A Nanohelicoidal Nematic Liquid Crystal Formed by a Non‐Linear Duplexed Hexamer

Abstract

The twist‐bend modulated nematic liquid‐crystal phase exhibits formation of a nanometre‐scale helical pitch in a fluid and spontaneous breaking of mirror symmetry, leading to a quasi‐fluid state composed of chiral domains despite being composed of achiral materials. This phase was only observed for materials with two or more mesogenic units, the manner of attachment between which is always linear. Non‐linear oligomers with a H‐shaped hexamesogen are now found to exhibit both nematic and twist‐bend modulated nematic phases. This shatters the assumption that a linear sequence of mesogenic units is a prerequisite for this phase, and points to this state of matter being exhibited by a wider range of self‐assembling structures than was previously envisaged. These results support the double helix model of the TB phase as opposed to the simple heliconical model. This new class of materials could act as low‐molecular‐weight surrogates for cross‐linked liquid‐crystalline elastomers.

A novel nematic-like mesophase induced in dimers, trimers and tetramers doped with a high helical twisting power additive

“…We next prepared mixtures using trimeric and tetrameric host materials that exhibit the TB phase in their neat state: A6 3 ; T 3 9; 42 T 4 9; 42,43 O4 7 . 44 Other materials possibly of interest, namely A6 4 , 48 O6 7 , 44 and D11 3 (2) 29 are not presently available to us in sufficient quantity for the accurate creation of mixtures.…”

“…23,24 In addition to being found in achiral materials, a number of chiral dimers/bimesogens are known to exhibit the TB phase. 6,7,25 In addition to low molecular weight dimers the TB phase is also found in oligomers, [26][27][28][29] polymers 30,31 and possibly lyotropic systems. 32 Several examples of transitions from the TB phase into smectic phases are known, such as smectic [33][34][35][36][37] and B 6 phases.…”

Molecular Flexibility and Bend in Semi‐Rigid Liquid Crystals: Implications for the Heliconical Nematic Ground State

“…[1][2][3] Different LC mesophase are principally characterised by their degree of orientational and/orp ositional order;f or example, the nematic LC phase possesses long range orientational order with short range positional order,w hereasl amellar phases also exhibit positional order in one dimension. [10][11][12] Although this phase is principally exhibited by liquid-crystalline dimers, in which two rigid sections are adjoined by a( semi-) flexible spacer, [13,14] it has also been observed in semi-rigid bent-core materials, [15] liquid crystalline nmers [16][17][18][19] and polymers. [4][5][6][7][8][9] The N TB phase is therefore chiral despite being typicallyf ormed by achiralm olecules, although ah andfulo fc hiral materials are also known to exhibit this phase.…”

A Novel Nematic-Like Mesophase Induced in Dimers, Trimers and Tetramers Doped with a Highly Chiral Additive

“…Experimental results suggest it is primarily molecular shape [18][19][20] and the gross bend-angle that appear to dictate the incidence of this phase, [20][21][22] supporting the findings of earlier theoretical treatments. 23,24 In addition to low molecular weight dimers the TB phase is also found in oligomers, [25][26][27][28] polymers 29,30 and possibly lyotropic systems. 31 Several examples of transitions from the TB phase into smectic phases are known, such as smectic [32][33][34][35][36] and B 6 phases.…”