Thermal Desorption of Covalently Bound Fullerene C60 from Poly-N-vinylpyrrolidone Films

Kinetics of formation of thermolysis products in heating of thin films of poly-N-vinylpyrrolidone and of poly-N-vinylpyrrolidone with covalently bound fullerene C₆₀ was studied by thermal desorption mass spectrometry.     

Dipole Structure and Electrooptical Properties of Poly-N-vinylpyrrolydone in Nonaqueous Solvents

Electrooptical Kerr effect and dielectric polarization were studied for poly-N-vinylpyrrolidone solutions in chloroform and in mixed chloroform-CCl₄ solvent. The results were compared with those for an analogue of the monomeric unit of poly-N-vinylpyrrolidone, low-molecular-weight compound N-methylpyrrolidone.     

Controlled radical polymerization of N-vinylpyrrolidone and N-vinylsuccinimide under the conditions of reversible chain transfer by the addition-fragmentation mechanism

Regular trends in controlled radical polymerization of N-vinylpyrrolidone and N-vinylsuccinimide by the mechanism of reversible chain transfer in the presence of a series of dithiobenzoates and trithiocarbonates were studied. The possibility of preparing soluble poly-N-vinylsuccinimide in concentrated solutions using benzyl benzodithioate as reversible chain-transfer agent was demonstrated.     

Complexation in Water-Soluble Systems Poly-N-vinylpyrrolidone-Fullerene C60

Complexes of fullerene C_{6 0} with poly-N-vinylpyrrolidone were prepared by various procedures in the presence of additional agents in solution (systems C_{6 0}-poly-N-vinylpyrrolidone and ternary system C_{6 0}-tetraphenylporphyrin-poly-N-vinylpyrrolidone) and in the solid phase (C_{6 0}-polyvinylpyrrolidone and C_{6 0}-KBr-poly-N-vinylpyrrolidone). Formation of a donor-acceptor bond in the system C_{6 0}-poly-N-vinylpyrrolidone was studied by ¹³C NMR. The conditions under which the ternary complex C_{6 0}-tetraphenylporphyrin-poly-N-vinylpyrrolidone with fullerene content varied from 1 to 5 wt % can be obtained were found.     

Effective systems based on hydrophilic polymers for extraction of phenols from aqueous solutions

Water-soluble polymers (poly-N-vinylpyrrolidone, poly-N-vinylcaprolactam, polyethylene glycol) were used for the first time for extraction of phenols from aqueous solutions. The influence exerted by pH of the aqueous solution and kind of the polymer on the degree of recovery of phenol and some of its methyl and nitro derivatives was elucidated. The correlation between the structure and extraction characteristics of phenols was interpreted.     

Interaction of copper nanoparticles with liposomes

The reduction of copper(II) ions in an aqueous dispersion of positively charged liposomes results in the formation of stable sols of a complex of copper nanoparticles with the surface of liposomes. The mean size (7 nm) and the narrow size distribution of metal nanoparticles are similar to those observed in the case of metal sol formation in polymer solutions. The labile character of bonds between nanoparticles and liposomes makes the latter able to compete with a linear polymer (poly-N-vinylpyrrolidone) in binding to nanoparticles. This ability is manifested in the independence of an almost even distribution of nanoparticles between these competitors from the sol preparation mode in a system including both poly(N-vinylpyrrolidone) macromolecules and liposomes. The evenness of the distribution indicates an approximately identical stability of complexes of copper nanoparticles with both competitors. The replacement of liposomes with poly(N-vinylpyrrolidone) macromolecules in the protective shields of nanoparticles is accompanied by the detachment of the nanoparticles from the surface, thereby allowing the measurement of their size and size distribution in the case where such measurements are impossible because of a high density of nanoparticles on the liposome surface.     

Synthesis of some azacrown derivatives and fabrication of their nanofilms on the glassy carbon surface

The modification of N-phenyl-aza-15-crown-5 (PA15C5) and N-(4-aminophenyl)-aza-15-crown-5 (4APA15C5) on glassy carbon (GC) electrode was performed by the electrochemical oxidation of the corresponding azacrown derivatives in anhydrous acetonitrile media. The electrochemical behavior of the resulting modified GC electrode was investigated in the presence of electroactive redox probes and these results, together with the X-ray photoelectron spectroscopy (XPS) and reflection-absorption infrared spectroscopy were used to confirm the attachment of these molecules onto the GC surface. The ellipsometric thicknesses of PA15C5 and 4APA15C5 films at the GC surface was obtained around 9.28 ± 0.40 and 10.50 ± 1.10 nm, respectively. Azacrown modified nanoscale surfaces serve as alkali metal sensor specific for their cavity in the crown ring.     

