13C–1H dipolar couplings for probing rod-like hydrogen bonded mesogens
作者:M. Kesava Reddy、K. Subramanyam Reddy、T. Narasimhaswamy、Bibhuti B. Das、Nitin P. Lobo、K. V. Ramanathan
DOI:10.1039/c3nj00271c
日期:——
existence of hydrogen bonding between the pyridyl unit and the carboxylic acid was established using FT-IR spectroscopy from the observation of characteristic stretching vibrations of unionized type at 2425 and 1927 cm−1. The mesogenic acceptor and the complex have been investigated using 13C NMR in solution, solid and liquid crystalline states. Together with the 2D separated local field NMR experiments
氢键是用于构建超分子组装体中最重要的非共价相互作用,并且通常优选作为构造具有液晶特性的分子,低聚物以及聚合物材料的手段。在这项工作中,已经合成了基于吡啶的杀线虫受体并将其与非杀霉菌素混合4-甲氧基苯甲酸得到氢键的液晶元。通过在2425和1927cm -1处观察到的联合类型的特征拉伸振动,使用FT-IR光谱法确定了吡啶基单元和羧酸之间的氢键的存在。用溶液,固态和液晶态的13 C NMR研究了介晶受体和配合物。与二维分离局部场NMR实验一起,研究证实了中间相的分子结构并产生了局部取向顺序参数。据观察,插入4-甲氧基苯甲酸 由于氢键合液晶元的核心长度的增加,不仅增强了中间相的稳定性,而且还诱发了近晶相。
Phase Characterization and Study of Molecular Order of a Three-Ring Mesogen by <sup>13</sup>C NMR in Smectic C and Nematic Phases
作者:S. Kalaivani、T. Narasimhaswamy、Bibhuti B. Das、Nitin P. Lobo、K.V. Ramanathan
DOI:10.1021/jp203388v
日期:2011.10.13
noticed for lower homologues, while an additional smectic C phase was found for higher homologues. Solid-state high-resolution natural abundance 13C NMR studies of a typical mesogen in the solid phase and in the mesophases have been carried out. The 13C NMR spectrum of the mesogen in the smectic C and nematicphases indicated spontaneous alignment of the molecule in the magnetic field. By utilizing the
由于其对诸如温度,机械力以及电场和磁场之类的外部刺激的敏感性,表现出热致液晶性质的分子已经变得非常重要。结果,通过在芳族核附近以及在侧链中引入各种官能团,已经合成了几种新颖的介晶,并且已经研究了它们的性质。在本研究中,我们报告了在一个末端带有羟基的三环液晶元。这些介晶通过多步路线合成,并通过光谱技术完成结构表征。通过热阶段光学偏振显微镜,差示扫描量热法和小角X射线散射研究了中间相性质。较低的同系物发现了对映向列相,而较高的同系物则发现了另外的近晶C相。固态高分辨率自然丰度已经对固相和中间相中典型的液晶元进行了13 C NMR研究。层列碳相和向列相的液晶元的13 C NMR光谱表明该分子在磁场中自发排列。通过利用称为SAMPI4的二维分离局部场(SLF)NMR实验,获得了13 C– 1 H偶极耦合,这些耦合用于确定液晶元的取向顺序参数。
The effects of molecular structure and functional group of a rodlike Schiff base mesogen on blue phase stabilization in a chiral system
作者:Chiung-Cheng Huang、Yu-Chang Huang、Wei-Cheng Hsieh、Yen-Jung Chen、Shi-Kai Jiang、Bo-Hao Chen、I.-Jui Hsu、Jey-Jau Lee
DOI:10.1039/c8nj04493g
日期:——
(type I) and –NC– (type III) linkages were prepared. These mesogens possessed either difluoro substitutions at the inner-core position of the phenyl ring or hydroxy group to form intramolecular hydrogen bonding with an ester or/and imine linkage. When the appropriate concentration of chiral additive is doped into them, the incorporation of two fluoro substituents is more useful for blue phase (BP) stabilization
Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives
作者:Ashwathanarayana Gowda、Arun Roy、Sandeep Kumar
DOI:10.1016/j.molliq.2016.11.010
日期:2017.1
Herein, we reported novel banana liquid crystals derived from ethylenedioxythiophene (EDOT) central unit encompass with Schiff base. Structural charecterization of these compounds was carried out from their spectral and elemental analysis. Physical properties of all the newly synthesized compounds were investigated by polarising optical microscopy, differential scanning calorimetry, thermogravimetric
Synthesis, Structural and Mesophase Characterization of Three Ring Based Thiophene Liquid Crystals
作者:M. Kesava Reddy、K. Subramanyam Reddy、B. V. N. Phani Kumar、T. Narasimhaswamy
DOI:10.1080/15421406.2013.858013
日期:2014.4.13
Thiophene based calamitic mesogens are receiving paramount importance due to their applications in functional organic materials. The insertion of thiophene in the core unit favours a large change in mesophase characteristics as well as application properties in contrast to those mesogens with phenyl ring core alone. In this work, we report the structural as well as mesophase characterization of six mesogens which are built with a core of three phenyl rings and thiophene ring. The thiophene ring is placed at one end of the core and varied the other end with alkyl/alkoxy chains to investigate the mesophase characteristics. The molecular structures of representative mesogens are confirmed by means of FT-IR and Two-dimensional solution NMR techniques. An enantiotropic nematic phase is observed in all the cases as supported by HOPM and DSC techniques. The mesophase characteristics such as melting and clearing temperatures and phase stability are discussed. A dramatic increase in nematic phase stability for the synthesised mesogens is noticed in contrast to two phenyl ring based thiophene mesogens reported in literature.