The influence of lateral fluorination and cyanation on the mesomorphism of polycatenar mesogens and the nature of the SmC phase therein

Abstract

Several series of tetracatenar mesogens having different lateral substituents (–F, –CN, –CF3) on the central ring have been synthesised and their mesomorphism investigated by polarising microscopy, DSC and small-angle X-ray scattering methods.

Helical Networks of π‐Conjugated Rods – A Robust Design Concept for Bicontinuous Cubic Liquid Crystalline Phases with Achiral Ia3¯d and Chiral I23 Lattice

“…Though the 3/1 tetracatenars (Figure 9d) form predominately Cub bi phases too, the symmetric 2/2 tetracatenars (Figure 9e) are much more sensitive to structural modifications and have, if any, only small Cub bi ranges beside the dominant lamellar and columnar phases. [69,116,[120][121][122][123][124] One may argue that, on average, rafts of antiparallel 3/1 tetracatenars are equivalent to those of 2/2 Figure 8. Summary of the relations between molecular structure, helical twist, cubic phase type, and cubic phase stability of compounds 3/ m X n and 3a/Y; the slight overlap of the helical twist angles results from uncertainties in the determination of the molecular volumes by the used increments [130] and possible effects of electrostatic core-core interactions, additionally contributing to the self-assembly.…”

“…The most prominent are rod-like hydrogen bonded dimers of 4′-n-alkoxy-3′-nitrobiphenyl-4-carboxylic acids (ANBCs), [100][101][102][103][104] the dibenzoylydrazines (BABHs) [105][106][107][108][109][110][111] (Figure 1c,d), [16,17,108,110] and tetracatenar molecules, which can have either a symmetric or a nonsymmetric distribution of the alkyl chains (Figure 1e,f). [112][113][114][115][116][117][118][119][120][121][122][123][124] Nevertheless, even these compounds are very sensitive to minor molecular structural variations. For example, only the NO 2 -and CN-substituted biphenyl carboxylic acids ( Figure 1d) form Cub bi phases, whereas the nonsubstituted or related halogenated compounds do not.…”

“…[125] Likewise, symmetric tetracatenars with any substituent (e.g., CH 3 , F, CN) replacing only one H-atom at the core unit do not form any Cub bi phase. [116] Therefore, it is presently not possible to efficiently tailor the phase type and application relevant properties (e.g., band gap) of these compounds by molecular design.…”

Ionic N-phenylpyridinium tetracatenar mesogens: competing driving forces in mesophase formation and unprecedented difference in phase stabilisation within a homologous series

“…S10) where the central ring bears a lateral F, CN, CF 3 or C 15 H 31 group. 21 Interestingly, however, Figures S11 and S12 show phase diagrams for tetracatenar silver triflate and dodecylsulfate complexes, respectively, and here there is an increase in mesophase stability from the cubic to the columnar phase (there is no SmC phase in these materials). Other examples of this behaviour are found for related tetra-and hexa-catenar complexes, and thus mesophase stabilisation with increasing chain length would seem to be an effect of an anion and not simply a lateral group (Fig.…”

Mesomorphism and Photophysics of Some Metallomesogens Based on Hexasubstituted 2,2′:6′, 2′′‐Terpyridines

“…In the present case the phase is of a lower symmetry, and can be visualised as a lamellar phase with antiperistaltic undulations . We may argue that on increasing the temperature, the volume of the chains increases substantially and, since they are connected to the aromatic core, the divergence from a flat‐layer structure and the induction of undulations appears to be the best compromise found in order to remain self‐organised before eventually melting to the isotropic liquid.…”