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    Wyświetlanie 1-9 z 9
    Tytuł:
    Polymorphism and Initial Structure Modelling of a New Mesogen 9OSBch
    Autorzy:
    Kosyl, M.
    Zając, W.
    Ossowska-Chruściel, M.
    Chruściel, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399021.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.Eb
    64.70.M-
    Opis:
    We report the properties of a novel mesogen with high temperature cholesteric mesophase, which belongs to an unexplored as yet series of cholesteric esters. This compound is cholesteryl 4-(4-nonyloxybenzoylthio) benzoate ($C_9H_{19}OC_6H_4COSC_6H_4COOch$, where ch = cholesteryl), hereafter named 9OSBch. The chemical structure and purity of 9OSBch was established by $ \text{}^1 H$ NMR, $\text{}^{13} C$ NMR and FT-IR spectroscopy, and its mesomorphism was characterised by differential scanning calorimetry, polarizing optical microscopy, and transmitted light intensity. Differential scanning calorimetry measurements showed that substance is stable up to 270C and partially decomposes above this temperature. Observation under polarizing optical microscope revealed oily streak texture of cholesteric phase (Ch). The chemical structure of an isolated molecule was optimized by the density functional theory method. Energetically most favourable configuration is that of hockey stick geometry. At the same time this is the conformation best suited for the formation of highly ordered condensed phases.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 959-963
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Liquid Crystalline Polymorphism of Methyl and Ethyl trans-4-{[4-(alkanoyloxy)phenyl]diazenyl}benzoates
    Autorzy:
    Niezgoda, I.
    Galewski, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399011.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    64.70.M-
    61.30.Eb
    Opis:
    uthors present two new homologous series of liquid-crystalline compounds, methyl and ethyl 4-{[4-(alkanoyloxy)phenyl]diazenyl}benzoates, synthesis and investigation of their mesogenic properties. In the methyl series only nematic phase was detected and in the ethyl series nematic and smectic mesophases. Influence of the alkyl chain length on the phase transition temperatures and their entropic values are discussed and compared with literature data.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 926-932
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Monotropic Character of Polymorphism in Pentachloropyridine Crystal Studied by Calorimetric and Spectroscopic Methods
    Autorzy:
    Wójcik, G.
    Giermańsκa-Kahn, J.
    Marqueton, Y.
    Foulon, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1933583.pdf
    Data publikacji:
    1995-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    64.70.Kb
    78.30.-j
    Opis:
    Pentachloropyridine crystals in two polymorphic modifications: tetragonal and monoclinic were studied by differential scanning calorimetry and polarized IR and Raman spectroscopy in 20 to 200 cm$\text{}^{-1}$ region and at different temperatures from melting point down to the liquid nitrogen temperature. The 4 K difference in melting points of both forms indicates the occurrence of monotropy. The spectra were discussed in terms of positional disorder in the studied crystals which often happen to be mixtures of the monoclinic crystal and the L- and D-forms of the tetragonal one. The monotropic transition of the metastable tetragonal crystal into the stable monoclinic one was observed in the Raman spectra and under the polarizing microscope at temperatures ranging from 170 to 185 K and as an anomaly on the differential scanning calorymetry diagram at 193 K.
    Źródło:
    Acta Physica Polonica A; 1995, 88, 2; 339-347
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Liquid Crystalline Polymorphism of 4-Alkyloxybenzylidene-4-Alkyloxyanilines and Entropic Effects of Their Phase Transitions
    Autorzy:
    Godzwon, J.
    Sienkowska, M.
    Galewski, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1813170.pdf
    Data publikacji:
    2008-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    64.70.M-
    65.40.gd
    64.70.pp
    Opis:
    This paper summarizes liquid-crystalline polymorphism of the asymmetrical 4-alkyloxybenzylidene-4'-alkyloxyanilines. In this group, containing 121 compounds, 6 types of mesophases were detected: nematic, smectic A, smectic C, smectic B, smectic I, and smectic G. Influence of both alkyl chain length on the type of mesophases and entropic effects of phase transitions are discussed.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 4; 1145-1154
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Polymorphism Investigation of (4-(4-Octylobiphenyl)carboxylane) 4-(2-Methylobuthyl) Phenol Liquid Crystal Having Blue Phase
    Autorzy:
    Lewińska, G.
    Otowski, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/1538258.pdf
    Data publikacji:
    2010-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.Pq
    61.30.Eb
    64.70.M-
    42.70.Df
    Opis:
    (4-(4'-octylo-biphenyl)carbo-xylane) 4-(2-methylo-buthyl) phenol, the substance showing complex polymorphism, has been investigated using the calorimetric, microscopic and X-ray methods. This substance exhibited polymorphism during heating and cooling: a few smectic phases, a cholesteric phase and a blue phase as well. However, the substance polymorphism depends on the rate of heat flow. Existing of the blue phase has been confirmed by polarizing microscopic observations done at several temperature rates.
