Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8562, Japan.
J Phys Chem B. 2013 May 23;117(20):6290-3. doi: 10.1021/jp401057n. Epub 2013 May 13.
In order to clarify the origin of the X-ray diffraction peak corresponding to the smectic-like layer ordering appearing even in the nematic phase over a wide temperature range above the nematic-smectic A (NA) phase transition in liquid crystal (LC) molecules with a hydroxy group, we investigated the critical behavior of bend elastic constants and the correlation length of the smectic-like ordering in the N phase. It is found that cybotactic clusters with the transient layer ordering grow up extremely even far above the NA phase transition, and the critical exponent of the correlation length of the cybotactic clusters is estimated anomalously larger than that of conventional LC materials. Furthermore, we measured diffusion constants parallel and perpendicular to the director in the N phase, and concluded that cybotactic clusters with the smectic layer ordering create a finite potential barrier to prevent diffusion of the molecules parallel to the director as well as the true smectic A layer structure.
为了阐明在宽温域范围内，即使在向列-近晶 A（NA）相转变之上的向列相区中也出现类似近晶层序的 X 射线衍射峰的起源，我们研究了具有羟基的液晶（LC）分子的弯曲弹性常数的临界行为和近晶相区中类似近晶层序的相关长度。发现具有瞬变层序的胶束簇在远高于 NA 相转变的温度下也会急剧增长，并且胶束簇的相关长度的临界指数异常大于常规 LC 材料的临界指数。此外，我们还测量了在 N 相区中平行和垂直于指向矢的扩散常数，并得出结论：具有近晶层序的胶束簇会形成有限势垒，以阻止分子沿指向矢的扩散以及真正的近晶 A 层结构。
