Adsorption of Uranyl Ions into Poly(Acrylamide‐co‐Acrylic Acid) Hydrogels Prepared by Gamma Irradiation

Acrylamide (AAm)/Acrylic Acid (AAc) copolymers have been prepared by gamma irradiation of binary mixtures at three different compositions where the acrylamide/acrylic acid mole ratios varied around 15, 20, and 30%. Threshold dose for 100% conversion of monomers into hydrogels was found to be 8.0 kGy. Poly(Acrylamide‐co‐Acrylic Acid) (poly(AAm‐co‐AAc)) hydrogels have been considered for the removal of uranyl ions from aqueous solutions. Swelling behavior of these hydrogels was determined in distilled water at different pH values and in aqueous solutions of uranyl ions. The results of swelling tests at pH 8.0 indicated that poly(AAm‐co‐AAc) hydrogel, containing 15% acrylamide showed maximum % swelling. Diffusion of water and aqueous solutions of uranyl ion into hydrogels was found to be non‐Fickian in character and their diffusion coefficients were calculated. The effect of pH, composition of hydrogel, and concentration of uranyl ions on the adsorption process were studied at room temperature. It was found that one gram of dry poly(AAm‐co‐AAc) hydrogel adsorbed 70–320 mg and 70–400 mg uranyl ions from aqueous solutions of uranyl nitrate and uranyl acetate in the initial concentration range of 50–1500 mg UO₂ ²⁺L^?, depending on the amount of AAc in the hydrogels, respectively. Adsorption isotherms were constructed for poly(AAm‐co‐AAc)–uranyl ion system indicating an S type of adsorption in the Giles classification system. It is concluded that crosslinked poly(AAm‐co‐AAc) hydrogels can be successfully used for the removal of uranyl ions from their aqueous solutions.     

Synthesis of Cyclic Poly(Methacrylic Acid) by Template Polymerization of β-Cyclodextrin Monomer

Atom transfer radical polymerization of template monomer synthesized by introduction of methacryloyl groups into secondary hydroxyl groups of -cyclodextrin [-CD] was carried out with 1,3-dibromobutane as an initiator. Then, closing of polymerized methacryloyl groups was carried out by reaction of bromine groups at both ends with 1,3-diamino propane [DAP] or 1,4-diamino butane [DAB]. The macrocyclic poly(methacrylic acid) [PMAA] obtained by hydrolysis of products was analyzed by GPC, MALDI-TOF-mass. It was found that template monomer of -CD was effective for synthesisof macrocyclic oligomers and that DAP was the preferred closing reagent for the methacryloyl groups polymerized in the template monomer.     

Effect of Physical Aging on Heterogeneity of Poly(ε-caprolactone) Toughening Poly(lactic acid) Probed by Nanomechanical Mapping

Poly(lactic acid)(PLA) is a promising bio-based environmentally-friendly plastic. Nevertheless, the physical aging-induced brittleness of PLA limits its widespread applications. Blending with immiscible ductile polymer is an effective way to toughen PLA. However, the underlying details of the toughening mechanism and, in particular, the effect of physical aging are not well understood. Herein, atomic force microscopy(AFM) based nanomechanical mapping technology was utilized to visualize the diff...     

A Highly Efficient Glycosidation of Glycosyl Chlorides by Using Cooperative Silver(I) Oxide–Triflic Acid Catalysis

Following our discovery that silver(I) oxide-promoted glycosylation with glycosyl bromides can be greatly accelerated in the presence of catalytic TMSOTf or TfOH, we report herein a new discovery that glycosyl chlorides are even more effective glycosyl donors under these reaction conditions. The developed reaction conditions work well with a variety of glycosyl chlorides. Both benzoylated and benzylated chlorides have been successfully glycosidated, and these reaction conditions proved to be effective in coupling substrates containing nitrogen and sulfur atoms. Another convenient feature of this glycosylation is that the progress of the reaction can be monitored visually; its completion can be judged by the disappearance of the characteristic dark color of Ag₂O.     

The Effect of Copolymer Composition on Surface Free‐Energy of Poly(2‐Hydroxyethyl Methacrylate–Crotonic Acid) Copolymers

Abstract

Poly(2‐hydroxyethyl methacrylate–crotonic acid) P(HEMA/CrA) copolymers with varying compositions were prepared from ternary mixtures of 2‐hydroxyethyl methacrylate (HEMA)/crotonic acid (CrA)/water by using ⁶⁰Co γ‐rays. The wetting forces were determined according to the Wilhelmy Plate Technique. Di‐iodomethane, ethylene glycol, and formamide were used as probe liquids. Lifshitz–van der Waals surface energy components, Lewis acid–base surface components, and total surface energies were calculated using van Oss et al. methodology. It was determined that Lifshitz–van der Waals component (γ_S ^LW) of the copolymers did not differ much from the copolymer composition. However, the electron‐donor surface free energy components (γ_S ^?) of the copolymers were decreased considerably with the increase of the CrA content of the copolymers, the surfaces of these copolymers were still found to have a basic character.     

