The first examples of polyphilic bent-core compounds consisting of a biphenyl central core, a chiral terminal chain and an oligo(dimethylsiloxane) end group at the other terminus have been synthesized and characterized. The mesomorphic behaviour of the compounds was investigated by differential scanning calorimetry, optical polarizing microscopy, X-ray diffraction and electro-optic methods. The olefinic precursors show monotropic or enantiotropic B1 type mesophases. The siloxane substituted analogues containing a racemic chain exhibit dark conglomerate phases (DC[*] phases) which are composed of chiral domains with opposite chirality, whereas the siloxane derivatives with a homogeneously chiral moiety show “dark enantiomer” phases (DE* phases) with uniform chirality. Under electric fields, different types of ferroelectric switching (FE) smectic and modulated smectic phases were induced. The effects of chain branching, spacer length and molecular chirality on the stability of the DCFE[*] and DEFE* phases and on the field-induced smectic and modulated smectic phases were investigated.
首次合成了由
联苯中心核、手性末端链和寡聚(二甲基
硅氧烷)另一末端组成的多元亲和弯曲核心化合物,并对其进行了表征。通过差示扫描量热法、光学偏振显微镜、X射线衍射和电光方法研究了这些化合物的液晶行为。烯烃前体显示出单稳态或二稳态的B1型中间相。含有消旋链的
硅氧烷取代类似物表现出暗聚集体相(DC[*]相),它们由具有相反手性的手性域组成,而含有均匀手性部分的
硅氧烷衍
生物显示出具有均匀手性的“暗对映体”相(DE*相)。在电场作用下,诱导出不同类型的
铁电开关(FE)层状和调制层状相。研究了链分支、间隔长度和分子手性对DCFE[*]和DEFE*相稳定性的影响,以及对场诱导层状和调制层状相的影响。