The Wettability of Ethyl- and Vinyltriethoxysilane Films Formed at Organic-Liquid/Silica Interfaces

摘要

Critical surface tensions and water contact angles were determined for adsorbed films of ethyltriethoxysilane and vinyltriethoxysilane on silica and alpha-alumina. The films were formed by retraction from hydrocarbon solution. Studies were also made of film resistance to desorption and alteration when in prolonged contact with water. The vinyltriethoxysilane films were generally more oleophobic and more hydrophobic than the films formed by the ethyl analog. The vinyltriethoxysilane films were also more resistant to disruption and desorption when contacted with water. Neither vinyl- nor ethyltriethoxysilane formed strongly held films on alpha-alumina. The addition of low-molecular-weight organic acids or bases to the adsorbate solutions resulted in both the ethyl-and vinyltriethoxysilane forming hydrophobic and water resistant films on silica and alpha-alumina. The results suggest that the adsorption process involves the adsorbate molecules reacting with silanol groups on the silica to form siloxane linkages to the surface and reacting with themselves to form adsorbed siloxane polymer. The properties of the resulting film will depend upon the number of surface attachments and the extent of crosslinking between adsorbate molecules. (Author)