Elastic properties of bimesogenic liquid crystals
Elastic properties of bimesogenic liquid crystals
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DOI：
10.1080/02678292.2013.765973
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发表时间：
2013-05-01
期刊：
影响因子：
2.2
通讯作者：
Mehl, G. H.
中科院分区：
文献类型：
--
作者：
Balachandran, R.;Panov, V. P.;Mehl, G. H.
在具有奇异柔性间隔基的双介晶液晶中发现的第二相，由于其具有许多特殊的性质，引起了人们的极大兴趣。然而，这种分子表现出向调制相转变的原因仍然不清楚。Dozov [Europhys Lett. 2001;56：247]预测负K-33可以导致其中指向矢具有展曲-弯曲或扭曲-弯曲分布的调制相位。虽然各种理论研究表明这种情况可能是有效的，但迄今为止还没有实验证据。为了研究弹性常数的影响，我们测量了二聚体材料CBC 11 CB的普通向列相在低于Nx-Nu转变0.6摄氏度的温度下的张开和弯曲弹性常数。我们的研究结果表明，弯曲常数减少了一个因素的2相比，更接近I-Nu转变，但是积极的，似乎没有趋势，K-33将外推到零或低于它的温度范围内调查。与K-11相比，K-33降低了3倍，接近Nu-Nx转变温度。
The second nematic phase found in some bimesogenic liquid crystals with an odd flexible spacer has aroused considerable interest due to many unusual properties exhibited by them. However, the reason for such molecules to exhibit transitions to the modulated phase is still unclear. Dozov [Europhys Lett. 2001;56:247] predicted that negative K-33 can lead to a modulated phase where the director has either splay-bend or twist-bend distribution. Though various theoretical studies have suggested that this scenario may be valid, no experimental evidence has so far been given. In order to study the influence of the elastic constants, we measured the splay and bend elastic constants in the ordinary nematic phase of a dimer material, CBC11CB, for temperatures down to 0.6 degrees C above the Nx-Nu transition. Our results show that the bend constant is reduced by a factor of 2 compared with that closer to the I-Nu transition but is positive and the trend does not seem that K-33 will extrapolate to zero or fall below it for the temperature range investigated. Compared to K-11, K-33 is reduced by a factor of 3, close to the Nu-Nx transition temperature.