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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]

Cyanobiphenyl (CB) mesogenic molecules are a focal point in liquid crystal (LC) research and applications due to their chemical stability, ease of synthesis, broad mesophase temperature range, and other advantageous properties. The introduction of chirality into LC systems offers unique optical and mechanical properties with great potential, and exploring the CB building block in chiral LC dimers presents a promising avenue for further research. In this study, we present the synthesis of chiral and racemic dimers bearing a chiral center as part of their flexible spacer and two CB moieties at the ends, i.e. the first chiral CB dimers. The investigation includes ester and amide linking groups near the chiral center to evaluate the impact of molecular flexibility on mesomorphic behavior and helical twisting power (HTP). The synthesis of racemic and enantiomerically pure dimers enabled the comparison of their mesogenic properties. Our results revealed CB dimers bearing ester linking group exhibit rich nematic polymorphism, including the rarely obtained room-temperature twist-bend nematic (NTB) phase. In contrast, the amide linking group suppresses LC properties but significantly enhances the HTP. These findings highlight the importance of intermolecular interactions and the balance of flexibility and rigidity near the chiral center in achieving desirable mesomorphic properties. [ABSTRACT FROM AUTHOR]

Spontaneous symmetry breaking and emergent polar order are each of fundamental importance to a range of scientific disciplines, as well as generating rich phase behaviour in liquid crystals (LCs). Here, we show the union of these phenomena to lead to two previously undiscovered polar liquid states of matter. Both phases have a lamellar structure with an inherent polar ordering of their constituent molecules. The first of these phases is characterised by polar order and a local tilted structure; the tilt direction processes about a helix orthogonal to the layer normal, the period of which is such that we observe selective reflection of light. The second new phase type is anti-ferroelectric, with the constituent molecules aligning orthogonally to the layer normal. This has led us to term the phases the Sm C P H and SmAAF phases, respectively. Further to this, we obtain room temperature ferroelectric nematic (NF) and Sm C P H phases via binary mixture formulation of the novel materials described here with a standard NF compound (DIO), with the resultant materials having melting points (and/or glass transitions) which are significantly below ambient temperature. The new soft matter phase types discovered herein can be considered as electrical analogues of topological structures of magnetic spins in hard matter. Spontaneous symmetry breaking and emergent polar order are key to liquid crystal phase behaviour. This study reveals two new polar liquid states with lamellar structures, providing novel insights into electrical analogues of magnetic spin structures. [ABSTRACT FROM AUTHOR]

The discovery of fluid states of matter with spontaneous bulk polar order is appreciated as a major discovery in the fields of soft matter and liquid crystals. Typically, this manifests as polar order superimposed atop conventional phase structures and is thus far limited to orthogonal phase types. Here we report a family of materials which exhibit a previously unseen state of matter which we conclude is a polar smectic C phase, and so we term it SmCP. 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., (© 2024 Wiley‐VCH GmbH.)