文摘
A series of sulfonated diamines were synthesized which were further used to obtain relevant sulfonatednaphthalenic copolyimides. Tough and ductile membranes were cast from solutions of the copolyimides indimethylsulfoxide, which exhibit high ion-exchange capacity and high water uptake. The protonic conductivityof the membranes equilibrated with water lies in the range 1.0-8.6 S/m, at 25 C, being of the same orderof magnitude as that reported for perfluorinated acidic membranes. The values of the transport number ofprotons and sodium ions are close to the unit for very dilute electrolyte solutions, but they lie in the range0.80-0.90 for moderate concentrations. The membranes exhibit rather high electroosmotic permeability. Thesimilarity of the diffusion coefficients of protons and water in the membranes suggests that the Grottusmechanism governs the protonic conductive process in the acidic membranes equilibrated with water.