MESOMORPHIC CYCLOLINEAR ORGANOSILOXANE AND ORGANOCARBOSILOXANE BLOCK-COPOLYMERS

Cyclolinear organosiloxane and organocarbosiloxane block copolymers ha ve been obtained by a heterofunctional condensation reaction of ega-[d ioxy(decaorganocyclohexasiloxane-2,8-diyls)] with alpha,omega-dichloro polydimethylsiloxanes and bis-(chlorodimethylsilyl)alkanes. DSC, X-ray , and thermooptical analyses show that nearly all of the synthesized p olymers exhibit at least two phase transitions, from mesophase 1 to me sophase 2 and from mesophase 2 to isotropic melt. The isotropization t emperature of block copolymers decreases monotonically when the length of the siloxane spacer increases. The dependence of this temperature on the length of carbosiloxane fragment is of an even-odd type. It is established that both the low temperature mesophase 1 and the high tem perature mesophase 2 are strongly ordered and inherit the properties o f the homopolymers.