Thermal degradation and pyrolysis study of phosphorus‐containing polysulfones

This article deals with the thermal decomposition behavior of a polysulfone containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide versus the initial chloromethylated polysulfone under an inert atmosphere and in air. Thermogravimetric characteristics from thermogravimetry and differential thermogravimetry data revealed important differences related to the employed atmosphere, the types of substituted functional groups, or the degree of substitution. The introduction of the 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide pendent group into polysulfone enhanced the thermal stability of the initial chloromethylated polysulfone in both an inert atmosphere and air. Thermal degradation in nitrogen consisted of one degradation step, whereas thermooxidative degradation in air involved more steps. In air, the degradation mechanism was more complex. The volatile products and solid residues that resulted after pyrolysis in an inert atmosphere and in air were analyzed with Fourier transform infrared and mass spectrometry. Environmental scanning electron microscopy showed that the char residues had different morphologies, which suggested that a more compact structure led to better resistance to heat and oxygen. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2011     

Crosslinked polysulfone obtained by Wittig‐Horner reaction in biphase system

Phase transfer catalyzed reactions are often more easily and cheaply performed than conventional method and they are therefore of particular interest. A polysulfone functionalized with phosphonate (2‐PSF) was prepared under phase transfer catalysis (PTC) conditions, and it was evaluated by spectrometric method (Fourier transform infrared spectroscopy, using potassium bromide (KBr) pellet). The phosphorus content of the modified polysulfone was determined, and it was used for the determination the fraction of repeating units functionalized with phosphonate groups. The modified polysulfone contains 1.40 mmol phosphonate/g polysulfone. Polysulfone functionalized with phosphonate groups and polysulfone functionalized with aldehyde groups (3‐PSF) were used in Wittig‐Horner reaction, to introduce double bonds on polymer and to obtain crosslinked polysulfone (4‐PSF). The reactions were performed using PTC method, solid‐liquid (potassium carbonate (K₂CO₃), tetrahydrofuran (THF), tetraethylammonium iodide (TEAI)) system. The structure of polysulfone functionalized with phosphonate groups and polysulfone functionalized with aldehyde group were confirmed by ¹H‐, ¹³C‐, and ³¹P‐nuclear magnetic resonance (NMR). The peak for phosphorus in PSF‐phosphonate appears in ³¹P NMR spectrum as a singlet at 25.712 ppm. The thermal properties of aldehyde, phosphonate, and crosslinked polysulfone were studied by thermogravimetric analysis (TG) and differential thermogravimetric analysis (DTG). Scanning electron microscopy images for polysulfone functionalized with phosphonate and crosslinked polysulfone are in concordance with nitrogen (N₂) adsorption‐desorption isotherms.POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Magnetite nanoparticles for functionalized textile dressing to prevent fungal biofilms development

ABSTRACT: The purpose of this work was to investigate the potential of functionalized magnetite nanoparticles to improve the antibiofilm properties of textile dressing, tested in vitro against monospecific Candida albicans biofilms. Functionalized magnetite (Fe3O4/C18), with an average size not exceeding 20 nm, has been synthesized by precipitation of ferric and ferrous salts in aqueous solution of oleic acid (C18) and NaOH. Transmission electron microscopy, X-ray diffraction analysis, and differential thermal analysis coupled with thermo gravimetric analysis were used as characterization methods for the synthesized Fe3O4/C18. Scanning electron microscopy was used to study the architecture of the fungal biofilm developed on the functionalized textile dressing samples and culture-based methods for the quantitative assay of the biofilm-embedded yeast cells. The optimized textile dressing samples proved to be more resistant to C. albicans colonization, as compared to the uncoated ones; these functionalized surfaces-based approaches are very useful in the prevention of wound microbial contamination and subsequent biofilm development on viable tissues or implanted devices.     

