Design of liquid crystals with ‘de Vries-like’ properties: carbosilane-terminated 5-phenylpyrimidine mesogens suitable for chevron-free FLC formulations
Design of liquid crystals with ‘de Vries-like’ properties: carbosilane-terminated 5-phenylpyrimidine mesogens suitable for chevron-free FLC formulations
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具有类似“de Vries”特性的液晶设计：适合无 V 形 FLC 配方的碳硅烷封端 5-苯基嘧啶介晶
DOI：
10.1039/c4tc00393d
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发表时间：
2014
影响因子：
6.4
通讯作者：
R. P. Lemieux
中科院分区：
文献类型：
--
作者：
C. P. J. Schubert;A. Bogner;J. H. Porada;K. Ayub;T. Andrea;F. Giesselmann;R. P. Lemieux
具有De Vries类性质的近晶液晶的最大层收缩在从正交形状记忆合金相转变到倾斜形状形状记忆合金相时达到≤1%。为了扩大制备不含人字形铁电液晶混合物所需的“类De Vries”液晶库，我们报道了用改进的合成路线合成了一系列同源的三碳硅烷5-苯基嘧啶类液晶QL16-n，并表征了它们的液晶和“类De Vries”性质。用单区二维X射线散射测量取向有序参数S2和有效分子长度Leff表明，QL16-n系列的“类De Vries”行为是由于S2的增加和双层交错的减少共同作用的结果，从而导致近晶层的膨胀，补偿了SMC相的分子倾斜。我们还展示了如何通过将三碳硅烷端基缩短为二碳硅烷来优化SMC相的光学倾斜角，以用于SSFLC显示器--而不会影响De Vries类特性。本文报道的两种新材料，5-[4-(12，12，14，14，16，16-hexamethyl-12，14，16-trisilaheptadecyloxy)phenyl]-2-hexyloxypyrimidine(QL16-6)和2-hexyloxy-5-[4-(12，12，14，14-tetramethyl-12，14-disilapentadecyloxy)phenyl]pyrimidine(QL24-6)是迄今报道的最好的类De Vries材料之一，其宽广的SMC相和还原因子R分别为0.17和0.18，在降温温度T−Tac=−10K下，我们还表明，在同系系列QL17-n中5-苯基嘧啶核的取向颠倒会导致‘de Vries-like’性质的抑制。这些结果表明，由这些介元形成的插层近晶双层中的非共价核-核相互作用可能影响类De Vries行为。
Smectic liquid crystals with ‘de Vries-like’ properties are characterized by a maximum layer contraction of ≤1% upon transition from the orthogonal SmA phase to the tilted SmC phase. In an effort to expand the library of ‘de Vries-like’ liquid crystals required for the formulation of chevron-free ferroelectric liquid crystal mixtures, we report the synthesis of a homologous series of tricarbosilane 5-phenylpyrimidine liquid crystals QL16-n using an improved synthetic route, and the characterization of their liquid crystalline and ‘de Vries-like’ properties. Measurements of orientational order parameters S2 and effective molecular lengths Leff by monodomain 2D X-ray scattering suggest that ‘de Vries-like’ behavior in series QL16-n is due to the combined effect of an increase in S2 and a decrease in bilayer interdigitation, thus causing a smectic layer expansion that compensates for the molecular tilt in the SmC phase. We also show how the optical tilt angle in the SmC phase may be optimized for SSFLC displays—without compromising ‘de Vries-like’ properties—by shortening the tricarbosilane end-group to a dicarbosilane. Two of the new materials reported herein, 5-[4-(12,12,14,14,16,16-hexamethyl-12,14,16-trisilaheptadecyloxy)phenyl]-2-hexyloxypyrimidine (QL16-6) and 2-hexyloxy-5-[4-(12,12,14,14-tetramethyl-12,14-disilapentadecyloxy)phenyl]pyrimidine (QL24-6) rank among the best ‘de Vries-like’ materials reported heretofore, with broad SmC phases and reduction factors R of 0.17 and 0.18, respectively, at a reduced temperature T − TAC = −10 K. We also show that inverting the orientation of the 5-phenylpyrimidine core in the homologous series QL17-n causes a suppression of ‘de Vries-like’ properties. These results suggest that non-covalent core–core interactions in the intercalated smectic bilayers formed by these mesogens may influence ‘de Vries-like’ behavior.
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DOI：
10.1063/1.1943972
发表时间：
2005
期刊：
The Journal of chemical physics
影响因子：
--
作者：
F. Giesselmann;R. Germer;A. Saipa
通讯作者：
A. Saipa
直接观察有机硅氧烷介晶 de Vries 近晶 A 相和 C 相中的扩散锥体行为。
影响因子：
8.6
作者：
H. Yoon;D. M. Agra;K. Ayub;R. Lemieux;Satyendra Kumar
通讯作者：
Satyendra Kumar
X 射线衍射测量的三种液晶的分布函数
DOI：
--
发表时间：
1979
期刊：
影响因子：
--
作者：
A. Leadbetter;E. Norris
通讯作者：
E. Norris
影响因子：
8.6
作者：
J. Naciri;J. Ruth;G. Crawford;R. Shashidhar;B. Ratna
通讯作者：
B. Ratna
具有电动性质的含硫靛的有机硅氧烷液晶
影响因子：
--
作者：
J. Vlahakis;K. Maly;R. Lemieux
通讯作者：
R. Lemieux