Platinum Metals Rev., 1996, 40, (2), 77
Preparation of Platinum/Polymer Nanocomposites
A simple method of producing metal/polymer composites, in which nanosized metal particles are homogeneously distributed throughout the polymer, would promote the development of a new generation of useful materials and devices. These devices would utilise the specific compositions and size-dependent electrical, chemical and magnetic properties of the composite. Some syntheses for specific applications have been reported, but no general synthesis for such a nanocomposite material has emerged.
Now, however, scientists at the University of Massachusetts, U.S.A., have developed a synthesis for making platinum/polymer composites (J. J. Watkins and T. J. McCarthy, “Polymer/Metal Nanocomposite Synthesis in Supercritical CO2”, Chem. Mater., 1995, 7, (11), 1991–1994). Their method involves the use of a supercritical fluid, in this case carbon dioxide. As a supercritical fluid, carbon dioxide offers great control over composite composition and structure and has a high permeation rate in polymers. Carbon dioxide is also a versatile process solvent and it is clean and environmentally friendly.
The precursor, dimethyl(cyclooctadiene)plat-inum(II), was dissolved into the carbon dioxide, and then sequentially impregnated into, and reduced in, thick films of the polymers poly(4-methyl-l-pentene) and poly(tetrafluoroethyl-ene). The reduction to metallic platinum was by hydrogenolysis and thermolysis. This resulted in platinum/polymer composites containing platinum clusters, of sizes from 15 to over 100 nm (depending upon preparation) being dispersed throughout the films. The sizes and distributions of the platinum clusters were measured by SEM and TEM.
In general, adjusting the permeation and reduction rates controls the size and distribution of the platinum clusters, and further work is being done to produce gradient structures.