An Infrared Study of the Amine-Catalyzed Reaction of Methoxymethylsilanes with Silica

✍ Scribed by L.D. White; C.P. Tripp

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 108 KB
• Volume: 227
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.2000.6895

✦ Synopsis

A thin film infrared technique was used to investigate the reaction of methoxysilanes and amines with the silica surface. The lowfrequency region contains bands due to Si-O-Si modes that are used to distinguish between hydrogen-bonded and chemisorbed species. It is shown that the competitive adsorption of amines and CH 3 OSi(CH 3 ) 3 differs from the results obtained using (CH 3 O) 2 Si(CH 3 ) 2 or (CH 3 O) 3 SiCH 3 . The monomethoxysilane does not displace preadsorbed triethylamine whereas the triethylamine is displaced from the surface by both (CH 3 O) 2 Si(CH 3 ) 2 and (CH 3 O) 3 SiCH 3 . In the reverse sequence, the triethylamine displaces all three methoxysilanes on the surface. When 1 : 1 mixtures of methoxysilanes and triethylamine (or propylamine) are co-added to silica, the amine preferentially adsorbs and is only displaced by subsequent chemisorption of the silane. The implication of these results for using a two-step amine-catalyzed reaction of methoxysilanes on silica is discussed.