Preparation of Narrowly Size Distributed Metal-Containing Polymer Latexes by Miniemulsion and Other Emulsion Techniques: Applications for Nanolithography

It is demonstrated that the miniemulsion polymerization technique allows the preparation of highly uniform and practically monodisperse latex particles containing a hydrophobic metal complex like platinum(II)acetylacetonate, indium(III)acetylacetonate, zinc(II)tetramethylheptadionate, zincphthalocyanine, and chromium(III)benzoylacetonate, respectively, with different loading capacities. For some platinum and iron complexes, the homogeneity of the latexes can be improved even further by adapted emulsion techniques. By choosing different amounts of surfactant, we can adjust the particle size between 100 and 260 nm. To obtain larger particles up to 370 nm for a given metal complex, we performed an additional feeding of monomer. In this way, the particles can be easily modified by changing the polymer or the copolymer composition. Using a pure polymer core and semicontinuously adding a complex/monomer mixture leads to an increased size of the particles, which can contain additional metal complexes. The methodology was also applied for the preparation of alloyed Fe/Pt particles. The concentration relations were analyzed by inductively coupled plasma spectroscopy (ICP) and, mostly, energy-dispersive X-ray spectroscopy (EDX). When particles are deposited onto a substrate, the high homogeneity of the particle size results in hexagonally well-ordered monolayers of the metal-containing polymer particles. Such an encapsulation of metal complexes into particles of defined size makes them suitable for a wide variety of applications, especially in the context of nanolithography.