Perfluorinated Sulphonic Acid Ion-Exchange Polymer Nation

Perfluorinated Sulphonic Acid Ion-Exchange Polymer (Nation) 

FIGURE 11.11. Structure of perfluorinated sulphonic acid (Dupont Nafion) backbone. 

Nafion is also used as a suitable matrix for enzyme immobilization. In their study Fortier et reported a one-step preparation of GOx/Nafion film on a Pt electrode. At its optimal performance conditions, the Pt/GOx/Nafion electrode also served as a membrane barrier to oxidizable anionic species. However GOx decreased the ability of the Nafion film to exclude anionic interferents. 

Poly(ester Sulphonic Acid) lon Exchange Polymer (Eastman AQ Polymer) 

Similar to the behavior of Nafion, poly(ester sulphonic acid) ionomers selectively exclude anionic species and large particles, but cations and neutral molecules are permeable. Of the three Eastman Kodak AQ 29, AQ 38, and AQ 55 polymers, AQ 55 (see the polymer backbone in Fig. 11.12) is the most studied and most applied in biosensor preparation. Wang and coworkers described have features of this polymer as an electrode material, including strong affinity toward hydrophobic counterions, prevention of electrode fouling from proteins, stability of the polymer film on the electrode, ability to preconcentrate catalysts in the film, and lowering the overpotential of many species difficult to oxidize or reduce. Several workers also showed that this poly(ester sulphonic acid) polymer is very stable as an organic phase electrode material.  

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