What is the difference in use of methoxysilyl and ethoxysilyl groups in silane coupling agents?
The hydrolysis of alkoxysilyl groups is faster for methoxysilyl groups than for ethoxysilyl groups.
Hydrolytic Activity of Alkoxy Groups
In general, the methoxy group (-OCH₃) is more reactive (hydrolyzable) than the ethoxy group (-OC₂H₅).
Under acidic conditions, the reaction is faster with fewer alkoxy groups, so the order of hydrolysis speed is as follows;
Dimethoxy > Trimethoxy > Diethoxy > Triethoxy.
On the other hand, under basic conditions, the order is as follows;
Trimethoxy > Dimethoxy > Triethoxy > Diethoxy.
Hydrolysis of the methoxysilyl group produces methanol, and hydrolysis of the ethoxysilyl group produces ethanol, so if you are concerned about the generation of methanol, please use the ethoxysilyl group (KBE series).
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