Preparation and Properties of Blends of Ion-Containing Polyurethane with Polyvinylpyrrolidone

Binary blends of linear polymers, segmented polyurethane [derived from oligooxytetramethylene glycol (MW 1000), toluene diisocyanate (65 : 35 isomer mixture), and magnesium p-hydroxybenzoate] and poly-N-vinylpyrrolidone (MW 10000), were prepared and studied.     

Postradiation copolymerization of N-vinylpyrrolidone with triethylene glycol dimethacrylate

The kinetics of low-temperature postradiation copolymerization of N-vinylpyrrolidone (N-VP) with triethylene glycol dimethacrylate (TGM-3) were studied using reactant mixtures with different compositions and different pre-irradiation doses, and the characteristics of the obtained copolymers were determined. The copolymerization process is most effective in glassy systems (at an N-VP concentration in solution below 80 mol %). It was shown that a poly-N-vinylpyrrolidone homopolymer is formed along with a crosslinked N-VP-TGM-3 copolymer.     

Calorimetric Properties of Different Kinds of Polymers Containing C60 Fullerene

Transformations of polymers containing C60 fullerene: poly-N-vinylpyrrolidone with the complex and covalent-graft structure, polyphenylene oxide with the complex structure, and polyethylene glycol and polystyrene with beam structure, were studied by differential scanning microcalorimetry. The observed effects were assigned to the change in nanofragmentary topology on heating.     

Extraction and preconcentration of anthocyan dye from aqueous solutions with water-soluble poly-N-vinylamides

Extraction of an anthocyan dye with poly-N-vinylpyrrolidone (PVP) and poly-N-vinylcaprolactam (PVC) under the conditions of separation of aqueous solutions of this polymer into two phases in the presence of salting-out agents (sodium chloride and sodium or ammonium sulfate) was studied.     

Polymer-analogous transformations of poly(N-vinylpyrrolidone) to produce new complexing macromolecular systems

A new polymer-analogous transformations of poly(N-vinylpyrrolidone) was used to prepare new complex-forming macromolecular systems containing thiourea and thio-semicarbazone sites. Two variants of modification were realized, namely, the method including the preliminary in situ activation of nucleophilic centres of the polymer amide fragments with dimethyl sulfate followed by introducing nucleophilic agents into the system, and the method including partial hydrolysis of poly(N-vinylpyrrolidone) followed by the amide coupling. The obtained modified polymeric materials react with silver ions in aqueous solution.     

Grafting of poly-<Emphasis Type="Italic">N</Emphasis>-methacryloylaminodeoxyglucose on poly-<Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone

A graft copolymer simulating glycoprotein was prepared by reaction of poly-N-methacryloylaminodeoxyglucose containing terminal amino group with a copolymer of N-vinylpyrrolidone and acrylic acid N-hydroxysuccinimide ester.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1356–1359.Original Russian Text Copyright © 2004 by Nazarova, Pavlov, Kever, Afanaseva, Panarin.     

Peculiarities of N-vinylpyrrolidone copolymerization with vinyl acetate in the presence of tributylborane and 1,4-benzoquinone

Copolymerization of N-vinylpyrrolidone with vinyl acetate in the presence of tributylborane and 1,4-benzoquinone has been investigated. The curves of copolymer composition and relative reactivity of monomers were obtained. An introduction of tributylborane in the monomer mixture leads to the formation of complex with N-vinylpyrrolidone. Molecular weight of the copolymers and the rate of the copolymerization decreases with the addition of tributylborane and 1,4-benzoquinone compare to conventional copolymerization initiated by dicyclohexyl peroxydicarbonate. The curve of the copolymer composition acquires an S-shape. Triad composition of the copolymers differs from the theoretical values. The reason for the observed pheno mena is realization of the effect of preferential solvation (bootstrap-effect).

