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Distinct Columnar and Lamellar Liquid Crystalline Phases Formed by New Bolaamphiphiles with Linear and Branched Lateral Hydrocarbon Chains
Author(s) -
Prehm Marko,
Enders Claudia,
Anzahaee Maryam Yahyaee,
Glettner Benjamin,
Baumeister Ute,
Tschierske Carsten
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800141
Subject(s) - mesophase , lamellar structure , crystallography , alkyl , liquid crystal , phase (matter) , thermotropic crystal , columnar phase , chemistry , materials science , stereochemistry , organic chemistry , liquid crystalline , optoelectronics
A universal building block for the convergent synthesis of a wide variety of different T‐shaped ternary amphiphiles was developed and used for the synthesis of a series of new liquid‐crystalline materials composed of a rigid biphenyl core with polar glycerol groups at both ends and linear or branched alkyl chains in a lateral position. In addition, compounds with bulky achiral (2,4,6‐trimethylphenoxy, adamantane‐1‐carboxylate, benzoate) or chiral (menthyl or cholesteryl) substituents attached to the end of the lateral alkyl chain were also investigated. In all cases the lateral chains were connected to the aromatic core by an ether linkage. The effect of the ether linking unit on mesophase stability and mesophase type is discussed with respect to conformational effects. The liquid‐crystalline phases were investigated by polarizing microscopy, calorimetry, and X‐ray diffraction of surface aligned samples. Upon enlarging the lateral chains a series of different polygonal cylinder phases was observed, which were replaced by lamellar phases and a non‐cylinder hexagonal columnar phase by further increasing the size of these substituents. Remarkably, only pentagonal, hexagonal, and giant hexagonal cylinder phases could be observed, whereas mesophases composed of cylinders with a smaller number of sides are missing. No distinct chirality effects were observed for the menthyl‐ and cholesteryl‐substituted compounds. However, the rodlike shape of the polycyclic cholesteryl core leads to a unique phase structure combining an organization of the alicyclic cholesteryl cores perpendicular to the layer planes and the aromatic biphenyl cores parallel to the layer planes.