Modification of SiO2Surfaces by Reaction with Acetals, Ketals, Orthoesters, and Orthocarbonates

✍ Scribed by Bruno R. Guidotti; Erwin Herzog; Felix Bangerter; Walter R. Caseri; Ulrich W. Suter

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 119 KB
• Volume: 191
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1997.4903

✦ Synopsis

reported a few times, organosilanols (9); these treatments SiO 2 was treated with compounds of the type C(OR) 4 (orthocar-yield strongly bound alkoxy or silyloxy species, respectively, bonates), RC(OR) 3 (orthoesters), and RRЉC(OR) 2 (acetals under release of water. and ketals) in CCl 4 under reflux. The resulting modified surfaces While methoxysilanes react already at 100-200ЊC with were analyzed with IR, 1 H NMR, and 13 C NMR spectroscopy, and SiO 2 surfaces, chlorosilanes require temperatures of 300-TGA. The initial compounds decompose, leaving on the surface 400ЊC (10). Usually the surface modifications with alcohols only OR groups that are tightly bound. The reaction with orthocar-

are performed above 130ЊC (11). It has been reported that bonates and orthoesters is more effective than that with acetals or most reagents react with only about half the amount of surketals, and the SiO 2 surface can be covered with OR groups to a face hydroxyl groups, even if the molecules are so small that high degree. The adsorption of polymers is restricted by the bound organic species. The modified surfaces are similar in many respects it is expected that steric effects would not prevent complete to those of alcohol-treated silicas, but the reaction proceeds at reaction (12). lower temperatures than those typically used for silica modifica-Silica modification with compounds such as CH 3 (CH 2 ) ntion with alcohols.