摘要 : Novel liquid crystalline materials with fluorinated biphenyl-based bent aromatic cores have been synthesized. The influence of fluorine substitution at the aromatic core and the effects of combining oligosiloxane units and fluorin... 展开 Novel liquid crystalline materials with fluorinated biphenyl-based bent aromatic cores have been synthesized. The influence of fluorine substitution at the aromatic core and the effects of combining oligosiloxane units and fluorine substitution were studied. The mesophases were investigated by polarizing microscopy, calorimetry, X-ray diffraction, and electrooptical investigations. Different types of polar smectic and columnar phases were observed. Depending on the position of the F substituents antiferroelectric and surface-stabilized ferroelectric switching subtypes of optically isotropic smectic phases composed of domains with opposite chirality sense (dark conglomerate phases) were obtained. All columnar phases represent ribbon phases with an oblique lattice. One type of columnar phase shows ferroelectric switching (Col(ob)P(FE)), and the other shows antiferroelectric switching (Col(ob)P(A)) which changes to a "nonclassical" antiferroelectric switching at reduced temperature. During the switching process the molecules reorganize by rotation on a cone in the Col(ob)P(FE) phase and by rotation around the molecular long axis in the antiferroelectric columnar phase. The switching around the long axis is of special interest as it changes the suprastructural chirality of the LC system. Development of phase structures and switching behavior is discussed with respect to the influences of internal and external interfaces. 收起