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The spontaneous polarisation of the SmCP phase is over two orders of magnitude larger than that found in conventional ferroelectric SmC phase of chiral materials used in some LCD devices. Fully atomistic molecular dynamics simulations faithfully and spontaneously reproduce the proposed structure and associated bulk properties; comparison of experimental and simulated X‐ray scattering patterns shows excellent agreement. The materials disclosed here have significantly smaller dipole moments than typical polar liquid crystals such as RM734 which suggests the role of molecular electrical polarity in generating polar order is perhaps overstated, a view supported by consideration of other molecular systems. [ABSTRACT FROM AUTHOR]

Polar liquid crystals possess 3D orientational order coupled with unidirectional electric polarity, yielding fluid ferroelectrics. Such polar phases are generated by rod‐like molecules with large electric dipole moments. 2,5‐Disubstituted 1,3‐dioxane is commonly employed as a polar motif in said systems, and herein it is shown to suffer from thermal instability as a consequence of equatorial‐trans to axial‐trans isomerism at elevated temperatures. Isosteric building blocks are utilized as potential replacements for the 1,3‐dioxane unit, and in doing so new examples of fluid ferroelectric systems are obtained. For binary mixtures of certain composition, the emergence of a new fluid antiferroelectric phase, a finding not observed for either of the parent molecules, is observed. This study also reveals a critical tipping point for the emergence of polar order in otherwise apolar systems. These results hint at the possibility for uncovering new highly ordered polar liquid‐crystalline phases and delineate distinct transition mechanisms in orientational and polar ordering. [ABSTRACT FROM AUTHOR]

The synthesis and characterisation of ten members of the 4[{[4({5[4((4-cyanophenyl)phenyl]oxy)pentoxy}yl)phenyl]methylidene}amino] phenyl 4-alkyloxybenzoates is presented. These dimers are referred to using the acronym CBO5OIBeOm in which m refers to the number of carbon atoms in the terminal chain and varies from 1 to 10. The CBO5OIBeOm series exhibits nematic (N), twist-bend nematic (NTB), and smectic A (SmA) phases depending on the length of the terminal chain. Although the NTB phase is observed, these dimers do not exhibit the twist-bend smectic C (SmCTB) phases. By comparison, the structurally similar CB6OIBeOm series does exhibit the SmCTB phases, and this strongly suggests that the formation of the SmCTB phase is more sensitive to molecular curvature than that of the NTB phase. [ABSTRACT FROM AUTHOR]

Cyanobiphenyl-based liquid crystal dimers containing a disulfide link in the spacer, the 4-[4-[2-[2-[4-(4-cyanophenyl)phenyl]alkyldisulfanyl]alkyl]-phenyl]benzonitriles (CBnSSnCB), are reported. The alkyl fragment is varied from two to nine carbon atoms, and all eight homologues exhibit nematic behaviour. In addition, the dimer containing heptamethylene fragments (CB7SS7CB) exhibits a twist-bend nematic phase despite having an even-membered spacer. The values of the nematic–isotropic transition temperature, TNI, are higher for dimers containing an odd number of carbon atoms in each alkyl fragment. This surprising behaviour is interpreted in terms of the C-S-S-C torsion angle being around 88° that ensures that the molecular shape is bent irrespective of the parity of the alkyl fragments. For odd-membered fragments, however, the average shape is less bent and higher values of TNI are observed. The more uniform molecular curvature of CB7SS7CB accounts for the observation of the NTB phase. We also report the behaviour of two members of the 4-[4-[3-[2-[4-(4-cyanophenyl)phenyl]alkyldisulfanyl]-alkyl]phenyl]benzonitriles (CBnSmCB) which contain a thioether link embedded in the spacer. Both dimers exhibited nematic behaviour. The thioether link reduces the value of TNI compared to that of the dimer with an alkyl spacer. A much larger decrease in the nematic-twist-bend nematic temperature is observed and is attributed to a change in shape. [ABSTRACT FROM AUTHOR]

A convenient synthetic route based on a sodium-mediated aromatic cross-coupling reaction is described for the multi-gram preparation of the ω-bromo-1-(4-cyanobiphenyl-4'−yl) alkanes (CBnBr, n = 2–10). These materials are not only key intermediates in the synthesis of oligomers and polymers but also exhibit fascinating liquid crystal behaviour in their own right. Nematic behaviour is observed for n⩾5, and the nematic-isotropic transition temperature, TNI, increases in essentially a linear manner on n. The properties of the ω-bromo-1-(4-cyanobiphenyl-4'−yloxy) alkanes (CBOnBr, n = 2–9) are also reported, and nematic behaviour is seen for n⩾3. The values of TNI show a weak odd-even effect on n in which the odd members show the higher values. The sense of this alternation is opposite to that seen for the 4-alkyloxy-4'-cyanobiphenyls, and this is attributed to the steric bulk of the bromine atom. The absence of smectic behaviour for both the CBnBr and CBOnBr series is attributed largely to electrostatic interactions that would arise from the concentration of the bromine atoms at the layer interfaces in an interdigitated smectic phase. A comparison of a range of cyanobiphenyl-based materials containing a chain with a terminal polar or polarisable group suggests that their phase behaviour is governed largely by their average molecular shapes. [ABSTRACT FROM AUTHOR]