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1
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Intermolecular Interactions in Organic Dye Monolayers Formed by Langmuir-Blodgett Technique

100%
Bauman D.
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issue 4
525-531
EN
Langmuir and Langmuir-Blodgett films of some organic dyes (perylene-like dyes, derivatives of 4-amino-naphthali-mide, derivatives of naphthoylene-benzi-mida-zole, azo dyes) and their mixtures with thermotropic liquid crystal or arachidic acid have been investigated. Surface pressure as a function of the mean molecular area for the Langmuir films were measured and information about organization of molecules at the air-water interface has been obtained. Absorption spectra in situ for the Langmuir films and both absorption and fluorescence spectra for Langmuir-Blodgett films were recorded. The results obtained from spectroscopic studies have led to conclusions about formation of self-aggregates of dye molecules, both in ground and excited states, at the phases interfaces.
2
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Molecular Interactions in Monolayers οf Azo Dye/Liquid Crystal Mixtures at Interfaces

51%
Bauman D., Płóciennik A., Inglot K.
Acta Physica Polonica A
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2009
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vol. 116
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issue 2
203-210
EN
A study of azo dye/liquid crystal mixtures in monolayers formed at an air-water interface (the Langmuir films) and at a solid surface (the Langmuir-Blodgett films) has been performed. Five azo dyes with various molecular structure and the liquid crystal 4-octyl-4'-cyanobiphenyl (8CB) have been used. The dyes have been added to the liquid crystal at various molar fractions. Surface pressure and surface potential versus mean molecular area isotherms for the Langmuir films have been recorded and information about intermolecular interactions at the air-water interface has been obtained. On the basis of electronic absorption measurements for the Langmuir and Langmuir-Blodgett films the conclusions about the ability of dyes molecules to form self-aggregates at the interfaces have been drawn. The influence of the dye molecular structure and its concentration on aggregates' geometry has been found.
3
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Optical Order Parameter of Dichroic Azo-Dyes in Liquid Crystalline Side-Chain Polysiloxanes

51%
Chrzumnicka E., Bauman D., Jadżyn J.
Acta Physica Polonica A
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2002
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vol. 102
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issue 6
767-780
EN
Polarized light absorption spectra of seven dichroic azo-dyes dissolved in mesogenic side-chain polysiloxanes were recorded as a function of temperature. On the basis of the spectra the optical order parameter of the dyes was determined. The influence of the dye on the phase transition temperatures of polysiloxanes was examined. The results obtained for polysiloxanes were compared with the data for low molecular weight liquid crystal.
4
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Guest Effect on Nematic-Isotropic Phase Transition Temperature of Liquid Crystal 6CHBT

51%
Bauman D., Solczyński J., Chrzumnicka E.
Acta Physica Polonica A
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1997
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vol. 92
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issue 6
1151-1161
EN
The polarized absorption spectra of seven dichroic azo dyes dissolved in the nematogenic liquid crystal host 6CHBT have been recorded as a function of temperature. On the basis of these spectra, the guest order parameter has been determined. Moreover, the influence of the dye addition on the behaviour of the guest-host mixture in the vicinity of the nematic- isotropic phase transition has been examined. The experimental results have been compared in some details with the calculations done on the basis of the mean field theory for binary mixtures.
5
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Orientational Behaviour of the Guest-Host Systems in the Smectic A and Nematic Phases

51%
Bauman D., Moryson H., Wolarz E.
Acta Physica Polonica A
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1992
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vol. 81
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issue 4-5
559-570
EN
The measurements of the polarized absorption and fluorescence components spectra for the guest-host mixtures have been used to study the long orientational order in the uniaxial phases of the liquid crystal. The temperature dependence of the order parameters, ⟨P_{2}⟩ and ⟨P_{4}⟩, has been investigated and the molecular distribution function has been determined. On the basis of the ⟨P_{2}⟩ and ⟨P_{4}⟩, values some conclusions about the molecular orientation in the smectic A and nematic phases of the liquid crystalline samples have been drawn. It has been also found that the fluorescence spectroscopy is a sensitive method for determination of the phase transition temperatures of the liquid crystal doped with the fluorescent dye.
6
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Prenematic Self-Assembling of Mesogenic Molecules in Isotropic Liquid and Orientational Order in Nematic Phase

51%
Wolarz E., Bauman D., Jadżyn J., Dąbrowski R.
Acta Physica Polonica A
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2011
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vol. 120
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issue 3
447-454
EN
Dielectric relaxation study of nematogenic 4-n-alkyl-4'-cyanobiphenyls (nCB, n = 5, 6), 4-(trans-4'-n-alkylcyclohexyl)isothiocyanatobenzenes (nCHBT, n = 6, 8), 4-cyanophenyl-4'-n-alkylbenzoates (nCPB, n = 6, 8), 4-cyano-3-fluorophenyl-4'-n-octyloxybenzoate (8OCFPB), and 4-cyanophenyl-4'-n-octyloxy-3'-fluorobenzoate (8OCPFB) was performed in the frequency range from 50 kHz to 100 MHz in the nematic and isotropic phases. The static permittivity and the relaxation process related to the rotation of molecules around their short axis was analyzed. For some of these liquid crystals anomalous temperature dependence of static permittivity in the pretransitional region of the isotropic phase was observed. Based on the Meier-Saupe-Martin model of molecular diffusion in nematics, the orientational order parameter 〈P_2〉 was determined from dielectric relaxation times and retardation factor. The values of 〈P_2〉 calculated from the dielectric relaxation data were compared with the results obtained from measurements of polarized electronic absorption. Correlations between the magnitude of the dielectric pretransitional effect and the orientational order in the nematic phase were discussed.
7
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Guest Influence on the Dipolar Association of the Nematic Liquid Crystal Host

