A number of aminoamides of butanoic and pentanoic acids were obtained by the acylation reaction of N,N-dimethylaminoalkylamines. The activity of the synthesized aminoamides in the hardening reaction of commercial epoxy resin ED-20 was studied. Based on the data of differential thermal analysis and IR Fourier spectroscopy, as well as taking into account the content of the gel fraction in the hardened compositions, it was found that the activity of the hardener increases as the length of the hydrocarbon chain in the diamine fragment increases and the overall nitrogen content in the aminoamide molecule decreases.

Sorption properties of thiocarbamoylated polyethylene toward silver(I) from multicomponent solutions have been studied. The synthesized sorbent has been found to exhibit a high sorption capacity and selectivity toward silver ions. In static sorption mode, quantitative extraction is possible from solutions with Ag(I) concentration of 1 × 10–4 mol/L in pH range from 1 to 7, concomitant Ca(II), Mg(II), Cu(II), Fe(III), Zn(II), Cd(II), Ni(II), Mn(II), Co(II), and Pb(II) have no effect on the recovery degree of silver ions. High sorption selectivity retains under dynamic conditions in the presence of excess amounts of base metal ions at pH 2. Full dynamic sorption capacity for silver is 0.35 mmol/g (solution flow rate 2 mL/min, pH 2, sorbent weight 0.1 g, C_Ag^ + = 1 × 10–4 mol/L). The composition of eluents to provide the highest values of silver desorption degree from sorbent surface has been determined. It has been found that the silver capacity of the sorbent slightly decreases after sorption–desorption stage.

Sorption properties of poly(3-aminopropylsilsesquioxanes) modified with thiourea groups were studied to predict the possibility of using poly(n-thiocarbamoyl-3-aminopropylsilsesquioxanes) (TCPS) in separation and concentration techniques. The sorbents were synthesized by the sol-gel method followed by solid-phase modification using ammonium thiocyanate or thiosemicarbazide as modifiers. It was established that sorbents with the highest content of thiocarbamide functional groups (modified with ammonium thiocyanate) enabled quantitative and selective recovery of Ag (I) from strongly acidic solutions. The degree of Ag (I) recovery slightly decreases at pH>5, which is associated with increasing competitive sorption of Cu (II), Ca (II), Mg (II), Mn (II) and Fe (III). The highest recovery of Ag (I) for TCPS-0.63 and TCPS-0.68 was achieved at pH ranging from 4 to 8 (degree of recovery was 55–68% (TCPS-0.63); 21–26% (TCPS-0.68 )); at the same time, there was a predominance of competitive sorption of Ca (II), Mg (II), Mn (II), and Fe (III). Based on the aforementioned, it can be concluded that the sorbents modified with ammonium thiocyanate are characterized by high concentration of attached thiocarbamide groups that make them suitable for the selective recovery of Ag (I) ions from multicomponent solutions at pH 1–2.

The aim of this study is to investigate the mechanical properties of coatings based on ED-20 epoxy resin, manufactured with polyethylenepolyamine or polyamidepolyamine used as hardeners. Instrumented indentation with a Berkovich triangular pyramid is used to determine the mechanical properties. Indentation hardness, reduced elastic modulus, and creep at a given holding time are used as the characteristic parameters. The results testify that the mechanical properties of the epoxy coatings made with different hardeners differ significantly from each other and demonstrate different behaviors.

The regularities of the effect of a complex stress state on the strength of an AlMg5/epoxy adhesive joint are experimentally studied at −50 and +23 °C in tension+shear and compression+shear tests with different normal-to-shear stress ratios. The tests use modified Arcan specimens and Brazil-nut-sandwich specimens, with the lateral faces of the adhesive layer having a shape of a mushroom-like “ridge” aimed at reducing stress concentration at the specimen edges. An original computational model of a selected microvolume including the interface together with the adjacent substrate and adhesive layers is used to process the experimental results. The attainment of the threshold value of strain energy density in the selected microvolume, W*, is used as the failure criterion. The effect of the hardener composition, the testing temperature, and the value of the phase angle β determining the proportion of normal and shear stresses at the adhesive interface on the threshold value W* is detected. W*(β) diagrams (fracture loci) are plotted and analytically described logarithmic functions. They can be used to make strength calculations for adhesive joints in structures and metal-polymer composites.