     

Competition between polyelectrolyte macromolecules and amphiphilic polymer micelles in interaction with copper nanoparticles

Competition between poly(1,2-dimethyl-5-vinylpyridinium methyl sulfate) polycationic macromolecules and micelles of amphiphilic polymers containing hydrophilic and hydrophobic blocks (polyethylene glycol-600 monolaurate and poly-N-vinylpyrrolidone monostearate) for copper nanoparticles was studied by means of electrophoresis and electron microscopy techniques. It was shown that, irrespective of the formation method, almost all copper nanoparticles were bonded to the polycation in polycation-polyethylene glycol-600 monolaurate mixed solutions but were distributed between the polymers in polycation-poly-N-vinylpyrrolidone monostearate mixtures. It was concluded that the stability of the complex of copper nanoparticles with the polycation is higher than that with polyethylene glycol-600 monolaurate and is comparable with that of the copper particle-poly-N-vinylpyrrolidone monostearate complex.     

Determination of caesium-137 in water samples using modified carbon microfibers

In this paper, the possibility of caesium sorption on microfibres produced by the Slovak Academy of Sciences was investigated. Sorption capacity limit of sorbent was increased by chemical modification. The binding of Cs to the surface of potassium copper ferrocyanide modified carbon microfibers was demonstrated by SEM–EDX analysis. Statistical comparison of the models showed that the Freundlich isothermal model was more suitable for describing sorption processes. The influence of desorption, pH value, competing ions and water volume were also tested. According to the results, this method seems to be suitable for large-scale caesium separation from contaminated waters.

     

<Superscript>1</Superscript>H NMR spectra of water contained in solutions of poly(<Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone) and its modification products in CDCl<Subscript>3</Subscript>

¹H NMR spectra in CDCl₃ of poly(N-vinylpyrrolidone), epoxidized poly(N-vinyl-pyrrolidone), and products derived from the latter by modification with amino acids (glycine, β-alanine, γ-aminobutyric acid, and ε-aminocaproic acid) were examined. The ¹H NMR spectra of the modified polymers contain signals for water protons due to different centers of water sorption. These signals differ in chemical shift and integral intensity and indicate a changed spatial packing of the polymer as the result of its modification. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2377–2380, October, 2005.     

Low Temperature Catalytic Hydrolysis of Carbon Disulfide on Activated Carbon Fibers Modified by Non-thermal Plasma

In order to improve the carbon disulfide (CS₂) catalytic hydrolysis efficiency of activated carbon fibers (ACFs), ACFs surface was modified by non-thermal plasma (NTP). In particular, the effects of modification conditions on the catalyst properties were studied, including the reactor structure, modification atmosphere, modification time, output voltage and discharge gap. The catalytic activity study showed that ACFs with NTP modification enhanced CS₂ catalytic hydrolysis. The optimal reactor structure, modification atmosphere, modification time, output voltage and discharge gap was a coaxial cylinder, an N₂ atmosphere, 5 min, 7 kV and 7.5 mm, respectively. The effect of the NTP modification on the micro-structural properties of the ACFs was characterized using scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS) methods. The results showed that NTP modification improved the dispersion of functional groups and increased the number of oxygen-containing and nitrogen-containing functional groups, thus the catalytic activity could be enhanced. The present results indicated that NTP modification was an effective way to manipulate ACFs surface properties for the CS₂ catalytic hydrolysis reaction.     

Sorption of cadmium ions from aqueous solutions onto nanoporous modified carbon sorbents

Physicochemical properties of nanoporous modified carbon sorbents and sorption of cadmium ions (0.1–20 mg L^?1) onto them from nitrate solutions at pH 5–7 were studied. The acid-base nature of functional oxygen-containing groups on the carbon surface of the sorbents was determined. The ability to sorb cadmium ions depends on the kind of chemical modification of the sorbent surface.     

Modification of Poly‐ and Oligosaccharides with Os(VI)pyridine. Voltammetry of the Os(VI) Adducts Obtained by Ligand Exchange

Polysaccharides and oligosaccharides were modified with Os(VI)pyridine complex followed by ligand exchange with different ligands such as 2,2′‐bipyridine or N,N,N′,N′‐tetramethylethylenediamine. The time of the modification was much shorter (taking about 15 min) then direct modification with the given Os(VI) complex. The resulting saccharide adducts were analyzed by voltammetric methods at carbon and mercury electrodes. The results showed that the proposed technique gives promise for a new approach to analysis of glycoproteins.