Preparation of Porous Polymer Networks of <Emphasis Type="Italic">N</Emphasis>-Vinylpyrrolidone with Triethylene Glycol Dimethacrylate and Determination of Their Specific Surface Area Using Rose Bengal Dye

Porous polymer networks of N-vinylpyrrolidone with triethylene glycol dimethacrylate were prepared by three-dimensional radical copolymerization using template approach based on incorporation of macromolecular nanoobjects with porogen function. The adsorption of Rose Bengal dye from aqueous solutions onto the copolymers prepared and its desorption were studied by electronic absorption spectroscopy. The specific surface area of the porous polymer networks was estimated from the Rose Bengal adsorption data. The porous polymer networks adsorb riboflavin from aqueous solution. The riboflavin desorption is characterized by complex pattern due to washout from pores of different size.     

Structure and Properties of Networks Based on <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone and Triethylene Glycol Dimethacrylate

Using the radical copolymerization in bulk, the networks of N-vinylpyrrolidone and triethylene glycol dimethacrylate are obtained from the monomer mixture (80: 20, wt %) in the absence and in the presence of a branched copolymer consisting of the same monomer units as a template agent with the porogen function (20 wt %). It is found that the kinetics of N-vinylpyrrolidone and triethylene glycol copolymerization in the presence and in the absence of the polymer additive follows the bimodal pattern related to the copolymerization of monomers with strongly different reactivities and the homopolymerization of a less active monomer (VP) occurring in the structured densely crosslinked polymer matrix. It is shown that soluble components are extracted from the polymer networks using isopropyl alcohol and chloroform; the composition of gels and sols during the copolymerization is studied. The thermal and diffusion-sorption properties of the polymer networks obtained in the absence and in the presence of the polymer additive are investigated. The results of the diffusion-sorption probing of the polymer networks by water vapor after extraction of the polymer additive indicate the presence of pores in them. It is shown that the low-temperature adsorption of nitrogen is inapplicable to estimation of the surface characteristics of the polymer networks.     

Influence of the Molecular Mass of Poly(<Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone) on Formation of Cu<Subscript>2</Subscript>O Nanoparticles During Reduction of Divalent Copper Ions with <Emphasis Type="Italic">tert</Emphasis>-Butylamine Borane in Polymer Solution

The process of reduction of divalent copper ions with tert-butylamine borane in dilute aqueous solutions of poly(N-vinylpyrrolidone) is investigated. The influence of polymer molecular mass on properties of the resultant Cu₂O sols is studied. It is shown that Cu₂O nanoparticles with an average diameter of 6–8 nm independent of polymer molecular mass and a relatively narrow size distribution of particles are formed in the systems under study. The contour length of macromolecules and the hydrodynamic diameter of a poly(N-vinylpyrrolidone) macromolecular coil are compared with the diameter of Cu₂O particles. Poly(N-vinylpyrrolidone) with M ≥ 1 × 10⁴ can be used to produce Cu₂O nanoparticles. Poly(N-vinylpyrrolidone) with M > 4 × 10⁴ should be used for the formation of long-living Cu₂O sols.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone copolymers with 2-aminoethyl methacrylate as drug carriers

Radical copolymerization of N-vinylpyrrolidone and 2-aminoethyl methacrylate hydrochloride has been studied. Molecular and hydrodynamic characteristics of the resulting copolymers have been determined, and their structure has been confirmed. Conditions favoring conversion of these copolymers into copolymers of N-vinylpyrrolidone with 2-aminoethyl methacrylate of different composition have been elucidated. The suitability of the prepared copolymers as polymeric carriers of monofluoroquinolone ofloxacin has been demonstrated.     

New polymer materials with controlled nanoporous structure based on N-vinylpyrrolidone

The polymer networks with nanoporous structure were obtained by the crosslinking free-radical copolymerization of N-vinylpyrrolidone with triethylene glycol dimethacrylate in bulk in the presence of amphiphilic copolymer and its fractions as templates. The templating agents consisted of copolymer or their fragments with similar monomer units and different molecular weight. Macromolecular templates were shown to be removed from the polymer composite by PrⁱOH leaving the pores. The values of the specific surface areas, the total pore volumes, pore size, and pore size distribution were measured by the method of low-temperature nitrogen absorption. The maximum value of the specific surface area was calculated to be ~26 m² g^–1. The value was significantly higher than that for the usual copolymer network. The relationship between specific surface area, parameters of pores, and macromolecular structure of template has been established. It is shown by Brunauer—Emmett—Teller method that the macromolecules having a branched architecture are more effective for the preparation of the polymer network with more developed specific surface area and narrow pore size distribution.

