3, 3, 3-Trifluoropropyl(methyl)cyclosiloxanes |
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Authors: | E G Kagan Yu A Yuzhelevskii V N Frolov A L Klebanskii O N Larionova |
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Institution: | (1) Lebedev All-Union Scientific Institute for Synthetic Rubber, Leningrad |
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Abstract: | The catalytic rearrangement of the cyclopentasiloxanes mD5-m, where represents a 3, 3, 3-trifluoropropyl(methyl)siloxane link and D a dimethylsiloxane link, and m=2–5 has been studied by the method described previously 1]. The rate of rearrangement and the rate of formation of a linear polysiloxane rise with an increase in m from 2 to 4. The equilibrium concentration of the linear polysiloxane formed from mD5-m and from mD4-m (m=0–4) 1] is inversely proportional to the molar fraction of links in the ring and rises with an increase in the total concentration of siloxane links in solution. Results have been obtained on the kinetics of the formation of the cyclosiloxanes mDn (where m=0–5, n=0–5, and m+n=3-6) during the rearrangement of the cyclopentasiloxanes mD5-m. It has been established that at equilibrium a mixture of cyclosiloxanes mDn containing practically constant ratios of tetramers, pentamers, and hexamers (m+n=4, 5, and 6) is obtained, regardless of the composition and structure of the initial cyclosiloxane and of the conditions of rearrangement (polymerization). The cyclopentasiloxanes mD5-m are less active in the process of rearrangement than the cyclotetrasiloxanes mD4-m. The activity of the cyclosiloxanes in rearrangement in the presence of a base rises in the sequence D4D3 2D3<3D2<4D < 2D2 < 3D.For part II, see 1]. |
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