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od 2020-09-20 |
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Morphology and NMR self-diffusion in PBA/PEO miktoarm star copolymers Morphology and NMR self-diffusion of two miktoarm star copolymers differing in fraction of poly(n-butyl acrylate) and poly(ethylene oxide) (PBA and PEO) arms were under investigation. Structural characteristics of copolymers was obtained on the basis of Small Angle X-Ray Scattering (SAXS) investigations. The phase separated nanoscale morphology of the miktoarm star copolymer with a high fraction of PEO arms was confirmed by Scanning Probe Microscopy (SPM) studies. The modified Avrami approach was used to obtain the information on the non-isothermal crystallization kinetics of the studied systems. It was observed that the crystallization in the system with a higher content of PBA, occurring at higher undercooling, was characterized by a higher crystallization rate. It was also found that increase in PBA arms fraction leads to the reduction in the size of PEO domains. The activation energy of the crystallization process, estimated with Kissinger's method, is lower for miktoarm star copolymer with higher PBA content, which results from facilitation of the transport of PEO chains in the direction of the growing crystal due to the presence of mobile PBA arms. The self-diffusion studies of miktoarm star copolymers melts, carried out with the Pulsed-Gradient STimulated-Echo (PGSTE) Nuclear Magnetic Resonance (NMR) technique, reveals the existence of at least two types of diffusion mechanisms in these systems.
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Zeitschrift für Physikalische Chemie, 226, 1271-1292, (2012) |
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DSC and spectroscopic studies of disulfiram radiostability in the solid state The effect of ionising radiation on the physicochemical properties of disulfiram (Antabuse, Esperal, bis-diethylthiocarbamoil disulphide) has been studied by DSC, FTIR, EPR, MS, TLC and HPLC. Sterilisation was carried out in the solid state, at room temperature and normal air humidity using the electron beam of 9.96 Mev from accelerator. All the measurements were made simultaneously for the irradiated and nonirradiated substance. It has been found that the drug studied in solid phase when subjected to an electron beam corresponding to the irradiation in the doses 10-100 kGy shows the presence of free radicals (EPR), and a change in colour from white to pale green-grey that disappears after solution in water or methanol. After the irradiation with the dose of 100 kGy, its melting point and enthalpy slightly decreased. Also the content of the active substance decreases (HPLC -1.5%, UV -3.6%, iodometric titration method -2.7%) and trace amounts of the radiolysis products appear (HPLC). The substance irradiated with the doses 10-50 kGy does not show changes in the melting point, in the content and presence of the radiolysis products. The EPR results have shown that free radicals disappear after about a year and the discolouring disappears with them. The results of this study have shown that disulfiram can be subjected to sterilisation by irradiation with no deterioration of its physico-chemical properties, but a long time of storage needed to remove free radicals and discolouration questions the economic justification for this type of sterilisation.
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Journal of Thermal Analysis and Calorimetry, 108(1), 33-40, (2012) |
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Thermoplastic polyurethane/(organically modified montmorillonite) nanocomposites produced by in situ polymerization A series of polyurethane nanocomposites were synthesized from thermoplastic polyurethanes (with different hard segment ratios) and two types of organically modified montmorillonites (OMMT) - Cloisite (R) 10A and Cloisite (R) 20A. The thermal behavior was examined by non-isothermal thermogravimetry (TG, DTG), Differential Scanning Calorimetry (DSC) and Dynamic-Mechanical Thermal Analysis (DMTA). The results of X-ray analyses showed that the OMMT produced the intercalated polyurethane nanocomposites. It has been proven that the thermal stability and tensile properties of these new systems were higher when the organoclay was present within the polymer matrix. Moreover, these properties depend on both the OMMT loading and the type of gallery cations of the organically modified montmorillonites.
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Express Polymer Letters, 6(8), 610-619, (2012) |
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Structural changes of DPPC bilayers induced by gemini surfactant The phospholipid-gemini surfactant systems are promising agents for construction of lipoplexes for DNA delivery systems in gene therapy. In this work the influence of a gemini surfactant - 1,1'-(1,6-hexan)bis3-octyloxymethylimidazolium di-chloride) (IMI_C1_C6_C8) on the structure and phase behaviour of aqueous suspensions of the fully hydrated phospholipid - 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were characterised using small angle scattering of synchrotron radiation (SAXS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The surfactant studied caused a destabilisation of the lamellar phase typical of DPPC. Addition of the surfactant also shifted to lower temperatures and extended the range of the main phase transition
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Acta Physica Polonica A, 121(4), 893-898, (2012) |
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Structure and morphology of gold nanoparticles in solution studied by TEM, SAXS and UV-VIS Gold nanoparticles have a great number of applications, among others in material sciences, biology and medicine. A method for the synthesis of gold nanoparticles in solution with the use of gemini surfactant was proposed and the nanoparticles obtained were subjected to thorough characterisation. The method proposed is a modification of the Turkevich method, based on reduction of tetrachloroauric acid in the presence of trisodium citrate and a dicationic (gemini) surfactant - 1,1'-(1,4-butan)bis(3-dodecyloxymethylimidazolium) di-propionate. Morphology and size distribution of gold nanoparticles obtained were examined by the transmission electron microscopy (TEM), UV-Vis spectroscopy and small angle scattering of synchrotron radiation (SAXS). The plasmon resonance of the nanoparticles obtained was observed in the wavelength range corresponding to the presence of gold nanoparticles with sizes ranging from 5 to 100 nm. TEM images confirmed that the spherical shape of nanoparticles was dominated in reference solutions prepared of sodium citrate and tetrachloroauric acid. In the solutions prepared with addition of gemini surfactant, the gold nanoparticles of triangular morphology were observed.
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Acta Physica Polonica A, 121(4), 888-892, (2012) |
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Koncepcja budowy linii pomiarowej MX/SAXS/XRD w NCPS SOLARIS In December 2011 the construction of the rst Polish synchrotron | The National Syn-chrotron Radiation Centre SOLARIS | was initiated in Krakow. The energy parameters of SOLARIS (1:5 GeV) allow planning of a beam line utilising the synchrotron radiation (hard X-rays range), that can be used in biocrystallography and material science. The planned beam line has three end-stations | for biocrystallography (MX), small-angle X-ray scattering (SAXS) and di raction of synchrotron radiation on polycrystalline materials (XRD).
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Synchrotron Radiation in Natural Science, 11(1-2), 5-9, (2012) |
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(Pobrane: aktualizowanie) |
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Zaktualizowano: podstrony 2021-06-21 / bazę danych: 2024-11-02 by Webmaster: Zbigniew Fojud