SIDE-CHAIN LIQUID-CRYSTALLINE POLYMERS CONTAINING SILOXANE SPACER .3. THERMAL-PROPERTIES OF COPOLYMERS CONTAINING DIFFERENT TYPES OF MESOGENS

Copolymerization of monomers containing the disiloxane unit in the spacer component and linear triple-core mesogens with comonomers containing linear double-core mesogens, or laterally attached triple-core mesogens was carried out radically. The effect of copolymer composition and monomer structure on the mesomorphic properties of the obtained copolymers was investigated in detail. The copolymers with a comonomer content up to 50 mol-%, exhibit an enantiotropic nematic phase, whereas the parent homopolymers containing triple-core mesogens exhibit a smectic phase. The copolymer containing more than 50 mol-% of the comonomer shows no mesophase. The isotropization temperature of the copolymers decreases with increasing comonomer content. However, the glass transition temperature is almost unchanged upon introduction of the comonomer unit. In case of copolymers containing laterally attached mesogens, a smectic phase was observed below the temperature range of the nematic phase. Consequently, the mesophase and the temperature range of the liquid-crystalline state can be controlled by the introduction of the comonomer unit whose parent homopolymer does not exhibit any mesophase.