Dimethylsiloxane cyclic trimer

Hexamethylcyclotrisiloxane Dimethylsiloxane cyclic trimer CeFli8 3Si3 641-06-9 222.462 64.6 134 1.12002" i HjO... 

Yamashita et al. obtained polydimethyl siloxane macromer through polymerization of dimethylsiloxane cyclic trimer, initiated by trimethyl siloxy lithium. The reaction was terminated by compounds containing both chlorine and vinyl groups, to obtain the desired macromer. 

Controlled synthesis and detailed characterization of triblock copolymers of di-phenylsiloxane and dimethylsiloxane has been reported by Meier and co-workers147 148), who used lithium based initiators and the cyclic trimers of dimethyl and diphenyl-... 

The synthesis of poly(dimethylsiloxane)macromonomers was also carried out anionically. The cyclic trimer D3 of dimethylsiloxane may be polymerized anionically, using lithium trimethylsilanolate as the initiator. Deactivation of the silanolate end groups may be performed with chlorosilyl functions. Yamashita et al. 29) successfully applied the unsaturated deactivators I and II... 

The evidence is strengthened by the preparation from the cyclic trimer or tetramer of the related linear compounds (PNCUin PCI-, (Section II, C), which have quite different properties. The stable existence of such large rings has in any case seemed less unreasonable since the isolation of the separate members of the cyclic dimethylsiloxane series (Me2SiO) up to the nonamer, which has a 18-membered ring (see p. 80 in ref. 65). 

An intensive investigation has been made of the thermal degradation of poly(dimethylsiloxane) and poly(methylphenylsiloxane). " The main products are a mix of all the possible stereoisomeric cyclic trimers and tetramers together with small amounts of pentamer and cyclic oligomers. In the degradation of poly(dimethylsiloxane) fluids, however, significant amounts of linear products are... 

Cyclic trimer and tetramer of dimethylsiloxane and a complex mixture... 

There is an interesting analogy between cyclosiloxanes and the cyclic metasilicates [Si 03 ] " n = 3-6), e.g. (Me2SiO)3 (10.42) and [SisOg] " (10.43) the methyl groups in the dimethylsiloxanes are replaced by the formally iso-electronic in the silicates. Cyclic metasilicates occur naturally in certain minerals. For example, the trimer (n = 3) is found in CasSisOg (a-wollastonite), whereas the hexamer (n = 6) is a constituent of Be3Al2Si60ig (beryl). 

An understanding of the thermodynamics of ring-chain equilibration reactions is important in Inorganic Chemistry where such reactions abound (sse, for example. Allcock (65), Gee (66), Gimblett (67), and Moedritzer (65)). Two such reactions are found (i) in polyphosphazene chemistry (69) where a polymerisation-depolymerisation equilibrium can be established (70) and (ii) in silicon-sulphur chemistry, where the analogue of the poly(dimethylsiloxane) system has been studied (71) and shown to contain cyclics such as the dimer ( (013)2 SiS)2 the trimer ((CH3)2SiS)3, as well as small amounts of chain molecules of limited chain length. 

Anionic Ring Opening Polymerization of Cyclic Dimethylsiloxanes (A) Promoted Organolithium/Trimer Reactions... 

Silicones have been claimed to improve combing, enhance feel, reduce flyaway, increase shine, reduce drying time, and lock in color [54-56], The most frequently used silicone is dimethicone, which is a polydimethylsiloxane. Other important silicones are dimethiconol, which is a dimethylsiloxane terminated with hydroxyl groups, amodimethicone, which is an amino-substituted silicone, dimethicone copolyol, which is a dimethylsiloxane containing polyoxyethylene and/or propylene side chains, and cyclomethicone, which refers to a class of cyclic dimethyl polysiloxanes ranging from trimer to hexamer ... 

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