Reactivity silsesquioxanes

The fact that silsesquioxane molecules like 2-7 contain covalently bonded reactive functionalities make them promising monomers for polymerization reactions or for grafting these monomers to polymer chains. In recent years this has been the basis for the development of novel hybrid materials, which offer a variety of useful properties. This area of applied silsesquioxane chemistry has been largely developed by Lichtenhan et al With respect to catalysis research, the chemistry of metallasilsesquioxanes also receives considerable current interest. As mentioned above, incompletely condensed silsesquioxanes of the type R7Si70g(0H)3 (2-7, Scheme 4) share astonishing structural similarities with p-tridymite and p-cristobalite and are thus quite realistic models for the silanol sites on silica surfaces. Metal... 

Lai et al. (3) prepared reactive polyhedral oligomeric silsesquioxane derivatives,... 

On the basis of all the information collected from this MS study, it is possible to propose a mechanism for the formation of silsesquioxane a7bi (Fig. 9.10). Silsesquioxanes with learly stages of the synthesis and react very quickly to form more condensed species. It is assumed that the very reactive a1 bi will not be formed again by hydrolysis reactions of more condensed species this means that the reactions in which albi takes part are effectively irreversible and that the compound will only be available for the reactions in the early stages of the synthesis. Silsesquioxanes with 2react with each other to form the more condensed silsesquioxanes with 4[Pg.226]

This fact is corroborated by the chemical reactivity of these materials R groups located at the surface are chemically accessible and highly reactive. For example, complexation of phenyl groups of a CgHsSiOj 5 xerogel by Cr(CO)3 in phenyl/silsesquioxanes is easy80 and HSiOi 5 can be transformed to siliconoxynitride by reaction in a flow of NH381. 

Lee D W and Kawakami Y (2007) Incompletely condensed silsesquioxanes formation and reactivity. Polym J 39 230-238... 

Most of the contributions in Chapter IV deal with this area of research. Commercial interest is centered on the field of silicones with defined silicon substitution patterns, molecular weight, crosslinking degree and the study of structure-property correlations. In constrast the academic interest focusses on topics that may be recognized as "old" problems, such as "silyl modified surfaces", "synthesis and reactivity of silsesquioxanes", and "luminescent silicon". The reader will find answers to these problems in this chapter. 

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