     

Molecular and associative properties of <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone copolymers with <Emphasis Type="Italic">N</Emphasis>-crotonoylaminocaproic acid in dilute solutions

The random copolymers of N-vinylpyrrolidone and N-crotonoylaminocaproic acid attractive for the modification of drugs are studied by static and dynamic light scattering, viscometry, and sedimentation-diffusion analysis. The content of functional groups in the copolymers is 14.1–27.0 mol %. Analysis is performed in 0.1 N aqueous solutions of sodium acetate and dimethylformamide. The molecular characteristics of the copolymers with various composition are determined. It is shown that supramolecular structures are present in copolymer solutions and their amount depends on copolymer composition; the effect of solvent on the formation of these structures is ascertained.     

Photoreduction of <Emphasis Type="Italic">o</Emphasis>-benzoquinone moiety in mono- and poly(quinone methacrylate) and on the surface of polymer matrix pores

The kinetics of photoreduction under the action of visible light of the 3,6-di-tert-butyl-o-benzoquinone moiety in methacrylic monomer, polymer, and in the graft layer on the surface of pores in the presence of different N,N-dimethylanilines has been studied. The reaction is accelerated with the increasing electron-donating ability of the amine. In the presence of N,N-dimethylaniline at 50-fold molar excess of the amine, the photoreduction in the porous polymer occurs three and four times faster than in the monomer and the polymer, respectively.     

Contrast agents for magnetic resonance imaging based on dendronized <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone polymers

In order to prepare polymeric contrast agents, various ways of modification of N-vinylpyrrolidone copolymers with vinylamine or acrolein with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid derivatives were investigated.     

Membranotropic properties of fullerene-containing amphiphilic (co)polymers of <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone

The effect of fullerene-containing amphiphilic (co)polymers of N-vinylpyrrolidone (C₆₀/PVP) differed in composition and topology of the polymer chains on the membrane structure of phosphatidylcholine liposomes was studied. Using the method of fluorescent probes it was found that the C₆₀/PVP structures under study are localized in the phosphatidylcholine membrane in the region of glycerol fragments and fatty acid chains of phospholipids. The C₆₀/PVP copolymers form complexes with 2,7-dibromoproflavin and pyrene probes. The effective equilibrium constants of the probe–C₆₀/PVP complexes in aqueous solutions and in the liposome membrane were determined. It is most likely that the fullerene-containing (co)polymers of N-vinylpyrrolidone form complexes not only with fluorescent probes but also with phospholipids of the liposome membrane, which reduces the stability of the probe–C₆₀/PVP complex.     

Free-Radical Co-Oligomerization of <Emphasis Type="Italic">N</Emphasis>-Vinylpyrroles with <Emphasis Type="Italic">N</Emphasis>-Vinylpyrrolidone: A Route to New Bioactive Oligomers

Co-oligomerization of N-vinylpyrroles (N-vinyl-2,3-dimethylpyrrole, N-vinyl-2-phenylpyrrole, N-vinyl-2,3-diphenylpyrrole, N-vinyl-2-(2-thienyl)pyrrole, and N-vinyl-2-[1-(4,5,6,7-tetrahydroindolyl) ethyl]-4,5,6,7-tetrahydroidole) with N-vinylpyrrolidone in the presence of a radical initiator (AIBN) gives co-oligomers with molecular masses of 1600–5200 in up to 87% yield. The products are readily soluble in organic solvents (benzene, 1,4_dioxane, and chloroform), and in the case of high N-vinylpyrrolidone content, also in ethanol and in water. The co-oligomers are non-toxic or have low toxicity (the lethal dose LD₅₀ = 1300–2000) and possess biological activity.     

Quantum-chemical study of the reaction of <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone with maleic anhydride

Energy profiles are calculated for the reaction of the structural isomer of N-vinylpyrrolidone with maleic anhydride in the gas phase. One of the reaction pathways leads to the formation and regeneration of maleic anhydride, acting as an activator of the process of (co)polymerization and dimerization of N-vinylpyrrolidone. According to calculations, the intermediate, isomer of N-vintlpyrrolidone, is a hybride of the singlet biradical and zwitter-ionic form.     

Copolymerization of Sodium 2-Acrylamido-2-Methylpropane-1-Sulfonate with <Emphasis Type="Italic">N</Emphasis>-Vinylpyrrolidone in Aqueous-Ethanol Solutions

The solvent effect on the kinetic parameters of synthesis and molecular characteristics of copolymers formed by homogeneous radical copolymerization of sodium 2-acrylamido-2-methylpropane-1-sulfonate with N-vinylpyrrolidone in aqueous-ethanol solutions at pH 9 and 60°C in the presence of potassium persulfate as an initiator was studied.     

Preparation and Properties of Hybrid Nanostructures of Zinc Tetraphenylporphyrinate and an Amphiphilic Copolymer of <Emphasis Type="Italic">N</Emphasis>-Vinylpyrrolidone in a Neutral Aqueous Buffer Solution

Water-soluble forms of a hydrophobic dye, zinc tetraphenylporphyrinate, are obtained via its solubilization by polymer particles of the micellar type formed by a copolymer of N-vinylpyrrolidone with triethylene glycol dimethacrylate. Hydrodynamic radii R_h and the size distribution of such particles in neutral aqueous buffer solutions are determined via dynamic light scattering. The electrochemical activity of the encapsulated dye is found, and its photochemical properties (absorption and fluorescence) are studied.     

