Effect of gamma radiation on the molecular-topological structure and properties of poly(vinylidene fluoride) and the matrix in a PVDF-based glass-reinforced plastic

The amorphous-topological structure of poly(vinylidene fluoride) (PVDF), the pseudo-network structure of which is formed by polyassociative entities of the cluster type and persists upon γ-irradiation up to 250 kGy, has been investigated. As a result of the processes involved in the fabrication of the glass-reinforced plastic (GRP), five crystalline modifications arise in the polymer matrix instead of cluster branching points in the initial PVDF, and the temperature of the molecular flow of the polymer matrix in the GRP rises from 410 to 593 K in comparison with the initial PVDF. The strength of GRP made of untreated glass cloth (110 MPa) is higher than that of the initial PVDF (86 MPa). However, when using glass cloth treated with a process sizing agent, the strength of the GRP increases up to 286 MPa. After γ-irradiation of the latter, upon which a sharp drop in the strength is observed immediately with the onset of GRP irradiation, the exposure of PVDF and GRP made of untreated glass cloth results in a drop in the strength only after 50 kGy. The irradiation eliminates the properties acquired by the polymer matrix during the fabrication of GRP, and the properties of the GRP polymer matrix approach those of the initial PVDF with an increase in the radiation dose.     

Segmented polyurethane elastomers derived from aliphatic polycarbonate and poly(ester‐carbonate) soft segments for biomedical applications

A series of biomedical polyurethane elastomers (PURs) based on poly(ester‐carbonate)s (PECs) and polycarbonates (PCs) were synthesized and spectrally characterized fully. PEC or PC diols were synthesized by the ring‐opening polymerization of ε‐caprolactone, trimethylene carbonate, and neopentyl carbonate catalyzed by lipase from Candida antarctica. PURs were prepared by free‐metal method from PEC or PC diols and 4,4′‐methylenebis(phenyl isocyanate), with 1,4‐butanediol as a chain extender. The physical and mechanical properties as well as hydrolytic stability of the obtained PURs were determined. The toxicity of the received polymers was evaluated using bacterial luminescence test and two protozoans assays. The presented preliminary studies suggest that PEC or PC diols prepared in this way might be applied for the synthesis of biomedical PURs with improved hydrolytic stability. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Influence of drug on the structure and segmental mobility of poly(3-hydroxybutyrate) ultrafine fibers

Ultrafine fibers of biodegradable natural polyester such as poly(3-hydroxybutyrate) containing dipyridamole at various concentrations as a drug are prepared by the electrospinning method. It is shown by scanning electron microscopy that the absence of dipyridamole or its low concentrations (from 0 to 1%) provide the complex morphology of fibers composed of cylindrical regions 1–3 μm in diameter and thickened spindle-like ones 5–7 μm in average diameter. An increase in the concentration of dipyridamole in fibers leads to disappearance of the latter regions, with the morphology being cylindrical. The features of the crystalline and amorphous structures of poly(3-hydroxybutyrate) and its mixtures with dipyridamole are examined via DSC and EPR probe techniques. It is shown that the addition of dipyridamole to the poly(3- hydroxybutyrate) polymer matrix results in a sharp increase in the crystallinity and a slowdown of the molecular mobility in amorphous regions of ultrafine fibers. The heat treatment (annealing) of fibers leads to a sharp increase in the polymer crystallinity and a reduction of the segmental mobility in intercrystalline regions of the initial poly(3-hydroxybutyrate) fibers and those containing 1% of dipyridamole. All results including the influence of the drug concentration on the shape of fibers and their dynamic characteristics agree well with the thermal and physical parameters and should be used in the design of therapeutic systems for targeted and sustained delivery of bioactive compounds.     

UPLC a Powerful Tool for the Separation of Imidazolium Ionic Liquid Cations

Ultra-performance liquid chromatography (UPLC) in reversed-phase (RP), ion pair (IP) and hydrophilic interaction chromatography (HILIC) has been investigated for the separation of imidazolium-based ionic liquid (IL) cations. Among the three stationary phases (i.e., C18, C8 and phenyl) studied under RP conditions the phenyl phase provided much stronger retention for the IL cations. Four acids (hydrochloric, methanesulfonic, perchloric and trifluoroacetic) as mobile phase additives were compared in light of their effects on the retention of IL cations. It was shown that the retention of all IL cations decreased upon acidification of the mobile phase, possibly due to suppression of residual silanol ionization. Very fast (~3 min) and efficient RP-UPLC separation of six cations was achieved by gradient elution with acetonitrile?Cwater mobile phase containing 2.5 mmol L^?1 perchloric acid. In IP-UPLC all solutes were well resolved in about 4 min by gradient elution with acetonitrile?Cwater mobile phase containing 1 mmol L^?1 sodium 1-octanesulfonate as ion pairing reagent. Finally, under HILIC conditions by using isocratic elution with acetonitrile?Cwater (85:15, v/v) mobile phase containing 5 mmol L^?1 ammonium formate (pH 3.2) the separation time was reduced to less than 2 min while maintaining excellent peak shapes and sufficient resolution. Compared to current LC systems UPLC allowed considerably faster separations with better peak shapes.     

