One-Pot Synthesis of Cyclomatrix-Type Polyphosphazene Microspheres and Their High Thermal Stability.

Highly cross-linked inorganic and organic hybrid cyclomatrix-polyphosphazenes microspheres (C-PPZs) have been successfully synthesized by a one-pot polymerization technique between hexachlorocyclotriphosphazene and p-phenylenediamine in the presence of triethylamine (TEA), and they were used for enhancing the flame retardancy of epoxy resins (EPs). A thermoset EP was prepared by incorporating different percentages (2, 5, and 10%) of C-PPZs into diglycidyl ether of bisphenol A (DGEBA). The results reveal that the size and morphology of the microspheres can be tuned by varying the synthesis temperature. The average size of C-CPPZs gradually increased from 3.1, 4.9, to 7.8 µm as the temperature was increased from 100, 120, to 200 °C, respectively. The thermogravimetric analysis showed that the C-CPPZ microspheres have good thermal stability up to 900 °C with about ∼10 wt % mass loss for C-CPPZs formed at 200 °C compared to ∼30 wt % mass loss for those obtained at 100 and 120 °C. The 10% loss at 900 °C is much lower than the previous research concerning the thermal stability of cyclophosphazene, in which more weight losses were observed at lower temperatures. The resulting C-CPPZ microspheres were characterized by spectroscopic and imaging techniques including Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, and X-ray photoelectron spectroscopy.

Hexachlorocyclotriphosphazene Functionalized Graphene Oxide as a Highly Efficient Flame Retardant.

A flame-retardant composite was synthesized through a simple graphene oxide functionalization route with hexachlorocyclotriphosphazene and p-phenylenediamine. Flame experiments conducted on the synthesized composite proved its importance as tremendously resistant to fire. The thermogravimetric analysis (TGA) shows clearly that the functionalized graphene oxide (FGO) exhibits an enhanced thermal stability and better temperature resistance. A thermoset epoxy resin was prepared by incorporating different percentages (2, 5, and 10%) of FGO to diglycidyl ether of bisphenol A (DGEBA). The flame-retardant properties, thermal degradation behavior, and combustion of the DGEBA thermosets cured by m-phenylenediamine were investigated using a Bunsen burner flame approaching the flame temperature of a fire and TGA. The chemical structure of FGO was characterized with spectroscopic and imaging techniques including Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, TGA, scanning electron microscopy, energy-dispersive X-ray spectroscopy elemental mapping, and X-ray photoelectron spectroscopy. Due to its high flame-retardant capabilities, such a composite could promise potential applications in the manufacture of inflammable materials for different uses.

Graphene Oxide Membrane Immobilized Aptamer as a Highly Selective Hormone Removal.

Three-dimensional (3D) reduced graphene oxide (rGO) modified by polyethyleneimine (PEI) was prepared and functionalized by fluorophore-labeled dexamethasone-aptamer (Flu-DEX-apt) via π-π stacking interaction. The rGO/PEI/Flu-DEX-apt was used as a selective membrane for dexamethasone hormone removal from water. The prepared rGO/PEI/Flu-DEX-apt membranes were stable, insoluble, and easily removable from liquid media. The membrane was characterized by Raman spectroscopy, scanning electron spectroscopy, and FTIR spectroscopy. The rGO/PEI/Flu-DEX-apt membrane showed high sensitivity and specificity toward the dexamethasone hormone in the presence of other steroid hormone analogs, such as progesterone, estrone, estradiol, and 19-norethindrone. The fluorescence and UV-visible spectroscopy were used to confirm the membranes performance and the quantification of hormones removal. The resulting data clearly show that the graphene oxide concentration influence the aptamers and analytes interaction (π-π stacking interaction). It was found that by varying the graphene oxide concentration yields to different porosities of rGO/PEI/Flu-DEX-apt membranes affects the adsorption recovery rate, as well as the specificity and selectivity toward the dexamethasone hormone.