Disiloxane equilibration polymerization

The oligomers utilized in this study to date have been prepared by the equilibration polymerization of a cyclic tetramer in the presence of functional disiloxanes utilizing a... 

Poly(carboxyalkyl methyl siloxane) and octamethyl cyclo tetrasiloxane are mixed in a monomer ratio of 1 6, hexa methyl disiloxane is added to bring the polymerization degree of the ensuing silicone to about 60, and 6 volume percent of concentrated sulfuric acid are used as equilibration catalyst. 

Siloxane-containing block copolymers are often prepared by step-growth or condensation polymerization of preformed diftmctionalized siloxane oligomers with other diftmctionalized monomers or oligomers. Our current work (3, 4, 6-8) on siloxane chemistry includes the preparation of a number of functionalized oligomers, with emphasis on equilibration processes with the commonly available cyclic tetramer, octamethylcyclotetrasiloxane (D4), in the presence of a functionalized disiloxane or end blocker. 

Silicone oils. These are formed when the crude hydrolysis product mentioned above is made to undergo further polymerization using acid or alkali as catalyst. In this equilibration process the hydroxy-ended oligomers condense with elimination of water, and the cyclic oligomers open and also produce long chain polymers. The average chain length is determined by the addition of exactly controlled amounts of hexamethyl-disiloxane ... 

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