Supramolecular liquid crystals exhibiting a chiral twist-bend nematic phase

Abstract

<p>The characterisation of a selection of novel, chiral supramolecular liquid crystals formed by hydrogen-bonding is reported; these are the first examples of the chiral twist-bend nematic phase (N*TB) induced by H-bonding through molecular recognition.</p>

Twist-bend nematics and heliconical cholesterics: a physico-chemical analysis of phase transitions and related specific properties

“…The Cano-Grandjean texture of N * phase is observed in a wide temperature range of 52.2 -23.3 °C (Figure6(g), (h)), and the short helix pitch of the N * phase allows us to observe the Bragg reflection. In a similar way as noted earlier[8,19], at about 23.3 °C the oily-streak texture of N * phase undergoes transition to N * tb (Figure 6 (h)) with appearance of a polygonal texture with chain-like defects (Figure 6 (i)). On further cooling, at about 20.8 °C the blocky N * tb texture of the heliconical mixture (Figure 6 (j)) is observed.…”

“…Recently, however, it was shown that some banana-shaped molecules consisting of two identical or near-identical mesogenic units connected by an oddnumbered alkyl or alkoxy chain can form, at temperatures below their nematic range, another distinct liquid crystalline phasea phase with no smectic-like translational ordering, but with a rather peculiar kind of molecular arrangement with periodic twist and bend deformation of the director distribution. Such phase seems to be first reported in [5], and was later generally recognized as the "twist-bend nematic phase" ( [6][7][8][9][10] and references therein) and designated as Ntb. In the Ntb phase, the director forms a conical helix, and chirality appears spontaneously with equal fractions of helically-ordered "domains" of opposite handedness from an achiral liquid crystal at the molecular level.…”

All-atom simulations of bent liquid crystal dimers: the twist-bend nematic phase and insights into conformational chirality

“…[4][5][6][7] The requisite bent molecular shape is exhibited in dimers with a hydrocarbon spacer of odd parity. Other dimeric mesogens, [8][9][10][11][12][13][14][15][16][17] bent-core species, 18,19 and supramolecular hydrogen-bonded systems [20][21][22][23] have been reported to manifest the N TB phase. Despite the significant number of materials investigated, a general structure-property relationship for the N TB phase remains elusive; although, it is found that a spatially uniform curvature of the molecule is necessary to form the N TB phase regardless of the underlying chemical groups.…”

New patterns of twist-bend liquid crystal phase behaviour: the synthesis and characterisation of the 1-(4-cyanobiphenyl-4′-yl)-10-(4-alkylaniline-benzylidene-4′-oxy)decanes (CB10O·m)

“…These consist of molecules containing two mesogenic groups connected by a spacer having an odd number of atoms (see, for example, ref. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] although other structures such as higher oligomers, [30][31][32][33][34][35][36] semi-rigid bent core liquid crystals, 37,38 and hydrogen-bonded systems [39][40][41][42][43] are also known to support the formation of the N TB phase. The search for the twist-bend smectic phases has also been focussed on bent mesogenic dimers, but in order to drive smectic phase formation, the molecular design must also incorporate molecular inhomogeneity.…”