Perfluorinated morphology

Gierke, T. D., Munn, G. E. and Wilson, F. C. 1981. The morphology in Nafion perfluorinated membrane products, as determined by wide-angle and small-angle x-ray studies. Journal of Polymer Science Polymer Physics 19 1687-1704. 

For instance, the Dow experimental membrane and the recently introduced Hyflon Ion E83 membrane by Solvay-Solexis are "short side chain" (SSC) fluoropolymers, which exhibit increased water uptake, significantly enhanced proton conductivity, and better stability at T > 100°C due to higher glass transition temperatures in comparison to Nafion. The membrane morphology and the basic mechanisms of proton transport are, however, similar for all PFSA ionomers mentioned. The base polymer of Nation, depicted schematically in Figure 6.3, consists of a copolymer of tetrafluoro-ethylene, forming the backbone, and randomly attached pendant side chains of perfluorinated vinyl ethers, terminated by sulfonic acid head groups. °... 

The applications of commercially available perfluorinated compounds have been reported in a number of recent pub-Kcations [395-397]. In the presence of perfluorocarboxylic acids, the current efficiency increased, and surface morphology... 

Besides the simple effects of mesophase stabilization by increased polar-apolar incompatibility and modification of mesophase morphology due to size effects, there are additional specific effects based on the lipophobicity (R[ -RH incompatibility) and rigidity of perfluorinated segments. In this respect it is important to... 

In scientific terms, the unusual ion-clustered morphology of the perfluorinated ionomer polymers has provoked much interest. Clearly, the microphase-separated structure that is revealed through various types of experiments is strongly related to their unusual transport properties. It is important to refine our understanding of this relationship in order to exploit these materials in various electrochemical applications. 

In summary, I have discussed a semi-phenomenological elastic theory for ion clustering in ionomers. The theory is consistent with observed trends in perfluorinated ionomers. I have also demonstrated the percolatlve nature of ion transport in these ionomers and computed quantitatively their tensile modulus. Finally, I have discussed the Influence of morphology on ion selectivity in perfluorinated ionomer blends. In particular, I have pointed out that an universally preferred morphology beneficial to all blends does not exist the ideal morphology must be individually determined based on component properties. Most of the theories and conclusions here are very general and applicable to other composite polymer systems. 

Thus the study of these perfluorinated ionomers is important not only because of the fundamental significance of their ion clustered morphologies, but also becuase this research will help to provide a scientific foundation for future developments in membrane science. The work which is discussed in this monograph represents the efforts of many workers to establish this foundation. 

Studies of these perfluorinated membranes in dilute and in concentrated solution environments still leave many unanswered questions about the nature of membrane transport properties. However, the obvious importance of these polymers in membrane separation applications, coupled with the fundamental significance of their ion clustered morphology, makes the continued study of these materials a fruitful area of research for the future. 

T.D. Gierke, G.E. Munn and EC. Wilson, Morphology of Nafion perfluorosulfonated membrane products, as determined by wide- and small-angle X-ray studies, J. Polym. Sci., Polym. Phys. Ed., 1981, 19, 1687-1704 W.Y. Hsu and T.D. Gierke, Elastic theory for ionic clustering in perfluorinated ionomers, Macromolecules, 1982, 15, 101-105. 

Perfluorinated Nation Dimethylformamide, The spherulitic crystalline morphology of PVDF showed strong... 

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