Nafion^® membranes are the most commonly used proton conductor for polymer electrolyte membrane fuel cells (PEMFCs) because they have high proton conductivity and excellent chemical, mechanical, and thermal stability. However, when used in direct methanol fuel cells (DMFCs), the high methanol crossover of Nafion^® results not only in lower fuel efficiency but also in a lower overall voltage performance, which impedes their commercial development in this application. Our work presents a new method to modify Nafion^®, that is, impregnating polyamidoamine generation 0 (PAMAM G0) into Nafion^® to form crosslinking, thus reduce the membrane swelling ratio and decrease the methanol crossover. Besides the reduction of methanol crossover, this modification is expected to keep high proton conductivity due to the excess number of amino groups in PAMAM. Modified membranes were characterized using X-ray photoemission spectroscopy (XPS), atomic force microscopy (AFM), and thermogravimetric analysis (TGA). Measurements of water uptake, methanol permeability, and proton conductivity of membranes were carried out, as were fuel-cell stack tests of membrane electrode assemblies (MEAs) prepared from these modified membranes.

In a separate, but related project, bifunctional perfluoropolyethers of the general formula F₂C=CF-O-(R_F-O)_n-CF=CF₂, where R_F = -CF₂-CF₂-CF₂-, -CF(CF₃)-CF₂-, or -CF₂-CF₂-, are accessible from difluoromalonyl difluoride or oxalyl fluoride by fluoride ion-assisted ring opening of hexafluoropropylene oxide. If n is smaller than three (3), the bifunctional monomers can easily be separated and obtained in pure form. The chemical and spectroscopic properties of these compounds as well as details of their syntheses will be discussed.