COMBINED LC MAIN-CHAIN SIDE-CHAIN POLYMERS

Combined LC-polymers possess the structural properties of both LC main chain and LC side chain polymers. Beneath this structural speciality, their broad LC-phases and their polymorphism (different smectic phase s and one nematic phase as a function of temperature) make them intere sting. Crucial to an understanding of them is the fact that main chain and side chain mesogens orient parallel to each other and interact co operatively to form the LC-phase. Due to this synergism the temperatur e range of the LC-phase is much broader than that of the corresponding LC main chain and LC side chain poly polymers. This interplay of main chain and side chain mesogens allows structures to be designed with p referably nematic or smectic phases. Whenever both types of mesogens c an arrange in the same height, preferably smectic phases are formed. I f this is not possible, the nematic phase dominates. The incorporation of chiral groups allows cholesteric and chiral smectic C phases to b e prepared. For the latter, ferroelectric modes have been observed die lectrically. By crosslinking of combined LC-polymers, combined LC-elas tomers can be prepared, in which the LC-phases are nearly unchanged. T hese elastomers allow a mechanical orientation of the LC-phases and, i n particular, an untwisting of the helical superstructure of cholester ic and chiral smectic C phases. In the latter case ferroelectric mono domains are obtained. The piezoeffect - to be expected - for LC-elasto mers with chiral smectic C phases was first demonstrated for this cla ss of polymers.