Synthesis of Vinyl Polymer—Poly (α-Amino Acid) Block Copolymers by End-Reactive Oligomers

In order to synthesize block copolymers consisting of segments having dissimilar properties, vinyl polymer - poly (α-amino acid) block copolymers were synthesized by two different methods. In the first method, the terminal amino groups of polysarcosine, poly(γ-benzyl L-glutamate), and poly(γ-benzyloxycarbonyl-L-lysine) were haloacetylated. The mixture of the terminally haloacetylated poly (α-amino acid) and styrene or methyl methacrylate was photoirradiated in the presence of Mo (CO)₆ or heated with Mo(CO)₆, yielding A-B-A-type block copolymers consisting of poly(α-amino cid) (the A component) and vinyl polymer(the B component). The characterization of block copolymers revealed that the thermally initiated polymerization of vinyl compounds by the trichloroacetyl poly(α-amino acid)/Mo(CO)₆ system was most suitable for the synthesis of vinyl polymer - poly-(α-amino acid) block copolymers. In the second method, poly (methyl methacrylate) and polystyrene having a terminal amino group were synthesized by the radical polymerization in the presence of 2-mercaptoethylammonium chloride. Using these polymers having a terminal amino group as an initiator, the block polymerizations of γ-benzyl L-glutamate NCA and e-benzyloxycarbonyl-L-lysine NCA were carried out, yielding A-B-type block copolymer. By eliminating the protecting groups of the side chains of poly(α-amino acid) segment, block copolymers such as poly(methyl methacrylate) with poly(L-glutamic acid) or poly(L-lysine) and polystyrene with poly(L-glutamic acid) and poly(L-lysine) were successfully synthesized.     

IR Spectroscopic Study of Chemical Transformations upon Irradiation of the Poly(vinyl chloride)–Triallyl Cyanurate System

Chemical transformations resulting from irradiation of the poly(vinyl chloride) (PVC)–triallyl cyanurate (TAC) system were studied by IR spectroscopy. It was shown that crosslinking was accompanied by scission of the network structure formed in the initial dose range, and the scission process occurred even at small irradiation doses. The scission is assumed to be localized at the interface boundary between PVC and poly(iso-TAC) or poly(TAC).     

Thermal Effect of Phosphate Salt Additives on Poly(L‐Lactic Acid) and the Coordination Structure

Poly(L‐lactic acid) (PLLA) was mixed with a few weight percent of magnesium or calcium hydrogen phosphate to improve the thermal property. Calcium hydrogen phosphate as an additive to PLLA was found to be more effective in increasing the glass transition point (T_g) than magnesium hydrogen phosphate, which was investigated by the differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Studies on the coordination structure for the polymer complex (ca‐(plla)) confirmed by infrared (IR) spectroscopy and extended X‐ray absorption fine structure (EXAFS) indicated that calcium ion radius would be suitable for the coordination with carbonyl groups of polymer chains.     

Preparation of Poly(methyl methacrylate) Nanoparticles 15–50 nm in Diameter from Submicrometer-Sized Latex Particles

Russian Journal of Applied Chemistry - A procedure was developed for preparing poly(methyl methacrylate) nanoparticles of 15–50 nm size from coarser (200–300 nm) polymer latex particles...     

Spectroelectrochemistry of Poly(3,4-Ethylenedioxythiophene)–Tungsten Oxide Composite Films in Dilute Sulfuric Acid Solution

Russian Journal of General Chemistry - Using electrochemical deposition of tungsten oxide from a metastable acidic solution of isopolytungstates into a poly(3,4-ethylenedioxithiophene) film,...     

Enhanced Crystallization Rate of Biodegradable Poly(ε-caprolactone) by Cyanuric Acid as an Efficient Nucleating Agent

The influence of cyanuric acid(CA) as an efficient nucleating agent on the crystallization behavior and morphology of biodegradable poly(ε-caprolactone)(PCL) was extensively studied in this work with several techniques for the first time. The nonisothermal melt crystallization behavior and overall isothermal melt crystallization rate of PCL were significantly enhanced by only a small amount of CA. The addition of CA apparently improved the nonisothermal melt crystallization peak temperature, overall isothermal melt crystallization rate, and nucleation density of PCL spherulites, but did not modify the crystallization mechanism and crystal structure of PCL, indicating that CA was an efficient nucleating agent for the crystallization of PCL. The possible nucleation mechanism of CA on the crystallization of PCL was also discussed on the basis of their crystal structures.     

Thermal Degradation of Poly(ε-caprolactone), Poly(L-lactic acid) and their Blends with Poly(3-hydroxy-butyrate) Studied by TGA/FT-IR Spectroscopy

Summary: The thermal degradation behavior of poly(ε-caprolactone) (PCL) and poly(L-lactic acid) (PLA) have been studied in different environment. It was found that these polymers undergo completely different degradation processes in nitrogen and oxygen atmosphere. In oxygen environment PCL and PLA mainly decompose to CO₂, CO, water and short-chain acids. In nitrogen atmosphere PCL releases 5-hexenioc acid, CO₂, CO and ε-caprolactone, whereas PLA decomposes to acetaldehyde, CO₂, CO and lactide. The polymer blends of poly(3-hydroxybutyrate) (PHB) with PCL and PLA decompose similar to the individual homopolymers with crotonic acid as the initial decomposition product of PHB.     

