Use of p-Toluenesulfonic Acid for the Controlled Grafting of Alkoxysilanes onto Silanol Containing Surfaces: Preparation of Tunable Hydrophilic, Hydrophobic, and Super-Hydrophobic Silica

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• 作者：Nuria Garc&iacute ; a ; Esperanza Benito ; Julio Guzmá ; n ; Pilar Tiemblo
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：April 25, 2007
• 年：2007
• 卷：129
• 期：16
• 页码：5052 - 5060
• 全文大小：411K
• 年卷期：v.129,no.16(April 25, 2007)
• ISSN：1520-5126

文摘

The modification of Aerosil 200 has been carried out using methoxysilanes in toluene reflux,with p-toluenesulfonic acid as the catalyst. Both trimethoxyalkyl silanes (methyl, ethyl, propyl, butyl, hexyl,octyl, and octadecyl) and trialkylmethoxy silanes (trimethyl and dimethyloctyl) have been used. The surfacehas been studied by ²⁹Si NMR, ¹³C NMR, elemental analysis, thermogravimetry, water contact angle, andBET analysis. When incorporating trimethoxysilanes, a plateau of modification was achieved after 1 h ofreflux, while when using trialkylmethoxy silanes, a longer time of about 7 h was required. The averagenumber of molecules incorporated in both cases has been well above those reported by other authors insimilar reactions and in much shorter times. Depending on the modification agent and on the experimentalconditions, the resulting organosilicas are in seven cases superhydrophobic, in three cases hydrophobic,and in two cases hydrophilic. Two structural origins for superhydrophobicity have been identified in thesesamples: almost complete disappearance of water accessible surface silanols (smallest methoxysilanes)and shielding of would-be water accessible surface silanols by long aliphatic tails. These features can bevery precisely controlled.