51%
Bauman D., Fan Z.-X., Haase W.
Acta Physica Polonica A
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1991
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vol. 80
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issue 4
545-552
EN
X-ray diffraction method has been used to study the molecular organization in 4-n-pentyl-4'-cyano-p-terphenyl doped with guest dye molecules. It has been found that the dye with strong polar end group affects significantly the monomer to dimer ratio in the nematic phase of the liquid crystal studied.
8
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Guest-Host Interactions in Nematic p-Cyano-p'-Alkylphenylcyclohexanes

51%
Bauman D., Moryson H., Jadżyn J.
Acta Physica Polonica A
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1994
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vol. 85
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issue 3
553-562
EN
Studies of the temperature dependence of the guest order parameter for binary mixtures of the dichroic azo dye in the homologous series of the p-cyano-p'-alkylphenylcyclohexane were performed. Odd-even effect for the order parameter value was observed. A correlation between the shift in the nematic-isotropic transition temperature after dye addition and the orientation of the guest molecules in the nematic host was discussed.
9
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Molecular Dynamics of 4-(trans-4'-n-Heptylcyclohexyl)- Isothiocyanatobenzene Studied with Dielectric Relaxation Spectroscopy

45%
Bauman D., Czechowski G., Jadżyn J., Legrand C., Douali R.
Acta Physica Polonica A
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2000
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vol. 98
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issue 1-2
71-81
EN
Dielectric relaxation study was carried out for the nematic and isotropic phases of 4-(trans-4'-n- heptylcyclohexyl)isothiocyanatobenzene in the frequency range from 100 kHz to 1 GHz. In the nematic phase two relaxation processes were recorded for the electric permittivity component measured parallel to the molecular orientation (director n) and three relaxation processes - for the perpendicular permittivity component. The strength of the nematic potential and the nematic order parameter were estimated.
10
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Preparation and Characterization of Two-Dimensional Ordered Arrays of Metallic Nanoparticles

45%
Kandulski W., Kosiorek A., Rybczyński J., Bauman D., Giersig M.
Acta Physica Polonica A
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2003
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vol. 104
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issue 5
495-502
EN
A method of obtaining large-scale 2D arrays of ordered metallic nanoparticles is presented. The arrays were prepared using nanosphere lithography based on the self-assembly of latex particles on a water surface. Using 496 nm and 1040 nm diameter particles, it was possible to prepare arrays of over one cm^2, with defect-free areas of over 50μ m^2. By the evaporation of nickel or gold, periodic metallic particle arrays were produced. Modification of the particle array morphology was also shown by using double-layered masks. Computer simulated mask models were used to reveal interesting morphologies obtainable by the application of multilayered masks.
11
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Anomalous Dielectric Relaxation in Binary Mixtures of Mesogenic Solvent/Non-Mesogenic Solute

45%
Jadżyn J., Bauman D., Déjardin J., Ginovska M., Czechowski G.
Acta Physica Polonica A
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2005
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vol. 108
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issue 3
479-489
EN
Dielectric relaxation studies for mixtures of strongly polar and mesogenic n-heptylcyanobiphenyl with non-polar and non-mesogenic carbon tetrachloride (CCl_4) were performed. The absorption band broadening due to fractional diffusion was observed. A correlation between the non-mesogenic admixture concentration and the anomalous diffusion exponent was found.
12
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Dielectric and Optical Studies of Homologous Series of Bicyclo[2,2,2]octane Derivatives with -NCS Terminal Group

39%
Herba H., Żywucki B., Czechowski G., Bauman D., Wąsik A., Jadżyn J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 6
985-994
EN
The static dielectric constants and the optical birefringence for four members of the homologous series of bicyclo[2,2,2]octane derivatives with -NCS terminal group (pentyl to octyl) have been measured as a function of temperature. From the dielectric anisotropy, the optical birefringence as well as the polarized absorption spectra of the dichroic dye dissolved in the liquid crystalline host the order parameter has been determined. The results obtained by using various experimental methods have been compared with those calculated from the Maier-Saupe mean field theory. It has been found that the order parameter for the successive homologues shows alternation similar to that exhibited for the nematic-isotropic transition temperature.
13
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Comparative Study of Orientational Order of Some Liquid Crystals from Various Homologous Series

39%
Bielejewska N., Chrzumnicka E., Mykowska E., Przybylski R., Szybowicz M., Władysiak K., Bauman D.
Acta Physica Polonica A
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2006
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vol. 110
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issue 6
777-793
EN
The long-range orientational order of liquid crystals from homologous series of 4-n-alkyl-4'-cyanobiphenyl, 4-n-alkoxy-4'-cyanobiphenyl, trans-4-n-alkyl(4'-cyano-phenyl)-hexane, and 4-(trans-4'-n -alkylcyclohexyl)-isothiocyanato-benzene was studied by means of classical methods of optical spectroscopy: absorption of the polarized light, fluorescence depolarization, and Raman scattering depolarization. The absorption, emission, and Raman scattering spectra of linearly polarized light were recorded as a function of temperature in the whole range of the mesophase. On the basis of these spectra the order parameters ⟨P_2⟩ and ⟨P_4⟩ as well as the orientational distribution function were determined. The results obtained for members of various series with the same number of carbon atom in the alkyl chain were compared. It was found that the orientational order of liquid crystal molecules depends on the structure of the rigid core, on the kind of the terminal group as well as on the alkyl chain length. The odd-even effect for the order parameters, explained as the alteration of interaction between alkyl chains, was observed.
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