    Źródło:
    Acta Physica Polonica A; 2010, 117, 4; 562-565
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Solid State Polymorphism and Dynamics of 2,3-Dimethylbutan-2-ol (2,3-DM-2-B)
    Autorzy:
    Juszyńska, E.
    Massalska-Arodź, M.
    Zieliński, P.
    Krawczyk, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1418234.pdf
    Data publikacji:
    2012-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    65.40.-b
    65.40.Ba
    66.30.hp
    77.22.Gm
    Opis:
    In the paper we present adiabatic calorimetry and dielectric spectroscopy results for 2,3-dimethylbutan-2-ol (2,3-DM-2-B), one of the isomers of neohexanol. For 2,3-DM-2-B we have detected the following phase transitions: C2 (249.8 K) → C1 (262 K) → Is. No glass phase was found. In both crystalline phases C2 and C1 three relaxation processes were detected. These processes are discussed in relation to the calorimetric studies.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 4; 693-697
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Phonon Dispersion Analysis as an Indispensable Tool for Predictions of Solid State Polymorphism and Dynamic Metastability: Case of Compressed Silane
    Autorzy:
    Kurzydłowski, D.
    Grochala, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/1505181.pdf
    Data publikacji:
    2011-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.40.Vw
    63.20.dk
    64.70.K-
    81.30.-t
    Opis:
    Diamond anvil cell experiments suggest that upon compression above 26.5 GPa silane $(SiH_4)$ forms a polymeric phase VI, whose crystal structure has not yet been solved. Here we present DFT calculations showing how phonon-guided optimization leads to a polymeric Fdd2 structure which is the lowest-enthalpy polymorph of $SiH_4$ above 26.8 GPa, and which most probably can be identified as the experimentally observed polymeric phase. The new algorithm of predicting the lowest-energy structures enables simultaneous inspection of the potential energy surface of a given system, calculation of its vibrational properties, and assessment of chances for obtaining a metastable ambient-pressure structure via decompression. Our calculations indicate that at room temperature the differences in the vibrational and entropy terms contributing to the Gibbs free energy of different polymorphs of silane are negligible in comparison with corresponding differences in the zero-point energy corrections, in contrast to earlier suggestions. We also show that the Fdd2 polymorph should be metastable upon decompression up to 5 GPa, which suggests the possibility of obtaining a polymeric ambient-pressure form of $SiH_4$. Polymeric silane should exhibit facile thermal decomposition with evolution of molecular hydrogen and thus constitute an efficient (12.5 wt%) material for hydrogen storage.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 6; 895-900
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Solid State Polymorphism and Dynamics οf 2,2-Dimethylbutan-1-ol as Studied by Adiabatic Calorimetry and Dielectric Spectroscopy
    Autorzy:
    Juszyńska-Gałązka, E.
    Zieliński, P.
    Massalska-Arodź, M.
    Krawczyk, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399009.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    65.60.+a
    77.22.Gm
    64.70.P-
    Opis:
    2,2-dimethylbutan-1-ol, known as neohexanol, was studied by adiabatic calorimetry and dielectric spectroscopy. Details of complex solid state polymorphism and relaxational dynamics were identified and described. System of phases of neohexanol was found to be monotropic with three orientationally disordered crystalline phases besides isotropic liquid and ordered crystal. Moreover, two subsequent glass transition anomalies of heat capacity $C_{p}(T)$ were detected on heating in one of the supercooled orientationally disordered crystalline phases. Thermodynamical properties of neohexanol are described in relation to the dielectric relaxation processes found.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 917-925
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Polymorphism of Chiral Thioester Studied by Dielectric Spectroscopy
    Autorzy:
    Wawrzyniak, A.
    Chruściel, J.
    Douali, R.
    Dubois, F.
    Leblond, J.
    Legrand, Ch.
    Ossowska-Chruściel, D.
    Marzec, M.
    Ropa, P.
    Czerwiec, J.
    Wróbel, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399012.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    77.84.Nh
    64.70.M-
    77.22.Gm
    77.22.Ej
    Opis:
    (S)-(+)-4'-[(4-(1-methylheptyloxycarbonylphenyl) thiocarbonylphenyl]-decyloxybenzoate (in short 10.OPOSMH) was studied by complementary methods. The substance shows rich polymorphism. In addition to ferroelectric and antiferroelectric smectic C* phases it possesses three ferrielectric sub-phases. Phase transitions between the phases were revealed by differential scanning calorimetry and static dielectric permittivity measurements. The aim of this paper was to study phase transitions and differences in dielectric spectra shown by different phases. Collective and molecular dynamics of all phases shown by 10.OPOSMH will be discussed in terms of theoretical models. Dielectric spectra of antiferroelectric phase show two characteristic dielectric relaxation modes: one connected with the molecular process (reorientation around the short axis) and the other originating from fluctuations of antiferroelectric order parameters.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 933-936
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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