Lee Seng Kue, Shi Lu, Tokita Masatoshi, Takezoe Hideo, Watanabe Junji
J Phys Chem B. 2007 Aug 2;111(30):8698-701. doi: 10.1021/jp0739014. Epub 2007 Jun 29.
Electric-field-induced transition was observed for the weakly birefringent chiral B2 phase, which is formed from the banana molecule based on the naphthalene bent core. This phase is considered to possess the twisted grain boundary (TGB)-like helical structure. When an electric field is applied, the TGB-like helix unwinds. The resulting large domain of the SmC(A)P(A) phase shows the high birefringence and simultaneously the antiferroelectric switching between SmC(A)P(A) and SmC(S)P(F) states. Through this field-induced transformation, two interesting features are obtained. First, the initially formed chiral domains are preserved even after the field-induced transformation to the unwound SmC(A)P(A) phase. This indicates the close correlation between the TGB-like helix and the layer chirality in such a way that the helical sense of the TGB-like helix is memorized as the layer chirality of the homochiral SmC(A)P(A) phase. Second, there is a critical temperature, above which the helicoidal structure is stable against the electric field. There is a competition between winding into a TGB-like structure and unwinding due to the electric field, and at higher temperatures, the helicoidal power is too strong to surpass the effect of the electric field.
在由基于萘弯曲核的香蕉分子形成的弱双折射手性B2相中观察到电场诱导转变。该相被认为具有类似扭曲晶界（TGB）的螺旋结构。施加电场时，类似TGB的螺旋会展开。由此产生的大尺寸SmC(A)P(A)相显示出高双折射，同时在SmC(A)P(A)和SmC(S)P(F)状态之间存在反铁电切换。通过这种场诱导转变，获得了两个有趣的特征。首先，即使在场诱导转变为展开的SmC(A)P(A)相之后，最初形成的手性畴仍得以保留。这表明类似TGB的螺旋与层手性之间存在密切关联，即类似TGB的螺旋的螺旋方向被记忆为纯手性SmC(A)P(A)相的层手性。其次，存在一个临界温度，高于该温度时螺旋结构对电场稳定。在形成类似TGB的结构的缠绕与电场导致的展开之间存在竞争，并且在较高温度下，螺旋力太强而无法超过电场的作用。