Preparation of Macroporous Poly(vinyl alcohol-co-triallyl isocyanurate)Beads Bearing Aminocarboxylic Acid as Functional Groups by Suspension Polymerization

Macroporous poly(vinyl acetate-co-triallyl isocyanurate)beads were prepared with suspension polymerization method.The copolymer beads were then transformed into poly(vinyl alcohol-co-triallyl isocyanurate)by ester exchange reaction.Aminocarboxylic acids were immobilized on the copolymer beads by the esterification of hydroxyl groups with diethyl-lenetriaminepentaacetic bisanhydride,The weak acid exchange capacities,specific surface areas and mean pore diameters of the rsultant resin beads were measured.     

Effect of the Composition of Ethanol–DMSO Solvents on the Stability of Silver(I) Complexes with 18-Crown-6

The effect of composition of ethanol–dimethyl sulfoxide (EtOH–DMSO) solvents (χ_DMSO = 0.0–1.0 mole fractions) on the stability of silver(I) complexes with 18-crown-6 ether (18C6) has been studied potentiometrically at 298.15 K. The increasing of DMSO concentrations in mixed solvents are shown to considerably reduce the stability of 18C6 complexes with silver(I) ion ([Ag18C6]⁺). A change in the solvation state of the central ion is suggested to be the key factor in shifting complexing equilibrium.     

Full Protection of Intensely Luminescent Gold(I)–Silver(I) Cluster by Phosphine Ligands and Inorganic Anions

An intensely luminescent gold(I)–silver(I) cluster [(C)(AuPPhpy₂)₆Ag₆(CF₃CO₂)₃](BF₄)₅ (PPhpy₂=bis(2-pyridyl)phenylphosphine) ( 3 ) is synthesized by the reaction of [(C)(AuPPhpy₂)₆Ag₄](BF₄)₆ with AgCF₃CO₂. All eight faces of the octahedral C@Au₆ core in 3 are capped, that is, six faces are capped by silver ions and two by tetrafluoroborates. Cluster 3 is intensely luminescent in solution with a quantum yield of 92 %. Ligation of CF₃CO₂⁻ ions is vital for the construction and emission properties of 3 , as confirmed by DFT calculations. BF₄⁻ ions are involved in the protecting sphere of the metal core, as evidenced by ¹⁹F NMR data. The participation of phosphines, CF₃CO₂⁻, and BF₄⁻ ions in the protection of the emissive core and the enhancement of the rigidity of the cluster result in the high emission efficiency. This is the first example of organic ligands and inorganic anions forming a rigid protecting sphere for luminescent coinage-metal clusters.     

Double-Layered Plasmonic–Magnetic Vesicles by Self-Assembly of Janus Amphiphilic Gold–Iron(II,III) Oxide Nanoparticles

Janus nanoparticles (JNPs) offer unique features, including the precisely controlled distribution of compositions, surface charges, dipole moments, modular and combined functionalities, which enable excellent applications that are unavailable to their symmetrical counterparts. Assemblies of NPs exhibit coupled optical, electronic and magnetic properties that are different from single NPs. Herein, we report a new class of double-layered plasmonic–magnetic vesicle assembled from Janus amphiphilic Au-Fe₃O₄ NPs grafted with polymer brushes of different hydrophilicity on Au and Fe₃O₄ surfaces separately. Like liposomes, the vesicle shell is composed of two layers of Au-Fe₃O₄ NPs in opposite direction, and the orientation of Au or Fe₃O₄ in the shell can be well controlled by exploiting the amphiphilic property of the two types of polymers.     

Microwave Synthesis and Characterization of a Silver–Poly (Amide Amine) Dendrimer Nanocomposite with Application as a Hydrogen Peroxide Sensor

A novel procedure to fabricate a nonenzymatic hydrogen peroxide sensor was developed based on a silver-poly (amide amine) dendrimer nanocomposite synthesized by a microwave procedure. The formation of silver nanoparticles functionalized with the poly (amide amine) dendrimer was confirmed by ultraviolet visible spectroscopy, high resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The electroanalytical properties of a glassy carbon electrode modified with the silver-poly (amide amine) dendrimer nanocomposite were evaluated by the determination of hydrogen peroxide. The electrochemical sensor exhibited rapid response and high sensitivity to hydrogen peroxide with a linear dynamic range from 1.0 × 10–5 to 3.7 × 10–3 molar (r = 0.998) and a limit of detection of 5.06 micromolar. The sensitivity was 30.24 microampere · per millilmolar per square centimeter and the response time was three seconds at a working potential of ?0.35 volt. In addition, the sensor was unaffected by the presence of ascorbic acid, citric acid, and oxalic acid. These results indicate that the silver-poly (amide amine) dendrimer nanocomposite based sensor has application for the determination of hydrogen peroxide.