Synthesis functionalized organosiloxanes

Ellis, S. R. M. 1971. Vapor phase extraction process. Br. Chem. Eng. 16 358. Elsbernd, C. S. 1988. Synthesis, kinetics, and supercritical fluid fractionation studies of functional organosiloxanes and their incorporation into segmented copolymers. Ph.D. diss., Virginia Polytechnic Institute and State University. 

Elsbernd, C. S., M. Spinu, V. J. Krukonis, P. M. Gallagher, D. K. Mohanty, and J. E. McGrath. 1990a. Synthesis and fractionation studies of functionalized organosiloxanes. In Silicon-based polymer science, ed. J. M. Zeigler and F. W. G. Fearon, 145. Advances in Chemistry Series No. 224. Washington, D.C. American Chemical Society. 

As it is well known, the (Si-0) bond in organosiloxanes may be considered to be polar or partially ( 50%) ionic.(12) Therefore, it can be cleaved by the attack of strong acids or bases. This is the main rationale behind the "equilibration" route to the synthesis of a wide variety of functionally terminated siloxane oligomers(12-14) from cyclic siloxanes and a.ordifunctional disiloxanes as shown in Scheme 3. 

Organically modified MCM-41 can be prepared directly by using alkoxysilanes or organosiloxanes in the synthesis mixture thus coating the internal wall of the pores with functional groups. An example of a condensation reaction of an alcohol with the surface silanol groups to modify the pore wall is shown in Figure 7.22. 

In contrast, the synthesis of the initiator functionality and the modification of the poIy(siloxane) is only one single step for TMP using an easily available diazonium compound 2 with a yield of about 60-80 %. Structure verification and determination of the initiator group content could be done by h NMR spectroscopy. GPC analysis showed that the modified poly(organosiloxane)s retain their original molecular weights. About 4-8 initiating sites have been attached onto the silicone backbone. Due to the chromophores, AMP and TMP are yellow products. 

Polymeric initiators based on azo or triazene modified poly(organosiloxane)s can be used to synthesize graft copolymers with silicone backbone and thermoplastic side chains. The azo functionality has some advantages such as lower thermal stability, known reaction mechanism, no homopolymer formation and cleaner graft products. However, the synthesis of the triazene polymeric initiators requires fewer synthetic steps. The graft products microseparate but form stable films. 

From the above-stated it follows that synthesis of poly-organosiloxane xerogels with a bifunctional surface layer is possible when a use is made of functional groups of various nature. In this case the composition of a surface layer can be varied over a wide range (in our experiments the SH/NH2 ratio was equal to 4 0, 3 1, 2 2, or 1 3). 

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