摘要 : A new homologous series of achiral five-ring bent-core mesogens is presented. The mesophase behaviour has been studied by polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical measurements... 展开 A new homologous series of achiral five-ring bent-core mesogens is presented. The mesophase behaviour has been studied by polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical measurements. The homologues with shorter terminal chains (C-8, C-12) form an SmCPA phase, homologues with longer chains (C-14, C-16, C-18) show liquid-crystalline tetramorphism with a sequence SmA-SmCSPA-Col(ob)-SmCSPA. The SmCPA phases are structurally identical and differ only in the mechanism of polar switching. The switching of the high-temperature SmCSPA phase takes place through the collective rotation of the molecules around their long axes whereas in the reentrant SmCSPA phase the switching is based on the director rotation around the tilt cone. By the application of an electric field the Colob phase can be irreversibly transformed to an SmCPA phase. In a limited temperature range the SmA phase shows a reversible field-induced transition into the SmCSPF phase. The electro-optical response of the mesophases is discussed on the basis of the structural features of these phases. 收起