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Molecular Dynamics of Tert-butyl Chloride Confined to CPG (7.4, 15.6 nm)

100%
Szutkowska L., Peplińska B., Jurga S.
Acta Physica Polonica A
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2005
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vol. 108
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issue 2
357-370
EN
The paper complements our earlier NMR investigation of molecular dynamics of tert-butyl chloride restricted by geometries of the type MCM-41 and CPG by the new sizes of CPG and by differential scanning calorimetry method. We report proton and deuteron NMR lineshapes and the spin-lattice relaxation results of tert-butyl chloride in CPG of the 15.6 nm and 7.4 nm pore diameter in the temperature range 70 K≤ T≤ 292 K. The bulk-like component of the confined tert-butyl chloride, in temperatures corresponding to phase III, is interpreted as a composition of two dynamically different subphases. The parameters of motions of both subphases are derived. The tert-butyl group motion in both subphases is more restricted than in the bulk tert-butyl chloride, although the activation energies are lower. Differential scanning calorimetry was used to determine temperatures of the phase transitions (140 K≤T≤292 K). The results show that the depression of the phase transition temperature is pore size dependent and that the confinement has less influence on transition to the plastic phase than on the freezing and on the solid II - solid III transition.
2
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Spectroscopic Studies of Poly(ε-Caprolactone)/Sodium Montmorillonite Nanocomposites

100%
Krzaczkowska J., Fojud Z., Kozak M., Jurga S.
Acta Physica Polonica A
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2005
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vol. 108
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issue 1
187-196
EN
Polymer-layered silicate nanocomposites belong to a new class of hybrid materials consisting of organic-synthetic polymer matrix and inorganic filler-layered structure clay minerals. The paper presents the results of FTIR, NMR, and SAXS studies of poly(ε-caprolactone)/sodium montmorillonite nanocomposites. We observed a correlation between the concentration of poly(ε-caprolactone) in nanocomposite samples and structural changes both of the clay mineral and the intercalated polymer. Stiffening of the clay structure appears as a result of poly(ε-caprolactone) intercalation into a clay structure. ^{27}Al NMR studies indicated in nanocomposites two non-equivalent sites of aluminium ions, i.e. in octahedral and tetrahedral coordination, whereas in the montmorillonite clay structure the aluminium ions are located in the interlayer space too. We found also that the temperatures of structural changes and softening process of poly(ε-caprolactone) chains in the nanocomposites depend on the concentration of poly(ε-caprolactone).
3
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^1H NMR and Rheological Studies of the Calcium Induced Gelation Process in Aqueous Low Methoxyl Pectin Solutions

100%
Dobies M., Kuśmia S., Jurga S.
Acta Physica Polonica A
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2005
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vol. 108
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issue 1
33-46
EN
The ^1H NMR relaxometry in combination with water proton spin-spin relaxation time measurements and rheometry have been applied to study the ionic gelation of 1% w/w aqueous low methoxyl pectin solution induced by divalent Ca^{2+} cations from a calcium chloride solution. The model-free approach to the analysis of ^1H NMR relaxometry data has been used to separate the information on the static (β) and dynamic (〈τ_c〉) behaviour of the systems tested. The ^1H NMR results confirm that the average mobility of both water and the pectin molecules is largely dependent on the concentration of the cross-linking agent. The character of this dependency (β,〈τ_c〉 and T_2 vs. CaCl_2 concentration) is consistent with the two-stage gelation process of low methoxyl pectin, in which the formation of strongly linked dimer associations (in the range of 0-2.5 mM CaCl_2) is followed by the appearance of weak inter-dimer aggregations (for CaCl_2 ≥ 3.5 mM). The presence of the weak gel structure for the sample with 3.5 mM CaCl_2 has been confirmed by rheological measurements. Apart from that, the T_1 and T_2 relaxation times have been found to be highly sensitive to the syneresis phenomenon, which can be useful to monitor the low methoxyl pectin gel network stability.
4
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Wetting of Nanostructurized Sapphire and Gold Surfaces

100%
Kempiński M., Jenczyk J., Jurga S., Śliwińska-Bartkowiak M.
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EN
We present the results of preliminary experiments regarding research on the contact angle measurements of various liquids on solid surfaces with different morphology. The aim was to get insight into the dependence of wetting phenomena on the nanoscale surface roughness. Flat and nanostructurized surfaces of gold and sapphire were used in the experiments. Four liquids - bromobenzene, water, mercury, and gallium - covering a broad range of surface tension values were used to check how varying roughness influences wetting in the systems with different adhesion/cohesion ratio. Structurization was anisotropic, which resulted in the very interesting behaviour of the examined liquids on the selected surfaces. Significant change of the wetting properties was observed as well as a strong dependence on the surface morphology.
5
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Molecular Dynamics in Cyclic Olefin Copolymer

88%
Makrocka-Rydzyk M., Orozbaev B., Nowaczyk G., Głowinkowski S., Jurga S.
Acta Physica Polonica A
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2005
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vol. 108
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issue 2
385-393
EN
Nuclear magnetic resonance, broadband dielectric spectroscopy and dynamic-mechanical thermal analysis were employed to study molecular dynamics of ethylene-norbornene copolymer. The analysis of experimental data indicates existence of three motional processes denoted asαβ, andγ in order of decreasing temperature. Theα relaxation is related to the dynamic glass transition, while theβ relaxation, observed only for the untreated sample, is assigned to short range segmental motions involving norbornene units. Theγ relaxation is due to very local motions of ethylene units e.g. trans-gauche isomerization, similar to those responsible forγ relaxation in polyethylene. The rate of motion accountable for γ process, follows the Vogel-Fulcher-Tammann equation, similarly to α transition, indicating cooperative nature of the motion.
6
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EPR and Impedance Measurements of Graphene Oxide and Reduced Graphene Oxide

88%
Kempiński M., Łoś S., Florczak P., Kempiński W., Jurga S.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
81-85
EN
We report the observations of electron paramagnetic resonance and impedance measurements of graphene oxide and reduced graphene oxide performed in the wide temperature range in order to get insight into the electronic properties of graphene-based materials and the role of oxygen functionalities in the charge carrier transport phenomena. In such systems the strong spin localization, hopping charge carrier transport as well as the formation of adsorption layers are observed, all the phenomena changing significantly after the heavily oxidized graphene is reduced.
7
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Structural Studies of Selected DSPC-Surfactant Model Systems of Biological Membranes

76%
Szpotkowski K., Kozak M., Kozak A., Zieliński R., Wieczorek D., Jurga S.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
561-564
EN
Fourier transform infrared spectroscopy was used to analyse the influence of a cationic surfactant from the group of morpholine derivatives on the conformational dynamics of CH_2 group in acyl chain of DSPC. The presence of the surfactant causes a decrease in the DSPC phase transition temperature. This result suggests that the surfactant interactions with phospholipid molecules disturb the lipid layers. The Fourier transform infrared measurements were supplemented with tests of the environmental toxicity of the surfactant used.
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