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.
Chiral 4-cyanoresorcinol derived bent-core molecules form liquid crystalline phases with helically deformed layers representing TGBA and TGBC-like structures.
手性4-氰基间苯二酚衍生的弯曲核分子形成液晶相,具有螺旋变形层,代表TGBA和TGBC类似的结构。
Effects of chain branching and chirality on liquid crystalline phases of bent-core molecules: blue phases, de Vries transitions and switching of diastereomeric states
作者:Hale Ocak、Belkız Bilgin-Eran、Marko Prehm、Stefan Schymura、Jan P. F. Lagerwall、Carsten Tschierske
DOI:10.1039/c1sm05826f
日期:——
microscopy, X-ray diffraction, electro-optic and dielectric methods. Only bent-coremesogens derived from 4-cyanoresorcinol exhibit liquid crystalline phases and the mesophases of these compounds are strongly influenced by the branching and enantiomeric composition of the terminal chains. Depending on the structure of the rod-like wings and the enantiomeric composition, cybotactic nematic phases (NcybC), BPIII-like
Biphenyl-3,4′-diol derived bent-core compounds with branched side chains have been synthesized and characterized to study the influence of terminal branched groups on mesophase properties and transition temperatures of bent-core mesogens. The liquid crystalline properties of the compounds were investigated by differential scanning calorimetry, optical polarizing microscopy and X-ray scattering. Depending on the length of the chain, the size of molecular branches and the position of branched chains, either enantiotropic or monotropic rectangular columnar phases were observed. For one of the compounds combining two different branched side chains, a new type of optically isotropic dark conglomerate phase (MIso[*]) was found. It is proposed to be a distorted version of a non-tilted or only slightly tilted B6-like intercalated smectic phase with additional in plane order.
我们合成了具有支化侧链的联苯-3,4′-二醇衍生弯曲核化合物,并对其进行了表征,以研究末端支化基团对弯曲核介质的介相性质和转变温度的影响。通过差示扫描量热法、光学偏光显微镜和 X 射线散射法研究了这些化合物的液晶特性。根据分子链的长度、分子分支的大小和分支链的位置,可以观察到各向同性或各向同性的矩形柱状相。对于其中一种结合了两种不同支链侧链的化合物,发现了一种新型光学各向同性暗砾石相(MIso[*])。据推测,它是一种无倾斜或仅有轻微倾斜的 B6 类插层 Smectic 相的扭曲版本,具有额外的平面顺序。
Biphenyl Based Non-symmetrical Bent-Core Mesogens Containing a Chiral Moiety and an Olefinic End Group
作者:Hale Ocak、Belkiz Bilgin-Eran
DOI:10.1080/15421406.2014.953746
日期:2015.3.4
properties of bent-coremesogens. The liquidcrystalline properties of the compounds were investigated by differential scanning calorimetry, optical polarizing microscopy, and electro-optic methods. Depending on the length of the olefinic chain and the number of aromatic rings in the rod-like wings, the bent-core compounds with a chiral moiety show B1 type mesophase, polar smectic C phase (SmCP) or nonmesomorphic