Zinc oxide powder was dry-ground by a vibrationmill equipped with an alumina vessel or a plastic vessel with balls. The intensity of the ESR peaks and the wetting property of the ground powder were measured. The root-mean-squared atrain and the crystallite sizes of the powder were determined by Stokes-corrected Fourier analysis of the X-ray peaks. It was clarified that the wettability of the surface of the zinc oxide particle increased with increasing the intensity of the ESR peaks accompanied by red-yellow coloring in alumina vessel grinding, while in plastic vessel grinding the wettability increased with the ESR peaks at the beginning but decreased at the further grinding exhibiting real clear yellow.
We have prepared some 1, 4-naphthoquinones (1) and maleimides (2), as mercocyanine dyes, with a terminal triethoxysilyl group connected directly with a network of Si-O matrix gels in the sol-gel processing. The reactions of 2, 3-dicyano-1, 4-naphthoquinones and maleic anhydrides with amino-propyltriethoxysilane or aminopropylmethyldiethoxysilane gave dyes 1 and 2 with a terminal triethoxysilyl or diethoxysilyl group (yields 22-72%). The absorption spectra of merocyanine dyes with terminal triethoxysilyl group in gel film were different from those in sol, and this result was interpreted by PPP-MO calculations. Dyes with terminal triethoxysilyl group exhibited a higher solubility in ethanol-water mixture. The hydrolysis and condensation of the merocyanine dye were performed under the silica-sol processing conditions to examine the reactivity of terminal triethoxysilyl group.
The polymerization of cyclic dimethylsiloxanes in the presence of pigments was studied by an ampoule method at 50°C. The products were polydimethylsiloxanes (PDMS), whose molecular weight were 200,000 and 8,700 in the reaction with kaolinite and prussian blue, respectively. The results of GC/MS measurement indicated that cyclic oligomers formed in the first step from D4 by kaolinite were not D8, D12, and D16, which were kinetically controlled species, but D5, D6, and D7, which were thermodynamically controlled ones. The results of the reaction between cyclic siloxanes and kaolinite in the presence of hexane as a solvent indicated that the lower the concentration of cyclic siloxane was, the lower the molecular weight of product became. In, the case of 0.1% solution of D3, D4, and D5, the final products had an identical composition, D3 : D4 : D5 : D6=4 : 80 : 15 : 1. These results show that the meeting of the two ends of a linear species is the main factor determining the distribution of cycle siloxanes, where a low monomer concentration leads to self-end-to-end ring closure, while polymerization among different molecules is encouraged at a high monomer concentration.