Synthesis and characterization of cationic silsesquioxane hybrids by hydrolytic condensation of triethoxysilane derived from 2-(dimethylamino)ethyl acrylate
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A new family of silsesquioxane hybrids was synthesized by hydrolytic condensation of a triethoxysilane precursor, R-Si(OCH2CH3)3, R = -CH2CH2CH2N[CH2CH2COOCH2CH2N(CH3)2]2, derived from 2-(dimethylamino)ethyl acrylate. Condensation of the triethoxysilane precursor proceeded as a homogeneous system in methanol in the presence of aqueous HF solution (3.2 %) to afford the water-soluble silsesquioxane hybrid having a high density of chemically bonded peripheral tertiary amino groups on the outermost surface, as confirmed by nuclear magnetic resonance and Fourier transform infrared analyses. The relatively low polydispersity (M w/M n = 1.33) and a reasonable molecular weight (M n = 2700), corresponding to species having 6–12 silicon atoms, were confirmed by size exclusion chromatography. The size of the silsesquioxane hybrid (1.7 nm) was also determined by X-ray diffraction. Co-condensation of tetraethoxysilane (TEOS) with the triethoxysilane precursor was carried out under different feed ratios, and water-soluble products were obtained in the cases of TEOS molar ratio up to 40 %. Quaternization reaction of the tertiary amine-containing hybrids with methyl iodide led to cationic silsesquioxane hybrids containing quaternized amine functionalities, which showed good solubility in polar solvents. Scanning force microscopy measurements indicated the formation of the cationic silsesquioxane hybrids having relatively narrow size distribution with average particle diameter (about 2.0 nm) without aggregation.
KeywordsSilsesquioxane Cationic hybrid Water-soluble nanoparticle Organic–inorganic hybrid
This work was supported by Saneyoshi scholarship foundation.
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