Oligomeric odd-even effect in liquid crystals

被引:36
作者
Saha, Rony [1 ]
Babakhanova, Greta [2 ,3 ]
Parsouzi, Zeinab [1 ]
Rajabi, Mojtaba [1 ]
Gyawali, Prabesh [1 ]
Welch, Chris [4 ]
Mehl, Georg H. [4 ]
Gleeson, James [1 ]
Lavrentovich, Oleg D. [1 ,2 ,3 ]
Sprunt, Samuel [1 ]
Jakli, Antal [1 ,2 ,3 ]
机构
[1] Kent State Univ, Phys Dept, Kent, OH 44242 USA
[2] Kent State Univ, Adv Mat & Liquid Crystal Inst, Kent, OH 44242 USA
[3] Kent State Univ, Chem Phys Interdisciplinary Program, Kent, OH 44242 USA
[4] Univ Hull, Dept Chem, Kingston Upon Hull, N Humberside, England
基金
英国工程与自然科学研究理事会; 美国国家科学基金会;
关键词
NEMATOGENIC MOLECULES; NEMATIC PHASE; DIMERS; CORE; PROGRESSION; ELASTICITY; TRIMERS; ORDER; NANO;
D O I
10.1039/c9mh00428a
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Odd-even effects, oscillations in properties of materials comprised of an odd or even number of connected repeating units, are well-known phenomena in materials science. In organic materials, they are usually associated with the number of methylene groups in aliphatic chains. In this work, we unveil multiple signatures of a new odd-even effect in liquid crystals that occurs at the larger scale of molecular moieties that by themselves express liquid crystalline behavior. We demonstrate that oligomeric liquid crystals, with n = 1-4 number of rigid mesogenic segments connected by flexible aliphatic chains with an odd number of methylene groups, produce an odd-even effect in optical anisotropy and the bend elastic constant of the liquid crystal oligomer. This effect is different from the usual odd-even effects with respect to the parity of carbon atoms in an aliphatic chain and can be understood in term of the average molecular shape and the associations between n-mers based on the packing of these shapes. We also show that, in spite of the fact that there is no long-range electron density modulation, careful analysis of synchrotron SAXS results can provide important information about the molecular associations in the N and N-TB phases that other techniques cannot access. This novel odd-even effect opens up a new mode to optimize phase and optical behavior.
引用
收藏
页码:1905 / 1912
页数:8
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