Nanophase separated perfluorinated ionomers as sol-gel polymerization templates for functional inorganic oxide nanoparticles

摘要

Mauritz et al. exploited the polar/nonpolar nanophase-separated morphologies of Nafion (R) perfluorosulfonic acid membranes, as well as a chemically modified Nafion (R) precursor film, as interactive templates capable of directing sol-gel hydrolysis -> condensation polymerizations of inorganic alkoxides and organoalkoxysilanes and the geometrical distribution of inorganic oxide or organically modified silicate nanophases that result upon drying. This paper reviews our studies involving Nafion (R) in situ sol-gel reactions of alkoxides of silicon, titanium, aluminum, zirconium, and organoalkoxysilanes and combinations of these monomers. Also discussed are similar studies by other investigators. We discuss spectroscopic, microscopic, x-ray scattering, thermal, mechanical tensile, dynamic mechanical, dielectric relaxation, and gas permeation tools that were employed to interrogate the structures and properties of these heterogeneous materials over a range of dimensional scales. Methods of tailoring the energetic environment, or polarity, within the cluster domains by insertion of inorganic oxide or organically-modified silicate nanostructures are presented. Finally, we discuss the potential for these nanocomposite membranes within a number of areas including gas and liquid separations technology, catalysis, and proton exchange membranes for fuel cell technology.