer membranes

Nonfluorinated ionomer membranes Numerous different types of nonfluori-nated ionomer membranes, among them ionomer membranes based on styrene polymers and copolymers containing polystyrene units [7], arylene main-chain polymers of different poly(phenylene) [8], poly(ethersulfone) [9-11], poly(etherketone) [12-15], poly(phenylene oxide) [16,17], poly(phenylene sulfide) [18] types, and such membranes based on an inorganic backbone like poly(phosphazenes) [19,20], poly(siloxane)s [21], have been developed in the past years... 

The use of low-cost basic polymers instead of Nation is an interesting alternative [19,20].The development of new polymers for ionomer membranes including perfluorinated ionomers, partially fluorinated ionomers, nonfluorinated ionomers, high-molecular/low-molecular composite membranes as well as novel polymer modification processes and novel membrane materials is summarised in [21]. 

Kerres J, Xing D, Schonberger F (2006) Comparative investigation of novel FBI blend ionomer membranes from nonfluorinated and partially fluorinated polyaryiene ethers. J Poiym Sci B Polym Phys 44 2311-2326... 

Use of sulfonated polymers as the proton-conductive component in the fuel cell membranes at T < 100°C Use of nonfluorinated ionomers physical and/or chemical cross-linking of the fuel cell membranes Use of nonfluorinated ionomers physical and/or chemical cross-linking of the fuel cell membranes Development of organic-inorganic composite membranes, based on our cross-linked ionomer membrane systems, in which the inorganic membrane component serves as water storage or even contributes to H -conduction Use of commercially available polymers for chemical modification and membrane formation, which avoids expensive development of novel polymers... 

Table 8.5 Properties of nonfluorinated and partially fluorinated ionomer membranes...

Kerres et al., among others, developed the acid-base blend membranes from sulfonated polymers and aminated or other basic polymers [98] and concluded that the protonation of the basic groups is incomplete if the base is too weak [99]. Very recently, Frutsaert et al. [70] synthesized novel polymers for the development of high temperature PEMFC membranes comprising a blend of s-PEEK and a fluorinated copolymer bearing imidazole functions as pendant groups. The extensive work on intermediate temperature fuel cell membranes are well reviewed in Chap. 4 of this book including polybenzimidazole as the basic component and sulfonated and phosphonated ionomers of either nonfluorinated or partially fluorinated backbones as the acidic component. 

From the reviewed work, it can be concluded that obviously the use of partially fluorinated aromatic cationomers as ionical cross-linkers leads in most cases to better chemical and thermal stabilities of the blend membranes than if nonfluorinated cationomers would be applied as acidic blend components. Among aU acidic cross-linkers, the sulfonated and partially fluorinated ionomer S9 (Fig. 4.5) leads to the best chemical stability of the referring base-excess PBI blend membranes. 

Dependence of the membrane properties from membrane type (nonfluorinated and partially fluorinated ionomer). We have developed partially fluorinated covalently cross-linked membranes by reaction of disulfmated poly (ethersul-fones) with pentaflnorobenzene sulfochloride and different cross-hnkers [90]. The scheme for the preparation of such partially fluorinated covalent ionomer networks is given in Fig. 8.10. The obtained membranes showed high H -conductivities and moderate SW. In Table 8.5, some of the properties of one... 

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