SIDE-CHAIN LIQUID-CRYSTALLINE POLYMERS CONTAINING THE SILOXANE SPACER .5. SYNTHESES AND THERMAL-PROPERTIES OF COPOLYMETHACRYLATES WITH DIFFERENT SPACER STRUCTURES

Copolymerizations of the methacrylate-type monomers whose spacer consisted of only alkylene unit with the comonomers containing a disiloxane unit in the spacer component were carried out by radical polymerization. The effects of copolymer composition and structure of mesogen on the mesomorphic properties of the obtained copolymers were investigated, using DSC, optical polarizing microscope and X-ray diffractometry. T(g) and T(i) of the copolymers decreased with increase in comonomer component reflecting the flexibility of the siloxane linkage. The introduction of the comonomer containing a siloxane spacer and a laterally attached mesogen was effective to lower the temperature range of the mesophase. The copolymers, of which the comonomer content was about 50 mol%, exhibited an enantiotropic nematic phase, whereas the parent homopolymers exhibited a smectic phase. Consequently, the mesophase and temperature range of liquid crystalline state could be controlled by the introduction of a comonomer unit containing a siloxane spacer.