Structure and Adsorption of 3-acryloxypropyltrimethoxysilane


The adsorption of 3-acryloxypropyltrimethoxysilane (APMS) onto silica and structures formed from the adsorption were studied using gravimetric analysis and NMR. APMS molecules were hydrolyzed at room temperature and then condensed at 110 °C with other APMS molecules or on a silica surface. After heat treatment at 110 °C, the alkyl groups of APMS from the bulk species or the immobilized species on the silica surface were investigated using 13C cross-polarization, magic-angle spinning (CP-MAS) NMR. 29Si MAS and CP-MAS NMR techniques showed that most of the APMS silanol groups were condensed to 27% T2 and 73% T3 species during heat treatment at 110 °C. The condensed APMS was then pyrolized at 600 °C. Most of the APMS alkyl groups had been replaced with oxygen during pyrolysis resulting in 21% Q3 and 79% Q4 species. The differences in the masses of APMS following the heat treatment steps (at 110 °C and 600 °C) made it possible to confirm the nature of the chemical species present. From the gravimetric measurements, there were 26% T2 and 74% T3 species after 110 °C heat treatment and 18% Q3 and 82% Q4 species after pyrolysis. The results from NMR and gravimetric analysis were in good agreement. A Langmuir isotherm was applied to estimate the saturated layer coverage of APMS, which was determined using the mass profile of APMS adsorbed on a high-surface-area fumed silica; it showed the saturated layer coverage to be about 0.6 mmol/100 m2.




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© 1999 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Jan 1999