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Lamellar Liquid Crystals of In‐Plane Lying Rod‐Like Mesogens with Designer Side‐Chains: The Case of Sliding versus Locked Layers
Author(s) -
Prehm Marko,
Enders Claudia,
Mang Xiaobin,
Zeng Xiangbing,
Liu Feng,
Ungar Goran,
Baumeister Ute,
Tschierske Carsten
Publication year - 2018
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.201802050
Subject(s) - lamellar structure , materials science , liquid crystal , branching (polymer chemistry) , side chain , alkyl , chemical physics , soft matter , crystallography , supramolecular chemistry , isotropy , rod , polymer , nanotechnology , chemistry , composite material , crystal structure , optics , physics , optoelectronics , organic chemistry , colloid , medicine , alternative medicine , pathology
The dimensionality of self‐assembled nanostructures plays an essential role for their properties and applications. Herein, an understanding of the transition from weakly to strongly coupled layers in soft matter systems is provided involving in‐plane organized π‐conjugated rods. For this purpose, bolaamphiphilic triblock molecules consisting of a rigid biphenyl core, polar glycerol groups at the ends, and a branched (swallow‐tail) or linear alkyl or semiperfluoroalkyl chain in lateral position have been synthesized and investigated. Besides weakly coupled lamellar isotropic (Lam Iso ), lamellar nematic (Lam N ) and sliding lamellar smectic phases (Lam Sm ), a sequence of three distinct types of strongly coupled (correlated) lamellar smectic phases with either centered ( c 2 mm ) or non‐centered rectangular ( p 2 mm ) lattice and an intermediate oblique lattices ( p 2) were observed depending on chain length, chain branching and degree of chain fluorination. This new sequence is explained by the strengthening of the layer coupling and the competition between energetic packing constraints and the entropic contribution of either longitudinal or tangential fluctuations. This example of directed side chain engineering of small generic model compounds provides general clues for morphological design of two‐dimensional and three‐dimensionally coupled lamellar systems involving larger π‐conjugated molecular rods and molecular or supramolecular polymers, being of actual interest in organic electronics and nanotechnology.