Alkoxy-Grafted Surfaces

We then studied group 5 metals, especially tantalum-for which the laboratory already had great experience. Because of the studied reaction, alkyl or hydride-type compounds such as those developed in the laboratory could not be employed. Consequently, we became interested in alkoxo-type derivatives, either synthesized by reaction of the grafted complex with an alcohol or obtained by direct synthesis starting from an alkoxy-tantalum compound grafted on silica. In all cases, resulting complexes have been characterized by surface organometallic chemistry techniques, especially EXAFS and solid-state NMR (ID and 2D with C-labeled compounds). Indeed various compounds bonded by one, two or three surface bonds have been prepared and characterized. 

Scheme 7 a Reaction mechanism when sodium persulphate was used as hydroxylating agent for the polymer (P-H). b Decomposition of hydroxylated polymer P-OH at the surface, in the presence of ceric ammonium nitrate generated alkoxy radicals (P-0 ) which initiated the grafting... 

Commercially important is also the use of ceric salts, which can reduce alcohols to alkoxy radicals and enable grafting from cellulose and other surfaces with... 

The grafting of alkoxy groups on various silicon surfaces has been the subject of a number of studies [44-54]. It can most conveniently be obtained by reaction of the hydrogenated Si surface with alcohols [44-49,52,53] ... 

In the same way as for the alkyl-modified Si surfaces, the surface concentration of grafted alkoxy chains appears to be limited by steric hindrance. Coverages from 1/3 to 2/3 on (111) Si surfaces have been reported [54,179,180]. 

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