Improvement of the corrosion resistance and structural and mechanical properties of a titanium base alloy by thermo‐mechanical processing

In this work, a new ternary Ti–25Ta–5Zr alloy (with nontoxic alloying elements) was obtained and used to develop a thermo‐mechanical procedure in order to optimize the balance strength – elastic modulus. Data about structural (by SEM) and mechanical properties are investigated. Also, its electrochemical behaviour in Ringer–Brown and Ringer solutions of different pH values (simulating severe functional conditions of an implant) was studied by cyclic potentiodynamic and linear polarization and electrochemical impedance spectroscopy (EIS). From cyclic potentiodynamic polarization curves it resulted the nobler behaviour of the thermo‐mechanical treated alloy than as‐cast alloy due to the favourable influence of the applied processing. Impedance spectra were fitted with one time constant equivalent circuit characterizing a very stable, resistant oxide passive film. The values of the open circuit potentials for the treated alloy are nobler than of the as‐cast alloy and tended to more positive values in time, proving that the passive film on its surface is more compact and thickened in time.     

Synthesis and characterization of phosphorus‐containing polystyrene

Poly(o‐toluidine) ( POT) has been electrodeposited on brass from an aqueous salicylate solution by using cyclic voltammetry, and its corrosion protection performance has been evaluated by potentiodynamic polarization technique and electrochemical impedance spectroscopy in aqueous 3% NaCl solution. The corrosion potential was about 0.115 V vs. SCE more positive for the POT‐coated brass than that of uncoated brass and reduces the corrosion rate of brass almost by a factor of 800. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterisation of anodic films formed on titanium and its alloys

The properties of the anodic oxide films formed on titanium and its implant alloys Ti‐5Al‐4V and Ti‐6Al‐4Fe are investigated in this paper. Anodic oxide films were prepared by electrochemical treatment in 3M sulphuric acid solution at 60 V for 1 min, followed by a thermal treatment consisting of heating at 500°C for 24 h and then cooling in water. Electrochemical impedance spectroscopy (EIS) measurements were carried out at open circuit potential. Nyquist and Bode spectra exhibit a two‐time constant system, attesting an oxide with two layers: a barrier inner oxide and a porous outer one. All spectra change in time, indicating a thickening of the films. Open circuit potentials were monitored (long‐term, 25,000 exposure hours) in Ringer 2 solution of different pH values (6.98, 4.35, 2.5) for titanium, Ti5Al‐4V and Ti‐6Al‐4Fe alloy but without treatment with the purpose to compare the biomaterial behaviour. It was pointed out some variations of the open circuit potentials around electropositive values, suggesting slow dissolution, re‐passivation or adsorption processes.     

Sorption of organic compounds on strong basic macroporous anion exchangers

The behavior of various strong basic type II macroporous anion exchangers against the sorption of some organic acid alkaline salts as follows: natrium benzoate, natrium benzenesulfonate, potassium α-naphthylacetate, natrium β-naphthalenesulfonate, and natrium anthraquinone-2-sulfonate was established. The values of the sorption capacities depend on the morphology of anion exchanger network, the type and the size of organic anion, as well as the type of anion exchanger.     

Intracellular Delivery of Doxorubicin by Iron Oxide-Based Nano-Constructs Increases Clonogenic Inactivation of Ionizing Radiation in HeLa Cells

In this study, we determined the potential of polyethylene glycol-encapsulated iron oxide nanoparticles (IONP_CO) for the intracellular delivery of the chemotherapeutic doxorubicin (IONP_DOX) to enhance the cytotoxic effects of ionizing radiation. The biological effects of IONP and X-ray irradiation (50 kV and 6 MV) were determined in HeLa cells using the colony formation assay (CFA) and detection of γH2AX foci. Data are presented as mean ± SEM. IONP were efficiently internalized by HeLa cells. IONP_CO radiomodulating effect was dependent on nanoparticle concentration and photon energy. IONP_CO did not radiosensitize HeLa cells with 6 MV X-rays, yet moderately enhanced cellular radiosensitivity to 50 kV X-rays (DMF_SF0.1 = 1.13 ± 0.05 (p = 0.01)). IONP_DOX did enhance the cytotoxicity of 6 MV X-rays (DMF_SF0.1 = 1.3 ± 0.1; p = 0.0005). IONP treatment significantly increased γH2AX foci induction without irradiation. Treatment of HeLa cells with IONP_CO resulted in a radiosensitizing effect for low-energy X-rays, while exposure to IONP_DOX induced radiosensitization compared to IONP_CO in cells irradiated with 6 MV X-rays. The effect did not correlate with the induction of γH2AX foci. Given these results, IONP are promising candidates for the controlled delivery of DOX to enhance the cytotoxic effects of ionizing radiation.