Viscoelasticity, dielectric anisotropy, and birefringence in the nematic phase of three four-ring bent-core liquid crystals with an L-shaped molecular frame
摘要:
分子形状是决定热致液晶(LC)材料性质的重要因素。我们合成并研究了几种由不对称弯曲分子构成的液晶化合物,这些分子具有一个形状像字母“L”的刚性四环核心。我们测量了介电常数、双折射、撓曲 K1 和弯曲 K3 弹性常数、撕裂粘度 ηsplay 以及流动粘度 η|| 和 η⊥ 的温度依赖性。弯曲-撕裂各向异性 δK31 = K3 − K1 为负,类似于由对称弯曲的 V 形分子形成的向列型液晶的情况。介电各向异性 Δε 和双折射在整个向列相范围内均为正。撕裂粘度 ηsplay 和流动粘度 η|| 及 η⊥ 小于在类似温度下测得的对称 V 形弯曲核心材料的粘度。比率 Γ = ηsplay/η||,⊥ 在 5-4 范围内,这是典型的杆状液晶的特征。报道的 L 形弯曲核心向列型液晶结合了弯曲核心液晶的有用特征(例如负的 δK31,适合于广范围蓝相的形成)与相对较低的粘度,这是杆状液晶的典型特性,对于电光开关应用具有益处。
the concentration of sulfuricacid. Treatment of 4-haloazoxybenzenes with sulfuricacid gave 4-(p-halophenylazo)phenols and 4-haloazobenzenes (13) as major products together with 2-(p-halophenylazo)phenols and 5-halo-2-(phenylazo)phenols as minor products. Yields of reduction products 6 and 13 increased as the halosubstituent became heavier in the following sequence: F→Cl→Br→I.
Dinuclear ortho-metallated palladium(II) azobenzene complexes with acetato and chloro bridges: Influence of polar substituents on the mesomorphic properties
作者:Trirup Dutta Choudhury、Yongqiang Shen、Nandiraju V.S. Rao、Noel A. Clark
DOI:10.1016/j.jorganchem.2012.04.001
日期:2012.8
The synthesis, characterization and mesomorphicproperties of a new series of acetate and chloro-bridged dinuclear orthopalladated complexes derived from azobenzene with terminal groups of hexadecyloxy moiety at one end and different polar groups (Me, Cl, F, NO2, CN) at the other end are described. The mesomorphicproperties of both the ligands and complexes were investigated by polarizing optical
New Generation of Nitrite Functionalized Star-like Polyvinyl Imidazolium Compound: Application as a Nitrosonium Source and Three Dimensional Nanocatalyst for the Synthesis of Azo Dyes
Background: The compounds with three-dimensional and ionic structures have attracted
considerable attentions because of their unique characteristics as a drug carrier and catalyst. Star-like
poly ionic compounds are a new generation of three-dimensional structures which have both; the exclusive
ionic features and three-dimensional structures. Recently, we reported the synthesis of diazonium
salts from aniline derivatives using carboxyl and nitrite functionalized graphene quantum dots.
Methods: Nitrite-functionalized star-like polyionic (NFSP) compound was synthesized as a new generation
of three-dimensional nanocatalyst. Herein, the use of NFSP as an efficient reagent and nanocatalyst
for the diazotization of aniline derivatives and subsequent synthesis of azo dyes via the reaction
with active phenolates under solvent-free conditions was reported.
Results: In order to demonstrate the positive impact of NFSP efficiency, the reaction times and yields
of the products were compared with other methods and catalysts which have been reported previously.
The brilliant performance of NFSP can be ascribed to multifunctional reagent and also trapping the ingredient
within catalyst cavities.
Conclusion: A highly effective and cost-effective method has been developed for the preparation of
azo dyes. In reported method, new three-dimensional catalyst with highly ionic characteristic and multifunctional
nitrosonium source is available. These special features reduced the required amount of
catalyst, reaction time and also increased the efficiency of catalyst.
synthesis of photoactive comb‐shaped homo‐ and copolyamides containing azobenzene, cinnamate, and coumarin side groups for photoalignment of liquidcrystals was elaborated. Photooptical properties and photoorientational ability of these polymers with respect to liquidcrystals were studied. It was shown that polarized UV irradiation of all spin‐coated polyamides leads to orientation of liquid crystalline