arXiv subjects

Ewa Juszyńska-Gałązka

Publications and source records attributed to Ewa Juszyńska-Gałązka.

7 recordsLinked to original sources

arXiv2026

Competing crystallization pathways and cold crystallization kinetics in 10OS5 liquid crystal

The liquid crystalline 4-pentylphenyl-4'-decyloxythiobenzoate is investigated in various temperature programs for determination of crystallization kinetics and glassforming properties. The Avrami model, Augis-Bennett method and isoconversional method are used. Cooling at the 25-30 K/min rate results in formation of the glass of the tilted smectic Y phase with the herring-bone order within layers. Slower cooling leads to the partial or total (2 K/min) crystallization of the metastable Cr2 phase, which during subsequent heating or annealing in a proper temperature transforms to another Cr1 phase. Heating from the vitrified smectic Y leads to cold crystallization of the pure Cr1 phase or the Cr1/Cr2 mix. Both Cr1 and Cr2 are conformationally disordered crystal phases, which is indicated both by the melting entropy values and the dielectric spectra. The results demonstrate that the energy released during cold crystallization can be tuned by thermal history, highlighting 10OS5 as a candidate for thermal energy storage applications.

cond-mat.mtrl-sci↗

arXiv2026

Ternary liquid crystalline mixture showing broad antiferroelectric smectic C$_A$* and glassy hexatic smectic X$_A$* phases

A ternary liquid crystalline mixture was designed to obtain a tilted hexatic smectic phase in the glassy state. Structural, electro-optic, and dielectric properties of the mixture are investigated, and selected measurements are also performed for its pure components. In particular, the electron density profile perpendicular to smectic layers is determined from the X-ray diffraction data and compared to the results of density functional theory calculations both for the mixture and pure components. Comparison of the experimental smectic layer spacing and tilt angle in the mixture allows us to assess whether molecular dimerization is likely to occur. On the mesoscopic scale, the helical pitch is determined in the SmC$_A$* phase of the mixture, and selective reflection of light is observed under a polarizing microscope in the SmC*, SmC$_A$*, and SmX$_A$* phases. The glass transition in the smectic X$_A$* phase is observed in calorimetric results. At the same time, the dielectric spectra do not directly reveal the primary $α$-process, although the secondary $β$- and $γ$-processes are detected. Overall, the results show that the ternary mixture stabilizes a broad SmC$_A$* phase and enables vitrification of the hexatic SmX$_A$* phase, while the structural data suggest a change in the molecular organization between the SmC* and SmC$_A$* phases.

cond-mat.soft↗

arXiv2026

Selective reflection of light in glassforming ternary liquid crystalline mixtures

Two ternary liquid crystalline mixtures are formulated and investigated by differential scanning calorimetry, polarizing optical microscopy, X-ray diffraction, and broadband dielectric spectroscopy. Paraelectric smectic A*, ferroelectric smectic C*, and antiferroelectric smectic C$_A$* phases are detected. The glass of the smectic C$_A$* phase is formed at moderate cooling rates. Vitrification prevents the approaching transition to a hexatic smectic phase. One mixture shows a strong thermochromic effect in the smectic C$_A$* phase and selectively reflects blue light in the glassy state. Both mixtures reflect either green or red light in the smectic C* phase, depending on temperature treatment: whether the sample is cooled or heated, or at which rate the temperature changes.

cond-mat.soft↗

arXiv2025

Low-temperature structural study of smectic C$_A$* glass by X-ray diffraction

The liquid crystalline compound, forming the glass of the smectic C$_A$* phase, is investigated by the X-ray diffraction in the 18-298 K range. The characteristic distances within the smectic C$_A$* phase are determined. The electron density profile along the smectic layer normal is inferred and compared with the results of the density functional theory calculations. Observations of the selective reflection of the visible light investigate the helical ordering within the smectic C$_A$* glass. The results indicate slow evolution of the smectic layer spacing, intermolecular distances, and electron density distribution below the glass transition temperature. Meanwhile, the relative range of the short-range order within the smectic layers and the helix pitch are relatively constant in the glassy state.

cond-mat.soft↗

arXiv2025

Glassforming liquid crystalline equimolar mixtures of MHPOBC and fluorinated compounds -- structural, optical, and dielectric properties

Three liquid crystalline equimolar mixtures are formulated, each containing the MHPOBC compound and the homolog from the 3FmHPhF6 series with m = 4, 5, and 6. The properties of the mixtures are investigated by differential scanning calorimetry, polarizing optical microscopy, X-ray diffraction, electro-optic measurements, and UV-Vis-NIR and dielectric spectroscopies. In all mixtures, the smectic A*, smectic C*, and smectic C$_A$* phases are observed. Each mixture can be supercooled and forms the glass of smectic C$_A$* at 225-238 K. The glass transition temperature decreases with the increasing C$_m$H$_{2m}$ chain length in the 3FmHPhF6 molecule. The tilt angle in the smectic C$_A$* phase reaches 36.5-37.5°. The selective reflection of light in the visible and near-infrared spectral ranges is observed, with a strong dependence of the reflected light's wavenumber on temperature.

cond-mat.soft↗

arXiv2024

Crystallization kinetics of equimolar liquid crystalline mixture and its components

The new equimolar mixture comprises liquid crystalline compounds MHPOBC and partially fluorinated 3F2HPhF6. The phase sequence of the mixture is determined by differential scanning calorimetry, polarizing optical microscopy, X-ray diffraction, and broadband dielectric spectroscopy. The enantiotropic smectic A*, C*, and CA* phases are observed for the mixture. Only partial crystallization of the mixture is observed during cooling at 2-40 K/min and the remaining smectic CA* phase undergoes vitrification. In contrast, the crystallization of the pure components is complete or almost complete for the same range of cooling rates. The kinetics of the non-isothermal and isothermal crystallization of the mixture and pure components are investigated by differential scanning calorimetry. The non-isothermal data are analyzed by the isoconversional method, while the isothermal data are analyzed using the Avrami model. Typically, the nucleation-controlled crystallization kinetics are observed.

cond-mat.soft↗

arXiv2022

Tuning magnetostructural phase transition in CoMn$_{0.88}$Cu$_{0.12}$Ge by application of hydrostatic pressure

Structural and magnetic properties of the CoMn$_{0.88}$Cu$_{0.12}$Ge compound have been investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) accompanied with investigation of magnetic properties under applied hydrostatic pressure up to 12 kbar. It has been found that the orthorhombic crystal structure of the TiNiSi-type, which is dominant at low temperatures, turns into the hexagonal Ni$_2$In-type one, slightly above 200 K. The structural transition is of the first-order type as confirmed by presence of distinct thermal hysteresis exceeding 20 K. The ac magnetic measurements indicate a ferromagnetic order below the Curie temperature $T_C$ of 238 K, followed by additional anomaly at lower temperatures - the latter one being related to the structural transition. Application of hydrostatic pressure leads to temperature separation of the purely magnetic transition, whose Curie temperature $T_C$ slowly increases with applied pressure, and the magnetostructural transition characterized by critical temperature showing much rapid decrease with increasing pressure. Comparison of the DSC data for the investigated compound and the isostructural CoMn$_{0.95}$Cu$_{0.05}$Ge one has made it possible to determine both the structural and magnetic components of entropy change.

cond-mat.mtrl-sci↗