Publications by authors named "Maria Massalska-Arodz"

This article presents the molecular dynamics and solidification behavior of a 2,3-difluoro-4-propylphenyl 2,3-difluoro-4-(4-pentylcyclohexyl)benzoate nematic liquid crystal (5C4FPB3) observed by broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC). Polarized optical microscopy (POM) is also performed to confirm the phase transition temperatures. Our investigation reveals rare crystallization of the orientationally disordered crystal (ODIC) phase from the nematic phase and a glass transition of the crystal at cooling rates higher than 1 K min-1.

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The chiral nematic S,S-2,7-bis(4-pentylphenyl)-9,9-dimethylbutyl9H-fluorene (5P-AmFLAm-P5) liquid crystal shows a complex phase diagram strongly dependent on thermal treatment as identified by Polarizing Optical Microscopy (POM) and differential scanning calorimeter (DSC). The molecular dynamics in various thermodynamics states was studied by means of broadband dielectric spectroscopy (BDS). The vitrification of a chiral nematic phase (N) is manifested by a Vogel-Fulcher-Tammann (VFT)-type temperature dependence of structural relaxation time ([Formula: see text]).

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This article presents the crystallization behavior and molecular dynamics of the supercooled nematic state of the newly synthesized liquid crystal 2,7-bis(4-pentylphenyl)-9,9-diethyl-9 H-fluorene (5P-EtFLEt-P5) studied by means of broadband dielectric spectroscopy (BDS). 5P-EtFLEt-P5 is a fragile glass-forming system with a high fragility parameter ( m ≈ 121). The study compares the isothermal melt- and cold-crystallization processes at several selected temperatures T in the vicinity of the glass-transition temperature T (1.

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2,2-Dimethylbutan-1-ol (2,2-DM-1-B), 3,3-dimethylbutan-1-ol (3,3-DM-1-B), and 3,3-dimethylbutan-2-ol (3,3-DM-2-B) show a rich solid-state polymorphism, which includes one or more plastic crystalline phases (also referred to as orientationally disordered crystalline (ODIC) phases) and glass of the liquid or ODIC phases. In this work, the dynamics of the three isomeric alcohols was investigated in the liquid and plastic crystalline phases by fast field cycling H NMR relaxometry in the temperature range between 213 and 303 K. The analysis of the nuclear magnetic relaxation dispersion curves (i.

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Polymorphism and molecular dynamics of ethosuximide with molecules of left- and right-handed chirality have been studied in detail using dielectric spectroscopy. Density functional theory calculations of molecular conformations and dimer formation were performed to aid the interpretation of measurements. Moving window correlation analysis of the imaginary part of dielectric permittivity spectra allowed us to complete the monotropic system of phases found by the differential scanning calorimetry method.

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Single-crystal structural analyses and heat capacity measurements were performed on two Schiff base liquid crystal compounds, 5CBAA (4-chlorobenzylidene-4'-pentyloxyaniline) and 5ABCA (4-pentyloxybenzylidene-4'-chloroaniline). The alkyloxy-chain of a 5CBAA molecule was conformationally ordered in the crystal at room temperature. While that of 5ABCA was partially disordered in the room temperature phase but ordered in a low-temperature phase at 100 K.

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The molecular dynamics of 4-n-butyloxybenzylidene-4'-n'-octylaniline (BBOA, abbreviated also as 4O.8) was studied by broadband dielectric spectroscopy (BDS) for samples that were exposed to various thermal treatments. Phase transitions between liquid crystalline phases (N, SmA, SmB, and SmB) were evidenced by abrupt changes in the temperature dependence of the dielectric permittivity spectra and dielectric relaxation times.

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(1)H NMR relaxometry was applied to investigate dynamic processes in the isotropic liquid, cholesteric, and crystalline phases of the chiral mesogen 4'-butyl-4-(S)-(2-methylbutoxy)azoxybenzene (4ABO5*). To this aim, (1)H longitudinal relaxation rates were measured as a function of temperature (between 257 and 319 K) and Larmor frequency (from 10 kHz to 35 MHz by a fast field-cycling relaxometer and at 400 MHz by an NMR spectrometer). The NMR relaxation dispersion (NMRD) curves so obtained were analyzed in terms of models suitable for the description of dynamic processes in the different phases, thus quantitatively determining values of characteristic motional parameters.

