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. 

Table 2. General structure of (Si—X) terminated organosiloxane oligomers and important functional end groups...

An important advantage in the preparation of a,eo-functionally terminated siloxane oligomers, over the other telechelic systems, is the flexible polymerization chemistry of cyclic organosiloxane monomers and intermediates. This is mainly due to the partial... 

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. 

Besides HFC reaction of preliminarily prepared cyclic organosiloxanes with functional groups and difunctional organosilicon compounds, which give an opportunity to preserve cyclic groups in the polymeric backbone, hydride polyaddition is also widely used, which proceeds under soft conditions and does not involve cyclic structures, introduced into the backbone. 

The base for our polymeric initiators are amino functionalized poly(organosiloxane)s with different amino content and a molecular weight of about 15.000 g mol". These structures can be modified with azo or triazene groups according to Fig. 1 and 2. 

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. 

Precrosslinked poly(organosiloxane) particles are synthesized (Scheme 2) by emulsion polycondensation/polymerization of (functionalized) alkoxysilanes and (optionally) cyclic siloxanes [6, 7]. 

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