Rotational viscosity measurements of bent-core nematogens
Rotational viscosity measurements of bent-core nematogens
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弯芯线虫的旋转粘度测量
DOI：
10.1039/c3sm00008g
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发表时间：
2013
期刊：
影响因子：
3.4
通讯作者：
C. Tschierske
中科院分区：
文献类型：
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作者：
A. Chakraborty;M. K. Das;B. Das;A. Lehmann;C. Tschierske
用两种简单而精确的探针方法研究了结构、性质和分子缔合对3种不同端链长度的4-氰基间苯二酚双核衍生物（1/7，1/9和1/10）的指向矢响应时间（τ0）和旋转粘度（γ1）的影响。两种方法所得结果吻合较好，偏差约为10- 15%。γ1值比传统的棒状向列相高一个数量级以上。测量了这些化合物的双折射、介电各向异性、展曲和弯曲弹性常数以及弛豫时间。对于较低的同系物（1/7，1/9），在介电各向异性（Δe）中观察到反转，而较高的同系物（1/10）在整个介晶范围内表现出负的Δe。展曲弹性常数（K11）被发现是比较大于弯曲弹性常数（K33），然而，在接近低温CybC相（相包括拉长cybotactic集群）K33表现出一个小的pretransitional发散。对于所有三种化合物，发现在接近CybC相时，旋转粘度系数（γ1）的大小表现出强烈的增强，而在CybC相中，发现活化能比正常的kalamitics高近一个数量级。观察到的行为被解释考虑到强偶极相关的双核心分子和存在的短程cybotactic集群，它们的逐渐增长和均匀排列下存在的强表面锚定。
Two simple but precise probing methods have been utilized to investigate the influence of structure, properties and molecular association on the director response time (τ0) and hence on the rotational viscosity (γ1) in the nematic phase of three 4-cyanoresorcinol bent-core derivatives (1/7, 1/9 and 1/10) having different terminal chain lengths. The results obtained from the two methods are in good agreement with a small deviation of about 10–15%. The γ1 values are more than an order of magnitude higher compared to the conventional calamitic nematics. Measurements of birefringence, dielectric anisotropy, splay and bend elastic constants and relaxation time of these compounds have also been carried out. For the lower homologues (1/7, 1/9) an inversion in dielectric anisotropy (Δe) is observed in the nematic phase, while the higher homologue (1/10) exhibits negative Δe throughout the entire mesomorphic range. The splay elastic constant (K11) is found to be comparatively greater than the bend elastic constant (K33); however, on approaching the low temperature CybC phase (a phase comprising elongated cybotactic clusters) K33 exhibits a small pretransitional divergence. For all three compounds the magnitude of the rotational viscosity coefficient (γ1) is found to exhibit a strong enhancement on approaching the CybC phase, while in the nematic phase activation energies are found to be nearly an order of magnitude higher than the normal calamitics. The observed behaviours are explained by considering the strong dipolar correlation of the bent-core molecules and the existence of the short range cybotactic clusters, their gradual growth and uniform alignment under the presence of strong surface anchoring.
弯曲核向列液晶的张开弯曲弹性
DOI：
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发表时间：
2010
期刊：
Phys.Rev.E
影响因子：
--
作者：
P.Sathyanarayana;M.Mathew;Q.Li;V.S.S.Sastry;B.Kundu;K.V.Le;H.Takezoe;S.Dhara
通讯作者：
S.Dhara
非手性弯核分子向列相中电对流形成的交替扭曲结构
DOI：
--
发表时间：
2008
期刊：
Phys. Rev. E 77
影响因子：
--
作者：
S. Tanaka;S. Dhara;B. K. Sadashiva;Y. Shimbo;Y. Takanishi;F. Araoka;K. Ishikawa;H. Takezoe
通讯作者：
H. Takezoe