Controlling spontaneous mirror symmetry breaking in cubic liquid crystalline phases by the cycloaliphatic ring size

Abstract

Achiral compounds with an alicyclic apex form a chiral cubic phase either for a specific ring-size or by mixing of small- and large-ring compounds.

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

“…They can deviate from these values, for example, if the alkyl chain at the apex is especially long (X = OC 10 H 21 ), or as the length and shape of the core is changed, though the fundamental phase sequence remains the same. [117] Depending on the contribution of the substituent to the volume effect and the twist, the lattice parameter can increase, as observed for the BABHs and ANBCs, [101,103,104,107,108] remain almost constant, as reported here for compounds 3/ m X n and 3a/Y, or even decreases with increasing volume of the substituents, as recently reported for benzil-based polycatenars. [154] However, in all cases, the twist angle increases with the apex volume, leading to the sequence Ia3 d (L) -I23-Ia3 d (S) .…”

“…Thus, tailoring of the cubic phase structure and mirror symmetry breaking is not only achievable by the design of individual compounds, but also by mixing compounds with different sizes of the substituents. [111,117]…”

“…Whereas no effect of replacement of benzene at the apex by thiophene is observed, replacing benzene by cyclohexane changes the cubic phase type from Ia3 d to I23, indicating that the aliphatic ring acts as a larger substituent, especially [87], for compounds 3a/Cy, 3a/Ad and 3a/CEt 3 , see ref. [117], for all other data, see Tables S1 and S2 in the Supporting Information).…”

“…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.…”

Spontaneous mirror symmetry breaking in benzil-based soft crystalline, cubic liquid crystalline and isotropic liquid phases

“…The I 23 [ * ] phase obviously allows for these twist angles a better fit of the helical pitch length with junction distances and inter-junction twist angles than in the competing Ia 3[combining macron] d lattices. 12a , 25 This phase sequence was also reported for the Cub bi phases of other rod-like molecules 18a , 19 , 29 and it is observed in the contact regions between the achiral Ia 3[combining macron] d (L) and Ia 3[combining macron] d (S) phases of 3/2 and 3/12–3/16 , respectively, where a concentration gradient develops, and in a certain concentration range the chiral conglomerate of the I 23 [ * ] phase is induced ( Fig. 2i–k ).…”