Silicon-Containing Polyphilic Bent-Core Molecules: The Importance of Nanosegregation for the Development of Chirality and Polar Order in Liquid Crystalline Phases Formed by Achiral Molecules
作者:Christina Keith、R. Amaranatha Reddy、Anton Hauser、Ute Baumeister、Carsten Tschierske
DOI:10.1021/ja057685t
日期:2006.3.1
increasing length of the alkyl chains, segregation is lost and a transition from smectic to a columnar phase is found. In the columnar phase, the switching process is antiferroelectric and takes place by rotation of the molecules around the long axes, which reverses the layer chirality; that is, the racemic ground-state structure is switched into a homogeneous chiral structure upon application of an
合成了由弯曲的芳香核、低聚(硅氧烷)单元和烷基链段组成的多亲分子,并研究了这些分子的自组织。大多数材料组织成极性近晶液晶相。这些中间相的转换过程从非甲硅烷化化合物的反铁电通过超顺电转变为表面稳定的铁电,随着甲硅烷化链段的分离增加。提出硅氧烷亚层稳定极性向斜铁电(SmC(s)P(F))结构,并且从宏观极性顺序以及空间效应的逃逸导致层变形,形成无序微畴,产生光学各向同性。另一个显着特征是具有相反旋向性的手性域的自发形成。对于两种化合物,发现这些域的旋光度随温度而变化,这与分子倾角从 < 45 度增加到 > 50 度有关。这一观察证实了最近提出的层光学手性概念(Hough, LE; Clark, NA Phys. Rev. Lett. 2005, 95, 107802),这是超分子系统中光学活动的新来源。随着烷基链长度的增加,偏析消失并且发现从近晶相到柱状相的转变。在柱状相中,转换过程是反铁电的