SYNTHESIS, PHASE-TRANSITIONS, AND MESOMORPHIC STATE IN TRANSTACTIC CYCLOLINEAR ORGANOSILOXANE COPOLYMERS

Transtactic cyclolinear organosiloxane copolymers were obtained by het erofunctional condensation reaction of trans-2,8-dioxydecaorganocycloh exasiloxanes with alpha,omega-dichloropolydimethylsiloxanes or bis-(ch lorodimethylsilyl)alkanes. The structure of the synthesized products i s confirmed by 1H and Si-29 NMR spectra and by chemical analysis. By u sing DSC, X-ray and thermooptical analyses it is shown that transtacti c copolymers exhibit high crystallinity, regardless of the nature of o rganic substituents in the organosilsesquioxane fragment of cyclohexas iloxane. Above the melting point one of the copolymers is in a mesomor phic state and reveals a two-stage transition from mesophase to the is otropic melt.