Cyclotrisiloxanes

Monomer Production. The key industrial monomer is 2,4,6-trimethyl-2,4,6-tris-(3,3,3-trifluoropropyl)cyclotrisiloxane [2374-14-3] which is produced by the hydrosilylation of 3,3,3-trifluoropropene [677-21-4] with methyldichlorosilane [75-54-7] cataly2ed by various platinum and other noble metal compounds (eq. 3). 

Preparation of other fluorosilicone monomers follows methods similar to that described above. For example, 2,4,6-trimethyl-2,4,6-tris(3,3,4,4,5,5,6,6,6-nona- uorohexyl)cyclotrisiloxane [38521-58-3] is produced from 3,3,4,4,5,5,6,6,6-nona-fluorohexene [19430-93 ] and methyldichlorosilane in three steps (3). 

An alternative procedure involved the coupling of polysilanolate, obtained by sequential addition of cyclotrisiloxane to the polystyrene anion, with a, co-diacetoxy-siloxane385-386- 399>. 

Anionic polymerization in suitable systems allows the preparation of polymers with controlled molecular weight, narrow molecular weight distributions and functional termination. The functional termination of a living anionic polymerization with a polymerizable group has been used frequently in the preparation of macromonomers (4). Our research has encompassed the anionic homo and block copolymerizations of D- or hexamethyl cyclotrisiloxane with organolithiums to prepare well defined polymers. As early as 1962 PSX macromonomers were reported in the literature by Greber (5) but the copolymerization of these macromonomers did not become accepted technique until their value was demonstrated by Milkovich and... 

Polysiloxanes (l)-(4) bearing phenyldisilanyl units could be readily prepared by copolymerization of 1,3,5-triphenyl[tris(trimethylsilyl) ]cyclotrisiloxane and cyclopolysiloxanes in the presence of a catalytic amount of an intercalation compound prepared from graphite and potassium metal in a ratio of 8 1, in high yields. 

Figure 12.14 Pyrogram of the silicone coating from Mello s Tavolo erba. Peak assignments I, hexamethyi cyclotrisiloxane 2, octamethyl cyclotetrasiloxane 3, decamethyl cyiclopenta siloxane 4, dodecamethyl cyclohexasiloxane 5, tetradecamethyl cyclooctasiloxane...

Cyclotriphosphazene hosts, 14 177-178 Cyclotrisiloxanes, 20 242 Cyclotriveratrylenes, 14 178 24 37 organometallic derivatives of, 24 44-45 Cycopac, composition, 3 386t Cylinder oil, 15 594 Cylinder paper former, 15 118—119 Cylinders, flows around, 11 753-757 15 720t... 

Chojnowski, J. Kazmierski, K. Cypryk, M. Fortuniak, W. Cationic Ring Opening Polymerization of Cyclotrisiloxanes with Mixed Siloxane Units. In Silicones and Silicone-Modified Materials-, Clarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Eds. ACS Symposium Series 729 American Chemical Society Washington, DC, 2000 pp 20-37. 

The lithiated aminofluorosilane f-Bu2Si—N—Si(OSiMc3)Pr-/2 FiF 2 809 behaves in the same way, and its cycloadduct with benzaldehyde decomposes into the respective imine and cyclotrisiloxane above 105 °C354. 

When a toluene solution of a mixture of cyclotrisilane 34 and cyclohexyl isocyanate (or f-butyl isocyante) was heated at 70 °C, cyclic di- and trisiloxanes 37 and 38, i.e. the cyclic dimer and trimer of the silanone 36, were obtained together with the corresponding isonitrile RN=C. The formation of 37 as well as 38 was completely suppressed in the presence of hexamethylcyclotrisiloxane (19 D3) instead, quantitative conversion of 35 into 39, the formal insertion product of the silanone 36 into the Si—O bond of D3, occurred (Scheme 14). Since neither cyclodisiloxane 37 nor cyclotrisiloxane 38 reacted with D3 under the reaction conditions, the possibility that 37 or 38 is the precursor of 39 was ruled out. Whereas the oxidation of 35 with cyclohexyl and t-butyl isocyanates proceeded with exclusive formation of 37 and 38 (as the silicon-containing compounds) the reaction of 35 with phenyl isocyanate resulted in the formation of 37 in low yield. Furthermore, in this case the presence of D3 did not totally suppress the formation of 37. According to the authors, these results indicate that the oxidation of 35 with cyclohexyl and f-butyl isocyanates appears to use other reaction channels than that with phenyl isocyanate. 

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