Siloxanes organosiloxanes

Silicone polymers such as ethoxylated aryl/organosiloxane polymer and siloxane glycol/PAG copolymer also are used occasionally. 

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... 

Other reports on the morphology and mechanical behavior of organosiloxane containing copolymeric systems include polyurethanes 201 202), aliphatic 185, 86) and aromatic117,195> polyesters, polycarbonates 233 236>, polyhydroxyethers69,311, siloxane zwitterionomers 294 295) and epoxy networks 115>. All of these systems display two phase morphologies and composition dependent mechanical properties, as expected. 

A novel feature of the route is that it leads to monomeric and oligomeric alkyl silicates from metal silicates in good yield and with full or substantial siloxane framework preservation. Further, it leads to oligomeric organosiloxanes of intermediate molecular weight from alkyl silicates in good yield and with siloxane framework preservation. 

Siloxane containing block or segmented copolymers can be synthesized either by living anionic polymerization of the cyclic organosiloxane trimers with appropriate vinyl monomer(, 4 ) or by step-growth or condensation copolymerization of preformed a,w-difunctional siloxane oligomers with conventional difunctional... 

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. 

It is necessary that the silicol condense at a rate comparable to that for orthosilicic acid, since otherwise the latter will condense only with itself and will precipitate as silica before it can be included within the siloxane network. It also is found by experiment that only a rather small proportion of SiX4 may be included in the mixture of intermediates if the precipitation of silica is to be avoided. However, the mere fact that appreciable amounts of silica can be combined chemically within the polysiloxane structure is strong evidence in support of the theory of intermolecular condensation as given here, and at the same time it illustrates the close chemical similarity between silica and the organosiloxanes. 

Organosiloxane. A siloxane in which organic groups are linked directly to one or more of the silicon atoms by carbon-silicon bonds, as in hexamethyl-disiloxane, (CH3)3Si—0—Si(CH3)3. 

Bead-Shaped Organosiloxane Oligomers and Copolymers with Organocyclotetra(Penta, Hexa)Siloxane Fragments... 

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