1976 Volume 49 Issue 12 Pages 3389-3393
The Aerosil surface was treated with C1–C4 alcohols under both high-pressure and low-pressure conditions. The high-pressure treatment was carried out at various temperatures up to 250 °C using an autoclave, while the low-pressure treatment was done at 280 °C under vapor pressure at room temperature. The surface changes were followed by IR spectroscopy, and the carbon content was determined. The degrees of alkoxylation (OR groups/100 Å2) of the Aerosils treated sufficiently under low pressures were 1.3–1.6, approximately equal to the amount of OH isolated before the treatment, while the values under high pressures reached 2.3–3.4, equal or near to the amount of the total OH. The values for methoxylation were particularly higher, while those for t-butoxylation were quite low. These results, in addition to the observation of the IR spectra, indicate that the isolated OH groups are predominantly esterified under low pressures, while under high pressures the vicinal OH groups are esterified as well, and the opening of the siloxane bonds occurs easily in the case of methoxylation. The stability of the alkyl groups on the Aerosil against heating decreased in the order of: primary>secondary>tertiary.
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