Министерство науки и высшего образования Российской Федерации Российская академия наук Научный совет по неорганической химии РАН Научный совет по аналитической химии РАН Научный совет по химической технологии РАН Российское химическое общество имени Д.И

The accumulation of electronic waste (e-waste) on the ground leads to environmental pollution with toxic metal ions, which subsequently harms all living organisms. Many countries still use hydrometallurgical or manual methods to extract silver ions from e-waste. These methods are unsustainable and highly toxic; therefore, it becomes necessary to introduce new environmentally compatible methods for separating valuable components from objects of various compositions. This article proposes an environmentally compatible method for the extraction of silver ions from multicomponent systems using poly(N-thiocarbamoyl‑3-aminopropylsilsesquioxane). The sorbent surface was studied by Fourier-transform infrared spectroscopy using an attenuated total internal reflection accessory. The concentration of grafted thiourea groups is 1.39 mmol/g according to elemental analysis. It has been determined that this sorbent is capable of quantitatively extracting silver ions in the pH range from 0 to 6 at a concentration of silver ions in the initial solution of 1·10–4 mol/dm3; the static sorption capacity for silver ions under experimental conditions reaches 1.22 mmol/g. When sorption is carried out in dynamic mode, the value of the dynamic capacity before breakthrough is 0.046 mmol/g, and the value of the total dynamic capacity for silver ions is 0.132 mmol/g. The highest desorption (71–78 %) is achieved using sulfuric acid solutions with a thiourea concentration gradient.

A series of N,N-dimethylaminoalkylamides of perfluorobutanoic and perfluoropentanoic acids were prepared, and the activity of these amides in curing of ED-20 commercial epoxy resin was studied. Data of differential thermal analysis and Fourier IR spectroscopy, taking into account the gel fraction content of the cured composites, show that the curing agent reactivity increases with an increase in the weight fraction of the hydrocarbon moiety and with a decrease in its fluorine content. Evaluation of the adhesion strength in gluing St.3 steel with amide-cured ED-20 epoxy resin shows that all the compounds synthesized ensure two times more efficient gluing compared to the resin cured with the standard curing agent, polyethylenepolyamine. In gluing of D16 aluminum alloy, the gluing efficiency, on the contrary, slightly decreases.

The paper studies the adhesive strength of aluminum alloy specimens bonded with the use of an epoxy adhesive, under the tensile-shear stress state, depending on the testing temperature. Tension of modified Arcan specimens with load angles of 0, 22.5, 45, 67.5, and 90° with respect to the plane of adhesion is chosen as the experimental method. Experiments were performed at temperatures of −50, +23, and +50 °С. The analysis of the obtained results yields a linear fracture criterion and a fracture locus for the adhesive failure strain energy density, which takes into account the ratio of the elastic properties of the adhesive to those of the substrate. The region bounded by the fracture loci of adhesive strength and ultimate strain energy density determines the conditions for the safe loading of the bonded assembly in terms of the energy and force criteria of adhesive failure. The proposed fracture loci can be used, preferably simultaneously, to estimate the in-service strength and reliability of adhesively bonded assemblies.

Mesoporous carbon of lamellar morphology was synthesized by the thermal decomposition of zinc glycerolate in an inert atmosphere followed by the removal of zinc oxide from the ZnO/C composite. The obtained material was characterized by scanning electron microscopy, Raman spectroscopy, and low-temperature adsorption of nitrogen. Mesoporous carbon is remarkable for a high adsorption rate of methylene blue dye from aqueous solutions with the maximum adsorption capacity toward the dye equal to 1680 mg g−1.

Polysiloxanes containing nonchelating 3-aminopropyl and chelating N-(2-aminoethyl)-3-aminopropyl groups with the degree of functionalization of 28 and 24%, respectively, were prepared by sol–gel synthesis. The polysiloxanes obtained showed comparable activity in sorption of Pd(II), Pt(IV), Fe(III), Cd(II), Zn(II), Co(II), Ni(II), Cu(II), Mn(II), Pb(II), Ca(II), and Mg(II) ions from model multicomponent solutions. At pH < 3,3-aminopropylpolysiloxane selectively takes up platinoid ions. The chelating structure of N-(2-aminoethyl)-3-aminopropyl groups leads to a decrease in the selectivity of the interaction with Pd(II) ions but increases the affinity for Fe(III), Ni(II), and Cu(II). Preconcentration in the dynamic mode allows quantitative sorption of Pd(II) and Pt(IV), followed by virtually quantitative elution of the metal ions from the sorbent surface.

Synthesis and study of the physicochemical properties of silsesquioxanes modified with 3-aminopropyl, 2-aminoethyl-3-aminopropyl, and dithiooxamide groups was carried out. The obtained sorbents were characterized by thermal stability, porosity, and a high degree of functionalization; the concentration of groups grafted to the particle surface reached 2.80 mmol g−1. Modified silsesquioxanes were used as an electroactive substance for the development of indicator carbon paste electrodes (CPEs). When using a CPE with a 5% dithiooxamidated silsesquioxane content, the conditions selected for potentiometric titration of aqueous solutions containing silveri were pH 3–4, the titrant was potassium iodide. The designed sensor was successfully tested by analyzing a standard sample and a drug for silver ion content.