Limiting stability temperatures for copper sols stabilized by poly(<Emphasis Type="Italic">N</Emphasis>-vinyllactams)

It has been shown that stable copper sols cannot be prepared through the reduction of copper ions in aqueous solutions of poly(N-vinyllactams) in the presence of poly(N-vinylpyrrolidone) in the temperature range 50–70°C, while in the presence of poly(N-vinylcaprolactam), the said sols cannot be prepared at temperatures below ～12°C. This tendency is related to the thermodynamic instability of complexes formed via noncovalent interactions of copper nanoparticles with polymer macromolecules in corresponding temperature ranges. Stable sols synthesized in the presence of the above polymers at other temperatures rapidly lose stability in the said temperature ranges, and this effect is accompanied by the aggregation of metal particles. The experimental results provide evidence that there is a relationship between the stability of complexes macromolecules-metal nanoparticles and the thermodynamic quality of the solvent.     

Synthesis of Copolymers of Vinylformamide with <Emphasis Type="Italic">N</Emphasis>-Methacryloylglucosamine

Copolymers of vinylformamide with N-methacryloylglucosamine were prepared. Acid hydrolysis of these copolymers yielded terpolymers of vinylformamide, vinylamine, and N-methacryloylglucosamine. A ¹H NMR study showed that the hydrolysis of the vinylformamide homopolymer under the same conditions is virtually complete.     

Copolymers of betulin esters and silver nanocomposites based on them

New biologically active silver nanocomposites based on the copolymer of lup-20(29)-ene-3,28-diol 28-O-vinylbenzoate with N-vinylpyrrolidone were prepared by the borohydride method. The formation of spherical nanoparticles with a mean diameter of 67 nm was confirmed by scanning electron microscopy. The synthesized copolymers and silver nanocomposites exhibit cytotoxic activity and show promise for the development of new materials for medical purposes.     

Nanocomposite forming on the cathode in electrochemical reduction of copper ions from a polymer solution

Copper electrodeposition from a solution of a mixture of copper(II) sulfate and poly(N-vinylpyrrolidone) is accompanied by the formation of a nanocomposite on the cathode. The nanocomposite contains copper nanoparticles and up to 20 wt % polymer. The composite forms by a noncovalent interaction of polymer macromolecules with the surface of copper particles growing on the cathode.     

Kinetics of mechanochemical dissolution of chromium in iron

The kinetics of solid Fe–Cr solution formation has been studied during mechanical alloying of Fe and Cr powders taken in an atomic ratio of 80: 20. X-ray diffraction and Mössbauer spectroscopy data have been analyzed within the framework of the energetic approach. It has been established that, in this system, reaction product yield N is related to mechanical energy dose D and specific surface area S of Fe nanograin boundaries in an ideal manner: N ~ D² at S ~ D and N ~ D at S = const.     

Linear-Dendritic Block Copolymers Based on <Emphasis Type="Italic">N</Emphasis>-Isopropylacrylamide and Perfluorinated Polyphenylenegermane: Synthesis and Properties at Various Interfacial Boundaries

It is shown that linear-dendritic block copolymers poly(N-isopropylacrylamide)–block–polyphenylenegermane can be prepared by the polymerization of N-isopropylacrylamide in the presence of bis(pentafluorophenyl)germane followed by activated polycondensation with tris(pentafluorophenyl)germane. The properties of the dilute solutions and Langmuir monolayers of the functional polymers and the linear-dendritic block copolymers of N-isopropylacrylamide are studied.     

Fabrication of macroporous protein-containing films through the reverse emulsions approach featuring <Emphasis Type="Italic">β</Emphasis>-cyclodextrin-conjugated PEG-PLGA copolymers

A series of β-cyclodextrin-conjugated 4-arm poly(ethylene glycol)-poly(lactide-co-glycolide) (4-arm PEG-PLGA) copolymers were synthesized by a ring-opening polymerization of D,L-lactide and glycolide using 4-arm PEG as initiator, and then conjugated with mono(6-ethylenediamine-6-deoxy)-β-cyclodextrin (CDen) or ethylenediamino-bridged bis-β-CD (BCDen). The chemical structures of copolymers were confirmed by ¹H-NMR and FTIR spectroscopy. The β-CD-conjugated PEG-PLGA formed stable reverse micelles due to the formation of β-CD and bovine serum albumin (BSA) inclusion complexation, which could accommodate BSA in the organic solvent with improved encapsulation efficiency. Moreover, we demonstrated a one-step approach to construct macroporous protein-containing films using these reverse micelles. The films with ordered pore arrays were directly prepared from reverse micelles. Interestingly, the protein was totally located in the whole matrix except for the pores.