Viscoelasticity of ambient-temperature nematic binary mixtures of bent-core and rodlike molecules
Viscoelasticity of ambient-temperature nematic binary mixtures of bent-core and rodlike molecules
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弯核和棒状分子的室温向列二元混合物的粘弹性
DOI：
10.1103/physreve.85.011702
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S.Dhara
中科院分区：
文献类型：
--
作者：
P.Sathyanarayana;V.S.R.Jampani;M.Skarabot;I.Musevic;K.V.Le;H.Takezoe;S.Dhara
我们报告的测量温度变化的物理参数在室温下的液晶混合物的双折射率（BC）和棒状分子（5CB）：静态介电常数和; splay和弯曲弹性常数;旋转粘度;和扩散系数和微球。随着BC浓度的增加，和迅速下降，而几乎保持不变。在变换的温度下（例如，当BC浓度增加到43 mol时，与纯5CB相比，5CB的活性增加了50，而5CB的活性降低了80。利用Stokes-Einstein关系式，分别求出了与Miesowicz粘度近似相等的平行于和垂直于指向矢的粘度。与纯5CB相比，在室温下的粘度分别增加了60和50倍，而在43 mol时增加了180倍。在较高的BC摩尔数下，所有粘度的硬化和过大的增强表明，BC分子的近晶簇的存在对粘弹性能有很大的影响，近晶簇的存在是由于分子沿着弓轴在α相中的受限自由旋转造成的。提出了一种可能的近晶型BC分子簇围绕微粒的附着模型。
We report measurements of the temperature variations of physical parameters in ambient-temperature nematic liquid crystal mixtures of bent-core (BC) and rodlike molecules (5CB): birefringence; static dielectric constantsand; splayand bendelastic constants; rotational viscosity; and diffusion coefficientsandof a microsphere. Bothanddecreases rapidly with increasing BC concentration, whereasremains almost constant. At a shifted temperature (e.g.,C),increases by50anddecreases by80compared to pure 5CB when the BC concentration is increased to43 molin the mixture. Viscosities parallel and perpendicular to the director,,, which are nearly equal to the Miesowicz viscositiesand, respectively, were obtained byandusing the Stokes-Einstein relation. Both the viscosities at room temperature increase by 60 and 50 times, respectively, whereasincreases by 180 times (at43 mol) compared to the corresponding values of pure 5CB. The stiffening ofand exorbitantly large enhancement in all the viscosities at a higher molof BC indicate that the viscoelastic properties are highly impacted by the presence of smectic clusters of BC molecules that results from the restricted free rotation of the molecules along the bow axis in the nematic phase. A possible attachment model of smectic type clusters of BC molecules surrounding the microparticle is presented.