Rigid Phenylene Ethynylene Units Linked by A V-shaped Centre. An Approach to Biaxial Nematogens?
作者:Matthias Lehmann、Jérémy Levin
DOI:10.1080/15421400490435260
日期:2004.1
theoretical predictions that nematic phases formed from V-shaped compounds could be biaxial, shape-persistent phenylene ethynylene arms linked by 1,3-phenylene, 4,4′-diphenylenemethane and 3,6-fluorenone units have been synthesised. Crystallisation and micro-segregation is prevented by 2,5-alkoxy substitution on the middle benzene ring of the arms. The specific molecular engineering, i.e. variation
A series of biaxial V-shaped, shape-persistent molecules has been synthesised by stepwise coupling of phenylene ethynylene arms to an oxadiazole bending unit. Studies of their thermotropic nematic phases point to phase biaxiality.
Synthesis and mesomorphic properties of new V-shaped shape-persistent nematogens containing a thiazole or a thiadiazole bending unit
作者:Matthias Lehmann、Jens Seltmann、Alexander A. Auer、Eric Prochnow、Udo Benedikt
DOI:10.1039/b818240j
日期:——
Two series of new V-shaped molecules, containing a central thiazole or thiadiazole bending unit have been synthesised. The design is based on shape-persistent phenylene ethynylene scaffolds that were attached stepwise with high regioselectivity to a desymmetrised iodo and bromo functionalised bent core with an apex angle of about 160°. Molecular engineering results in materials that exhibit exclusively nematic liquid crystal phases (monotropic or enantiotropic). The phase behaviour was investigated by means of polarised optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction.
我们合成了两个系列的新型 V 形分子,其中包含一个中央噻唑或噻二唑弯曲单元。这种设计基于形状持久的苯乙炔支架,这些支架以高区域选择性逐步连接到顶角约为 160°的非对称碘和溴官能化弯曲核心。分子工程的结果是,材料完全呈现向列液晶相(单向或对映)。通过偏振光学显微镜(POM)、差示扫描量热法(DSC)和 X 射线衍射法对相行为进行了研究。