Orientational order in liquid crystals exhibited by some binary mixtures of rod-like and bent-core molecules
Orientational order in liquid crystals exhibited by some binary mixtures of rod-like and bent-core molecules
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棒状分子和弯核分子的一些二元混合物表现出液晶中的取向顺序
DOI：
10.1140/epje/i2010-10556-8
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
N. V. Madhusudana
中科院分区：
文献类型：
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作者：
B. Kundu;R. Pratibha;N. V. Madhusudana
我们报告了由棒状 (R) 分子制成的 4-n-辛氧基 4'-氰基联苯以及该化合物与由弯芯 (BC) 制成的 1,3-亚苯基双[4-(3-甲基苯甲酰氧基)] 4' -n-十二烷基联苯 4'-羧酸酯的五种混合物中向列 (N) 和部分双层 SmA (SmAd) 相中光学双折射的温度变化的测量结果分子。双折射随着 BC 分子浓度 x 的增加而降低，但宏观有序参数最初降低到 BC 分子的 11mol%，随后随着 x 的增加而增加。这是由于 BC 分子可能形成极性簇。 BC 分子的取向在 N 相和 SmAd 相之间变化，并且两相中的双折射数据意味着 BC 分子的扭结角为 ∼ 90°，而不是通过最小化分子能量的计算获得的 ∼ 110°。对含有 11mol% BC 分子的混合物进行红外光谱测量已用于估计 R 分子的分子有序参数 S，并为 BC 分子相对较小的扭结角提供额外的支持。
We report measurements of the temperature variations of the optical birefringence in the nematic (N) and partial bilayer SmA (SmAd) phases in 4-n-octyloxy 4′ -cyanobiphenyl made of rod-like (R) molecules and five mixtures of this compound with 1,3-phenylene bis[4-(3-methylbenzoyloxy)] 4′ -n- dodecylbiphenyl 4′ -carboxylate, made of bent-core (BC) molecules. The birefringence decreases with the concentration x of the BC molecules but the macroscopic order parameter initially decreases upto 11mol% of BC molecules and subsequently increases with x . This is attributed to the possible formation of polar clusters of BC molecules. Orientation of BC molecules changes between the N and SmAd phases and the birefringence data in the two phases imply that the kink angle of the BC molecules is ∼ 90° rather than ∼ 110° as obtained from calculations which minimize the energy of the molecule. IR spectroscopic measurements on the mixture with 11mol% of BC molecules have been used to estimate the molecular order parameter S of the R molecules, and to provide additional support for a relatively small kink angle of BC molecules.