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Water-Soluble Polyglycidol-Grafted Ladder Calix Resorcinarene Oligomers with Open Chain and Cyclic Topologies: Synthesis, Characteristics, and Biological Evaluation
Ladder oligomers containing calixarene skeletons in the main chain—calix[4]resorcinarene (CRA) ladder macromolecules with open chain and cyclic macromolecules with double ring-like (Noria-type) topologies—bring particular research attention as functional materials with various applications. However, there is still a remarkable lack of studies into the synthesis of fully water-soluble derivatives of these interesting macromolecules. Research on this topic would allow their bio-based research and application niche to be at least revealed. In the present study, a strategy for the synthesis of water-soluble polyglycidol-derivatized calix resorcinarene ladder oligomers with open chain and cyclic structures is introduced. A grafting from approach was used to build branched or linear polyglycidol chains from the ladder scaffolds. The novel structures were synthesized in quantitative yields and fully characterized by NMR, FTIR and UV–vis spectroscopy, gel permeation chromatography, MALDI-TOF mass spectrometry, analytical ultracentrifugation, and static light scattering to obtain the molar mass characteristics and composition. The biocompatibility and toxicity of the two polyglycidol-derivatized oligomers were investigated and the concentration dependence of the survival of three cell lines of human origin determined. The selective apoptosis effect at relatively low dissolve concentrations toward two kinds of cancerous cell lines was found.
Nanocomposite Perfluorosulfonic Acid/Montmorillonite-Na+ Polymer Membrane as Gel Electrolyte in Hybrid Supercapacitors
Solid-state supercapacitors with gel electrolytes have emerged as a promising field for various energy storage applications, including electronic devices, electric vehicles, and mobile phones. In this study, nanocomposite gel membranes were fabricated using the solution casting method with perfluorosulfonic acid (PFSA) ionomer dispersion, both with and without the incorporation of 10 wt.% montmorillonite (MMT). MMT, a natural clay known for its high surface area and layered structure, is expected to enhance the properties of supercapacitor systems. Manganese oxide, selected for its pseudocapacitive behavior in a neutral electrolyte, was synthesized via direct coprecipitation. The materials underwent structural and morphological characterization. For electrochemical evaluation, a two-electrode Swagelok cell was employed, featuring a carbon xerogel negative electrode, a manganese dioxide positive electrode, and a PFSA polymer membrane serving as both the electrolyte and separator. The membrane was immersed in a 1 M Na2SO4 solution before testing. A comprehensive electrochemical analysis of the hybrid cells was conducted and compared with a symmetric carbon/carbon supercapacitor. Cyclic voltammetric curves were recorded, and galvanostatic charge–discharge tests were conducted at various temperatures (20, 40, 60 °C). The hybrid cell with the PFSA/MMT 10 wt.% exhibited the highest specific capacitance and maintained its hybrid profile after prolonged cycling at elevated temperatures, highlighting the potential of the newly developed membrane.
ИзтеглиPreparation and antimicrobial activity of silver nanoparticles impregnated with halloysite clay
In the present work, nanotubular halloysite clay was ultrasonically treated and impregnated with silver nanoparticles. The citrate surface-stabilized silver nanoparticles dispersion was prepared using an effective method of electrochemical synthesis. The elemental and phase composition, and the structure of the obtained AgNPs-impregnated and pristine halloysite were investigated by various methods such as X-ray fluorescence (XRF), powder X-ray diffraction analyses and Fourier-transform infrared spectroscopy. The Ag-loaded halloysite sample with 0.454 wt.% silver content was confirmed by the XRF analysis. The antimicrobial activity of the pristine and the AgNPs-impregnated halloysite clay was tested against Escherichia coli ATCC 25922 (Gram-negative) and Bacillus subtilis ATCC 6633 (Gram-positive) strains. The results show that pure halloysite does not exhibit antibacterial activity. The AgNPs-impregnated halloysite demonstrates antibacterial activity against Escherichia coli and Bacillus subtilis with only bacteriostatic effect.
Formic acid electrospun composite fibers based on polyhydroxybutyrate/polyamide 6 loaded with protonated montmorillonite as promising disposable heavy metal removal sorbent
The use of electrospinable biodegradable polyhydroxyalkanoate derived from microbial sources and their combination with naturally abundant layered aluminosilicates meet the requirements for the development of new sustainable and biodegradable heavy metal ions removal fibrous sorbent materials. In the present study, novel formic acid electrospun composite biodegradable polymeric fibers based on poly β-hydroxybutyrate/polyamide 6 (PHB/PA6), loaded with protonated montmorillonite (MMT-H) at 10 and 20 wt.% were prepared for the first time by electrospinning technique. The morphology, structure and thermal stability of electrospun composite fibers were investigated by SEM, ATR FT-IR, TGA and WAXD analysis. The as obtained composite fibrous mats were evaluated for their sorption capacity towards Cu2+ and Pb2+ heavy metal ions in aqueous solution through inductively coupled plasma (ICP) analytical technique. The finding of the optimum fibers showed effective removal of both metals. However the adsorption of Pb ions is higher than Cu cations. The maximum adsorption capacities (Qmax) were 17.30 and 55.55 mg/g for Cu and Pb ions, respectively, after 60 min. The adsorption of Pb (II) ions was described by Langmuir model whereas the adsorption of Cu ions was more fitted with Freundlich model.
Corrosion Mechanism and Electrochemical Reactions on Alloy 690 in Simulated Primary Coolant of Water–Water Energy Reactors
During the power operation of the primary loop of a water cooled–water moderated energy reactor (WWER), the water chemistry evolves from a high-boron high-potassium composition to significantly lower concentrations of both constituents at the end of a campaign, and the Li concentration reaches ca. 0.7–0.9 ppm. In the present paper, the effect of primary water chemistry evolution during operation on the corrosion rate and conduction mechanism of oxides on Alloy 690 is studied by in situ impedance spectroscopy at 300 °C/9 MPa during 1-week exposures in an autoclave connected to a re-circulation loop. At the end of exposure, the samples were anodically polarized at potentials −0.8 to −0.1 V vs. SHE to evaluate the stability of the passive oxide. Simultaneously exposed samples of Alloy 690 were subsequently analyzed by XPS to estimate the thickness and in-depth composition of oxides. Impedance data were quantitatively interpreted using the mixed-conduction model (MCM) for oxide films. The effect of water chemistry evolution on the corrosion rate and conduction mechanism in the oxide on Alloy 690 in a primary coolant is discussed based on the obtained parameters.