arXiv subjects

Vladimíra Novotná

Publications and source records attributed to Vladimíra Novotná.

5 recordsLinked to original sources

arXiv2026

The effect of side chain length on the mesomorphic properties of ferroelectric nematogens

The discovery of ferroelectric nematic phase opened new directions in the field of soft matter chemistry and physics. In this paper, we have modified a previously reported ferroelectric nematogen based on molecular structure with dimethylamino-terminated part. We have prepared two new homologues by prolonging a side chain and investigated the effect of its length on the mesomorphic properties. While previously reported homologues exhibited a direct phase transition from the isotropic (Iso) to the ferroelectric nematic phase (NF), for prolonged alkyl chain there is a narrow nematic phase (N) in between. For new compounds, we have established their mesomorphic and material properties. We have confirmed ferroelectricity of the NF phase by the polarization, SHG signal and permittivity. Finally, we have compared these parameters with respect to the side-chain length and discussed new effects, discovered for prolonged homologues due to the presence of an additional N phase.

cond-mat.soft↗

arXiv2026

The effect of fluorine or chlorine substitution on mesomorphic properties of ferroelectric nematic liquid crystals

Ferroelectric nematic phase (NF) represents an attractive and foremost field of liquid crystals, combining fluidity with ferroelectricity. NF materials exhibit large polarization values and remarkable non-linear optical properties. We have designed an original molecular structure with halogen substituents in the position of an electron donating group. In a prolonged molecular core, such a modification led to the presence of the ferroelectric nematic phase (NF) below the nematic one. Besides, an application of Cl atom in the molecular core of one of the presented materials has been utilized for the first time for ferroelectric nematogens. We have examined mesogenic behaviour and ferroelectric characteristics of the NF phase. In the NF phase for the cell with antiparallel rubbing, we have detected a textural transformation, which evidences strong polar character of anchoring at the surfaces. The presented results provide valuable insight into the design of ferroelectric nematic liquid crystalline compounds.

cond-mat.soft↗

arXiv2024

Tilt or twist-competing synclinic and anticlinic interactions in SmC phases of bent-core mesogens

Recent liquid-crystalline (LC) research is focused on structurally new molecular systems distinct from simple nematic or smectic phases. Sophisticated molecular shape may reveal structural complexity, combining helicity and polarity. Achiral symmetry-breaking in bent-core molecules leads to propensity for synclinic and anticlinic molecular structures within consecutive smectic layers. Moreover, despite their achiral character, dimers readily adopt helical phases. In our study, we investigated a hybrid molecular structure incorporating both characteristics, namely a rigid-bent core and an attached bulky polar group via a flexible spacer. To perform phase identification, we enriched the standard experimental methods with the sophisticated resonant soft x-ray scattering. Notably, we have observed a distinct preference for specific phase types depending on the length of the homologue. Longer homologues exhibit a predisposition towards the formation of tilted smectic phases, characterized by complex sequences of synclinic and anticlinic interfaces. Conversely, shorter homologues manifest a propensity for helical smectic structures. For intermediate homologues, the frustration is alleviated through the formation of several modulated smectic phases. Based on the presented research, we describe the preconditions for high level structures in relation with conflicting constraints.

cond-mat.soft↗

arXiv2023

Undulations of smectic A layers in achiral liquid crystals manifested as stripe textures

Self-assembly of organic molecules represents a fascinating playground to create various liquid crystalline (LC) nanostructures. In this work, we study layer undulations on micrometer scale in smectic A phases for achiral compounds, experimentally demonstrated as regular stripe patterns induced by thermal treatment. Undulations including their anharmonic properties are evaluated by means of polarimetric imaging and light diffraction experiments in cells with various thicknesses. The key role in stripe formation is played by high negative values of the thermal expansion coefficient.

cond-mat.soft↗

arXiv2023

Dimethylamino terminated ferroelectric nematogens revealing high permittivity

Since the recent discoveries, ferroelectric nematics became of upmost interest due to their outstanding ferroelectric properties. In this work, we prepared a series of polar molecules revealing a ferroelectric nematic phase (NF) with a very high dielectric constant (>104). A new motif, which differs from previously reported molecular structures, was optimized to support the NF phase. For all homologues the NF phase was observed directly on the cooling from the isotropic phase and ferroelectric behaviour was investigated by dielectric spectroscopy, second harmonic generation, polarization current measurements and by analysis of textures in the polarized light. The presented materials combine ferroelectricity with giant permittivity in a fluid media at room temperatures, so they appear to be extremely attractive. Polarity of molecules with the strong susceptibility to the electric field represent high potential for various applications in energy-efficient memory devices or capacitors.

physics.app-ph↗