cis-Tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes: Synthesis and mesomorphic propertiesстатья
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Дата последнего поиска статьи во внешних источниках: 18 марта 2017 г.
Аннотация:Hydrolytic condensation of organotrialkoxysilanes RSi(OR′)3 (R = Me, Et, Pr, CH=CH2; R′ = OMe, OEt) in the presence of sodium and/or potassium hydroxide gave new alkali organosiloxanolates {(M+)4[RSi(O)O−]4}·nL (R = Me, Et, Pr, CH=CH2; M = Na, K; L = R′OH, H2O) in which the main structural fragment is the cyclotetrasiloxanolate fragment cis-[RSi(O)O−]4. Based on these organosiloxanolates, a series of cis-tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes was synthesized. For new cyclotetrasiloxanes, the thermotropic transitions and mesomorphic orderings were determined by differential scanning calorimetry, X-ray diffraction analysis, and polarization microscopy. In addition, new mesomorphic compounds were revealed. The character of thermotropic and time evolution of the phase state was found for a mixture of cis-tetra[ethyl(trimethylsiloxy)]-and cis-tetra[phenyl(trimethylsiloxy)]cyclotetrasiloxanes.