TEMPERATURE-MEDIATED EVOLUTION OF PHASE-C OMPOSITION IN MESOMORPHIC ALTERNATING CYCLOLINEAR ORGANOSILOXANE COPOLYMERS WITH DIFFERENT SPATIAL ALIGNMENT OF ORGANOSILSESQUIOXANE ELEMENTS IN THE CHAIN

Alternating cyclolinear organosiloxane copolymers comprising hexamethy lcyclotetrasiloxane and decamethylcyclohexasiloxane fragments of vario us tacticities were prepared by heterofunctional condensation of trans -2,6-dichlorohexamethylcyclotetrasiloxane with trans- or cis-2,8-dioxy decaniethylcyclohexasiloxanes. Stereoregularity of the copolymers was verified with Si-29 NMR spectroscopy. Using DSC and X-ray diffraction analysis, it was demonstrated that the synthesized copolymers were mes omorphic; the order manifested in the mesophase was determined by the homopolymer - poly[oxy(decamethylcyclohexasiloxane-2,8-diyl)]. The tem perature dependences of both the phase state and the structural charac teristics of the mesophase were controlled by the tacticity of the mai n chain. For the copolymers, a pronounced solidification of the mesoph ase was observed; this effect was not observed in mesomorphic poly[oxy (decamethylcyclohexasiloxane-2,8-diyl)] of different tacticities.