Introduction

As reported in a previous chapter, under special conditions, perfluorosulphonic ion-exchange polymers behave as proton conducting materials. They possess a set of specific properties which make them suitable for use in various fields.

These ion-exchange materials are permeable only to cations-more specifically to protons – and also to water. Some polar organic solvents of low molecular weight can also permeate, to a much lower extent, through this perfluorosulphonic material. The easy water transport through the polymer prevents local drying which could otherwise occur during specific applications. At sufficiently high degrees of swelling, the electrical conductivity of perfluorosulphonic polymers in the protonated form is high and exceeds that of the material in other cationic forms.

NafionR is the leader of perfluorosulphonic proton conductors. Produced by Dupont de Nemours, it is commercially available in different forms: homogeneous or reinforced membranes, powders, tubes and solutions. From solutions of perfluorosulphonic acid or salt in organic solvents, gels and films can also be made. From NafionR, many kinds of composite material may also be prepared either by including small, dispersed particles inside the polymeric phase or by using it to coat solid electronic conductors. The adhesive power of this material is important when it is maintained in contact with a wide variety of supports.