Comparison of LC Columns Packed with 2.6?��m Core-Shell and Sub-2?��m Porous Particles for Gradient Separation of Antibiotics

The recently introduced Kinetex C18 column packed with core-shell 2.6 ??m particles is declared to provide similar efficiency and short analysis as Acquity BEH C18 column with 1.7 ??m porous particles. Unlike Acquity BEH C18 column, Kinetex C18 column exhibited lower column backpressure making this column compatible to conventional LC systems. The performance of Kinetex C18 column (2.1 × 50 mm) and Acquity BEH C18 column (2.1 × 50 mm) for gradient separation of tetracyclines under acidic conditions (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) and macrolides under alkaline conditions (tylosin, clarithromycin, roxithromycin, and carbomycin) was studied. The columns were compared by evaluation of their experimental peak capacity and its dependence on linear velocity and gradient slope. The maximal experimental peak capacities for analysis of tetracyclines were 51.8 (Acquity BEH C18 column) and 48.4 (Kinetex C18 column). This indicated that Kinetex C18 was a suitable alternative to Acquity BEH C18 column for the analysis of tetracyclines under acidic conditions. On the contrary, the maximal experimental peak capacities for analysis of macrolides on Acquity BEH C18 column was higher (46.7) than that on Kinetex C18 column (36.9). Moreover, application of Kinetex C18 column for the analysis of macrolides under alkaline conditions was limited with respect to its decreasing performance with growing number of injections on the column.     

Expedient Access to Functionalized Furan/3(2H)-furanone Ensembles via Microwave-Assisted Domino Reactions

A one-pot linkage between furan and 3(2H)-furanone rings has been effected via the microwave-assisted Et₃N-catalyzed domino condensation of the furan and benzofuran carboxylic acids with available cyanopropargylic alcohols (MeCN, 100 °C, 1.2 atm, 2–17 h). Despite involving a number of C-H-forming/breaking steps, the assembly is chemoselective and the final products, 5-(2-furyl)-3(2H)-furanones, are formed in 59–96% yields.     

Acceleration complex for extreme ultraviolet nanolithography based on a free-electron laser with kilowatt-scale average radiation power

The project of an acceleration complex is described that is based on a 0.7-GeV superconducting linear accelerator for the free-electron laser used for extreme ultraviolet lithography at a 13.5-nm wavelength with a 0.5-kW average power of laser radiation, as well as for examination of materials using X-ray and vacuum-ultraviolet radiations.     

Optical,nanostructural, and biophysical properties of Zn-induced changes in human erythrocyte membranes

We studied changes in the surface of erythrocyte membranes exposed to the action of zinc sulfate in the concentration range of 0.1–2.0 mM/l using methods of light scattering, spectrofluorimetry, and atomic force microscopy. Using the spectrofluorimetry method, we revealed a dose-dependent increase in the fluorescence intensity of a fluorescamine probe incorporated into erythrocyte membranes modified by zinc ions, which is indicative of an increase in the level of NH₂ groups on the cell surface. Using atomic force microscopy, we revealed changes in the surface topography of erythrocyte membranes exposed to the action of zinc sulfate in the concentration range of 0.1–2.0 mM/l. By performing a correlation analysis, we revealed that the correlation length of the autocorrelation function of the erythrocyte surface irregularity profile directly related to the fluorescence intensity of fluorescamine incorporated into erythrocyte membranes (r = 0.9, p < 0.05) modified by zinc ions. We showed that, in the zinc sulfate concentration range of 0.1–2.0 mM/l, zinc oxides form in erythrocyte membranes, which is confirmed by the appearance of an absorption band at 330–340 nm and by an increase in the light scattering. At more considerable concentrations, we identified absorption bands characteristic of zinc protein complexes in erythrocyte membranes. A considerable decrease in the elongation of the scattering indicatrix of erythrocyte membranes caused by luminescence correlates with the content of zinc proteins. Polarization measurements confirm the enhancement of the aggregation of protein complexes observed by the atomic force microscopy method. The proposed complex approach can be used in studies on the action of various abiotic factors on biological cells.     

IR reflectance spectra and optical constants of Al-Cu-Fe quasicrystalline thin films

The optical properties of Al-Cu-Fe quasicrystalline films and, for comparison, crystalline films of similar composition are studied using middle-and far-IR reflectance spectroscopy. Measurements are performed with 0.1-to 0.3-μm-thick films on sapphire substrates. The complex dielectric function of the films is calculated from experimental data. It is found that the real part of the dielectric function is negative for the crystalline films but positive and weakly frequency dependent, except in the range near 245 cm^?1, for the quasicrystalline films. The optical conductivity of the quasicrystalline films does not feature the Drude peak observed for crystalline films and exhibits a peak at 245 cm^?1, which can be assigned to optical phonon excitations and is absent for crystalline films.