Silver doped with acidic/basic polymers: Novel, reactive metallic composites

We report the preparation and properties of metallopolymeric composites with acidic and basic properties. The composites are prepared via the recently developed method of entrapping organic molecules within metals. Specifically, we describe the entrapment of the polyacid Nafion or the polybase poly(vinylbenzyltrimethylammonium hydroxide) within silver. The resulting acidic or basic metallic composites decrease or increase, respectively, the pH of water through an ion-exchange process. Furthermore, silver doped with Nafion can be employed as an acid catalyst, as shown for the pinacol-pinacolone rearrangement and for the dehydration of an alcohol. Characterization of these novel materials via microscopy and adsorption studies reveals a three-level hierarchical structure: clusters of approximate to 10 mu m in size built from approximate to 1 mu m aggregates of approximate to 100 angstrom silver crystals. Thermogravimetric analysis of the entrapped polymers reveals a catalytic effect of the metal on this process. The two polymers are entrapped differently, and the differences are discussed. Applications ranging from ion-exchange electrodes to bifunctional catalysts are envisaged.