Abstract:

Narrow-dispersed poly( aminopropyl /phenylsilsesquioxane) ( PAPSQ) microspheres were prepared via the hydrolytic cocondensation of γ-aminopropyltriethoxysilane ( APS) and phenyltriethoxysilane ( PTES) under the action of alkali catalysts,and the effects of the APS-to-PTES molar ratio,the water-to-silicon molar ratio,the cosolvent type,the tetramethylammonium hydroxide ( TMAOH) concentration and the total monomer concentration on the morphology and size of PAPSQ microspheres were explored by using a scanning electron microscope and a particle size analyzer. Moreover,the formation mechanism of the microspheres under different reaction conditions was investigated. The results indicate that ( 1) when ethanol is used as the co-solvent,narrow-dispersed microspheres with a diameter ranging from 0.7 to 1.0 μm are obtained at an APS-to-PTES molar ratio of 1 /4,a water-to-silicon molar ratio of 50,a TMAOH concentration of 0.025mol /L and a total monomer concentration of 0.25mol /L; ( 2) with ammonia as the catalyst and with isopropanol as the co-solvent,microspheres with large size and broad distribution can be obtained; ( 3) only partial spherical particles may form at lower water-to-silicon molar ratio and TMAOH concentration; and ( 4) no spherical particles can form if the total monomer concentration is too high.

Key words: γ-aminopropyltriethoxysilane, phenyltriethoxysilane, alkali catalysis, hydrolytic copolycondensation, microspheres, particle size, narrow dispersion