FORMATION OF THERMOTROPIC MESOPHASES IN C YCLOLINEAR ORGANOSILOXANE HOMOPOLYMER AND COPOLYMER BEARING HEXAALKYLCYCLOTETRASILOXANE FRAGMENTS

The copolymers bearing alkyl substituents at silicon atoms (Me, Et) an d varying by the length of dialkylsiloxane spacer m were synthesized b y heterofunctional polycondensation of ,6-dioxy-2,4,4,6,8,8-hexaalklyl cyclotetrasiloxanes with alpha,omega-dichloropolydialkylsiloxanes. The majority of trans tactic copolymers with methyl substituents (m = 1, 3, 4) are amorphous compounds, except far a crystallizable copolymer w ith m = 2. The mesomorphic state was discovered for noncrystallizable atactic copolymers with ethyl substituents containing not more than tw o diethylsiloxane units (m = 1, 2); as m increases to 3, the ability t o form ordered structures is suppressed. Comparative study of the stru ctural characteristics of the mesophase of the copolymers and hexaalky lcyclotetrasiloxane homopolymers in a wide temperature range was perfo rmed by X-ray diffraction analysis. It was established that homo- and copolymers have identical types of ordering in the mesophase, and the parameters of pseudohexagonal packing were determined.