Siloxane Oligomers with Organofunctional Termination Si—R—X

The type and nature of the (R) group also has a major influence on the chemical reactivity of the functional group (X) towards the others. Since (R) can be aliphatic or aromatic in nature, the reactivity of the same end group (e.g. —OH), will be quite different depending on the type of the (R) group that is is linked to (e.g. —CH2—OH 

3 Synthesis of ot,td-Organofunction ally Terminated LMsiloxanes Precursors for the Functionally Terminated Oligomers 

Although there are several possible methods for the synthesis of organofunctionally terminated disiloxanes, hydrosilation reactions have become the most popular and practical process. Hydrosilation is the term used for the addition of silicon hydrides 

Synthesis ofa, D-GlycidoxypropyI-Terminated Tetramethyldisiloxane via Hydrosilation Reactions 50) 

Although the actual reaction mechanism of hydrosilation is not very clear, it is very well established that the important variables include the catalyst type and concentration, structure of the olefinic compound, reaction temperature and the solvent. used 1,4, J). Chloroplatinic acid (H2PtCl6 6 H20) is the most frequently used catalyst, usually in the form of a solution in isopropyl alcohol mixed with a polar solvent, such as diglyme or tetrahydrofuran S2). Other catalysts include rhodium, palladium, ruthenium, nickel and cobalt complexes as well as various organic peroxides, UV and y radiation. The efficiency of the catalyst used usually depends on many factors, including ligands on the platinum, the type and nature of the silane (or siloxane) and the olefinic compound used. For example in the chloroplatinic acid catalyzed hydrosilation of olefinic compounds, the reactivity is often observed to be proportional to the electron density on the alkene. Steric hindrance usually decreases the rate of 

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