Optically active, three-ring calamitic liquid crystals: the occurrence of frustrated, helical and polar fluid mesophases
作者:B. N. Veerabhadraswamy、D. S. Shankar Rao、S. Krishna Prasad、C. V. Yelamaggad
DOI:10.1039/c4nj02011a
日期:——
mesophases such as the blue phase-I/II (BPI or BPII) and chiral nematic (N*) and chiralsmecticC (SmC*) phases has been evidenced unequivocally with the help of polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electrical switching. Besides, the occurrence of an unknown, metastable smectic (SmX) phase below the SmC* phase has been noted. This study shows that the length of
Stable Ferroelectric Liquid Crystals Derived from Salicylaldimine-Core
作者:Bhyranalyar N. Veerabhadraswamy、D. S. Shankar Rao、Channabasaveshwar V. Yelamaggad
DOI:10.1021/acs.jpcb.5b00209
日期:2015.3.26
potential for applications in ferroelectric liquidcrystal devices. Thus, they have been substituted with a chiral tail at one end and by n-alkoxy chains of varying length at the other terminal. A detailed study confirms an indistinguishable behavior of all ten mesogens exhibiting an enantiotropic chiral smectic C (SmC*) phase besides blue phase (BP) and chiral nematic (N*) phase. The SmC* phase occurring
通过使(R)-或(S)-4-(辛烷-2-基氧基)苯胺与4-甲酰基-3-羟基苯基4-(正烷氧基)苯甲酸酯缩合,制备了五对源自水杨醛亚胺核心的对映异构体。它们被设计用来探查分子结构和同构同构之间的相关性,特别是提供具有在铁电液晶器件中应用潜力的稳定的介晶。因此,它们的一端被一个手性尾取代,n被一个-在另一个末端的长度可变的-烷氧基链。一项详细的研究证实,除了蓝相(BP)和手性向列相(N *)相以外,所有表现出对映性手性近晶C(SmC *)相的所有十种介晶均无法区分。在50-70°C的热宽度范围内发生的SmC *相显示出铁电切换,其自发极化(P s)值超过100 nC / cm 2。中间相的圆二色光谱研究证实了分子在宏观手性(螺旋)环境中的发色团。
The effect of position of (S)-2-octyloxy tail on the formation of frustrated blue phase and antiferroelectric phase in Schiff base liquid crystals
Chiral salicylaldimine-based liquid crystals in which the (S)-2-octyloxyl tail close to or far from the salicylaldimine core possesses a frustrated blue phase and an antiferroelectric SmC*A phase.
Bistable mesomorphism and supramolecular stereomutation in chiral liquid crystal azopolymers
作者:Jesús del Barrio、Rosa M. Tejedor、Luiz S. Chinelatto、Carlos Sánchez、Milagros Piñol、Luis Oriol
DOI:10.1039/b901384a
日期:——
A series of side-chain liquid crystal polymers based on an azobenzene mesogenic unit bearing a terminal chiral chain has been synthesized. The thermal and mesomorphic properties of the homo- and copolymers have been investigated by polarizing optical microscopy, DSC and X-ray diffraction. Polymers having a chiral methylheptyloxy terminal chain (P8S and P8R) exhibit surprising mesomorphic behavior, which depends on the thermal history of the sample. The influence of the molecular chirality and thermal history on the supramolecular organization of the chromophores have also been studied. Supramolecular chiral aggregation of the azobenzenes seems to be responsible for the observed chiroptical properties of these materials, both in solution and solid state (polymeric films), with the handedness controlled by the molecular chirality. Stereomutation of the chiral supramolecular organization is detected when polymeric films of P8S and P8R experience a different thermal history.
我们合成了一系列基于带有末端手性链的偶氮苯介原单元的侧链液晶聚合物。通过偏振光学显微镜、DSC 和 X 射线衍射研究了均聚物和共聚物的热性质和介形性质。具有手性甲基庚氧基末端链(P8S 和 P8R)的聚合物表现出令人惊讶的介形态行为,这种行为取决于样品的热历史。此外,还研究了分子手性和热历史对发色团超分子结构的影响。偶氮苯的超分子手性聚集似乎是这些材料在溶液和固态(聚合物薄膜)中观察到的手性特性的原因,其手性由分子手性控制。当 P8S 和 P8R 的聚合物薄膜经历不同的热历史时,可以检测到手性超分子结构的立体变异。
Broad temperature range of cubic blue phase present in simple binary mixture systems containing rodlike Schiff base mesogens with tolane moiety
Four simple rodlike Schiff base mesogens with tolane moiety were synthesized and applied to stabilize cubic blue phases (BPs) in simple binary mixture systems for the first time. When the chiral additive ISO(6OBA)2 or R811 was added into a chiral salicylaldimine-based compound, the temperature range of the cubic BP could be extended by more than 20 °C. However, when the chiral Schiff base mesogen was blended with chiral dopant possessing opposite handedness, S811, BPs could not be observed. Interestingly, the widest temperature range of the cubic BPs (∼35 °C) could be induced by adding the rodlike chiral dopant R811 or S811 into the rodlike racemic Schiff base mesogen with hydroxyl group. On the basis of our experimental results and molecular modeling, the appearance and temperature range of the BPs are affected by the dipole moment and the biaxiality of the molecular geometry. Accordingly, we demonstrated that the hydroxyl group and the methyl branch in this type of Schiff base mesogen play an important role in the stabilization of BPs.