Preparation and properties of polyethoxysilsesquioxane-C60 hybrids

Free-standing films of C-60-polyethoxysiloxane hybrids were prepared, and their optical limiting properties were evaluated. Triethoxysilylated C-60, with a formula of H3C60[Si(OEt)(3)](3), was synthesized by the hydrolysilylation of C-60 with triethoxysilane in the presence of platinum catalyst. C-60-polyethoxysiloxanes were prepared by a cohydrolytic polycondensation of triethoxysilylated C-60 with tetraethoxysilane in a molar ratio of Si/C-60 = 10-1000 under nitrogen flow. The molecular weight of C-60-poly-ethoxysiloxane increased with a decrease of Si/C-60- Transparent and flexible free-standing films were prepared by aging an ethanol solution of C-60-polyethoxysiloxane at 80 degrees C for 6-8 days. The mechanical strength and Young's modulus increased with a decrease in Si/C-60. These free-standing films showed an optical limiting property, for which the threshold value decreased from 1163 mJ/cm(2) (Si/C-60 = 1000) to 130 mJ/cm(2) (Si/C-60 = 10) with a decrease of Si/C-60. (C) 2007 Wiley Periodicals, Inc.