Dihydroxyaluminum Carboxylate Nanoparticles With Narrow Size Distribution: Synthesis, Characterization and Use for High Optical Transparency Protective Polymeric Coatings a Hazem Khalil, Hans-Ju ¨rgen Gla¨sel, Luise Wennrich, Andrea Prager, Michael R. Buchmeiser* Introduction Organic polymers are flexible, tough, and easy to process; however, they can also be relatively easily damaged, whether chemically or mechanically. In contrast, inorganic materials are typically much harder, have better barrier properties, good chemical stability, however, are also brittle and more difficult to process. Organic–inorganic nanocom- posites yield a combination of these properties, resulting in hard, tough, chemically stable, and durable materials. [1] Full Paper H. Khalil, H.-J. Gla ¨sel, L. Wennrich, A. Prager, M. R. Buchmeiser Leibniz-Institut fu ¨r Oberfla ¨chenmodifizierung, Permoserstr. 15, D-04318 Leipzig, Germany M. R. Buchmeiser Institut fu ¨r Polymerchemie, Lehrstuhl fu ¨r Makromolekulare Stoffe und Faserchemie, Universita ¨t Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany Fax: þ49 0 3412352584; E-mail: michael.buchmeiser@ipoc.uni-stuttgart.de : Supporting information for this article is available at the bottom of the article’s abstract page, which can be accessed from the journal’s homepage at http://www.mme-journal.de, or from the author. Nano-sized bis(dihydroxyaluminum)maleate particles (ALMAL) were prepared via a high- temperature precipitation reaction from different Al-alkoxides and maleic acid in different solvents. Variations in the reactants were carried out to identify the optimum reaction conditions that lead to particles <30 nm in diameter with narrow particle size distributions and without formation of a secondary amorphous phase. A disc centrifuge was used to characterize the particles in terms of particle size distribution. ALMAL-containing, epoxy- based nanocomposites were prepared with ALMAL-loadings up to 30 wt.-% and thermally cured. The cured coatings possessed excellent scratch and abrasion resistance, surface hard- ness and were highly transparent (T>95%). In order to study the effect of the nature of nanoparticles on the final properties of the coatings, aluminum malate (ALMALAT), and aluminum terephthalate (ALTER- EPHTHAL) nanoparticles as well as the corresponding composite coatings were prepared and characterized. For comparison, surface-modified silica nanoparticles were used to evaluate the mechanical and optical behavior of the produced nanocomposite coatings. 170 Macromol. Mater. Eng. 2010, 295, 170–177 ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mame.200900240