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Based on new diffraction data from aligned samples of smectic E (SmE) phase of 4-n-alkyl-4'-isothiocyanato-1,1'-biphenyls, systematics against the alkyl chain length n is analyzed. In order to perform the analysis, the molecular form factor approximated by a box-shaped distribution is calculated while taking the rounding of the distribution at corners into account. The analysis clearly shows the nano-segregated layered structure, which does not fit to the traditional structural view of SmE phase but does fit to the model the present authors proposed recently.

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The FT-IR spectra of the 4-bromobenzylidene-4'-alkyloxyanilines (nBBAA, for n = 4-12) were studied as a function of temperature. The molten state of the alkyloxy chain in smectic B (SmB), smectic A (SmA), and isotropic phases was analyzed. Generalized two-dimensional (2D) correlation spectroscopy has been applied to study changes in the conformational structure and specific interactions of molecules at phase transition in homologous series of nBBAA.

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Thermodynamic and diffraction analyses were performed to establish the phase diagram for a binary system between 4-n-nonyl-4'-isothiocyanatobiphenyl (9TCB) and n-nonane. The swollen SmE structure is identified in the binary system. Upon swelling, a characteristic two-dimensional herringbone array is maintained whereas the layer spacing of SmE structure increases with the content of n-nonane.

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For 4-cyano-3-fluorophenyl 4-butylbenzoate, a glass former giving glass of nematic phase at ambient pressure and after rapid pressurizing, isothermal studies of complex dielectric permittivity vs pressure were performed near room temperature. In the previous isobaric experiment, on cooling the nematic phase two super-Arrhenius α relaxations, ascribed to the reorientations of molecules around short axes (main process) and precession of long molecular axes, and β relaxation related to intramolecular motions were found. In the present isothermal experiments nematic-smectic phase transition was induced by increasing pressure.

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To confirm the molten state of the alkyl chain in soft crystalline phase, smectic E (SmE) phase, thermodynamic and spectroscopic analyses were performed on 4-n-alkyl-4'-isothiocyanatobiphenyl (nTCB, n: the number of carbon atoms in the alkyl group). DSC results of 11TCB and 12TCB, having extra smectic A phase besides smectic E phase, show that their chain-length dependence of entropies of transition (Δ(trs)S) from the ordered crystalline (OC) phase to the SmE phase matches the trend found for nTCB (n = 4-10), while no chain-length dependence is observed in Δ(trs)S at the SmE-to-SmA and SmA-to-isotropic liquid (IL) phase transitions in 11TCB and 12TCB. Temperature dependences of FT-IR spectra of six compounds (n = 2, 3, 5, 8, 10, and 12) were recorded.

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The results of adiabatic calorimetry, mid-infrared spectroscopy, X-ray diffraction, and polarized microscopy of 4-hexyl-4'-isothiocyanatobiphenyl are presented. Apart from the well-known isotropic liquid and smectic phases, calorimetric measurements indicate the existence of two stable crystalline phases. Quantitative analysis of infrared bands enabled the determination of phase transitions, observation of crystallization kinetics, and elucidation of the glass transition of the crystal-like smectic E phase.

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The results of mid-infrared spectroscopy and X-ray studies of the third member of the 4-n-alkyl-4'-isothiocyanatobiphenyl (nTCB) homologous series are presented. Correspondence between the phase transitions observed by means of the IR spectroscopy and those given by the adiabatic calorimetry was found. The structure of five solid phases was obtained by X-ray measurements.

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Molecular dynamics and resulting disorder in the soft crystal, smectic E (SmE) phase, were studied in detail for the title compound, 4-butyl-4'-isothiocyano-1,1'-biphenyl (4TCB), by (1)H NMR spectroscopy and adiabatic calorimetry. The ordered crystal phase of 4TCB was realized for the first time under ambient pressure after long two-step annealing and used as the reference state in the analysis of the experimental results. Four motional modes were identified in the SmE phase through the analysis of the (1)H NMR T(1).

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