In order to increase the affinity of the halloysite mineral to 3d-metal ions, its surface was functionalized with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane. A significant influence of the nature of the solvent and silane concentration on the degree of functionalization of halloysite was revealed. According to the data of elemental analysis, FTIR spectroscopy, and thermogravimetry, it was found that the most efficient solvents were tetrahydrofuran and acetonitrile at an equimolar silane to halloysite ratio. The functionalization of halloysite with N-(2-aminoethyl)-3-aminopropylsilyl groups significantly increases the sorption capacity of the material in comparison with both unmodified halloysite and halloysite functionalized with non-chelating 3-aminopropylsilyl groups.

Halloysite is modified with 3-aminopropyltriethoxysilane in various solvents without pretreatment. According to elemental analysis, FTIR spectroscopy, and thermogravimetry, the reaction between 3‑aminopropyltriethoxysilane and halloysite successfully proceeds regardless of the nature of the solvent. The maximum degree of functionalization of interaction products is achieved at the equimolar silane : halloysite ratio; as this value is increased, the degree of functionalization decreases. The magnitude of the degree of hydrolysis changes symbatically with the degree of functionalization.

New adhesive materials based on a single-part hot-cured epoxy adhesive for forming corrosion-protective coatings were obtained. Perfluoropentanoic acid N-methylpiperazide and polyethylenepolyamine were used as curing catalysts. The adhesive compounds in the cured state were characterized by the degree of swelling, gel fraction content, Vickers hardness, elastic modulus, and creep strain; their corrosion-protective properties with respect to low-carbon steel (St. 3) and aluminum–magnesium alloy (AMg-6) were determined. The chemical structure of the organic solvent and amine curing agent largely determines the operation characteristics of the coatings obtained.

Anodic aluminum oxide (AAO) membranes are versatile nanomaterials that combine the chemically stable and mechanically robust properties of ceramics with homogeneous nanoscale organization that can be tuned to desirable pore diameters and lengths. The AAO substrates feature high surface area that is readily accessible to large and small molecules, making these nanostructures uniquely suited for many possible applications. Examples include templated self-assembly of macroscopically aligned biological membranes and substrates for heterogeneous catalysis. For further development of such applications, one would like to characterize and tune the electrostatic properties of the inner pore surface as well as the local acidity within the nanochannels. Here, we employed electron paramagnetic resonance (EPR) spectroscopy of a small molecule - ionizable nitroxide - as a reporter of the average local acidity in the nanochannels and the local electrostatic potential in the immediate vicinity of the pore surface. The former was achieved by measuring EPR spectra of this molecular probe diffusing in an aqueous phase confined in the AAO nanochannels while for the latter the nitroxide was covalently attached to the hydroxyl group of the alumina surface. We show that the local acidity within the nanochannels is increased by as much as.1.48 pH units vs. the pH of bulk solution by decreasing the pore diameter down to ca. 31 nm. Furthermore, the positive surface charge of the as-prepared AAO could be decreased and even switched to a negative surface charge upon annealing the membranes first to 700 degrees C and then to 1200 degrees C. For as-prepared AAO, the local electrostatic potential reaches psi = (163 +/- 5) mV for the nitroxide label covalently attached to AAO and located about 0.5 nm away from the surface. Overall, we demonstrate that the acid-based properties of the aqueous volume confined by the AAO nanopores pores can be tuned by either changing the pore diameter from ca. 71 to 31 nm or by thermal annealing to switch the sign of the surface charge. These observations provide a simple and robust means to tailor these versatile high-surface-area nanomaterials for specific applications that depend on acid-base equilibria.

We studied the vocal repertoire and acoustic activity of short-tailed voles in experiments. Three acoustic signals of short-tailed voles: sharp and quiet squeaks emitted by males and females, and singing by males were recorded and analyzed. We compared such parameters as duration, fundamental frequency, modulation depth, quartiles and dominant frequency. The parameters of quiet and sharp squeaks overlapped completely and form a continuum. The quiet squeaks of female and male songs could be emitted in series. Singing and quiet squeaks showed some differences in frequency parameters: fundamental frequency and three quartiles of singing were higher than those of quiet squeaks. Acoustic behavior of the short-tailed vole was investigated in 6 experimental groups. Voles emitted squeaks in 11.4% interactions, and males sang in 1.7% interactions (the number of contacts totaled, n = 1792). In same-sex interactions we registered squeaks, mostly during aggressive contacts and refuge defense. In the opposite-sex interactions, voles squeaked during friendly or neutral contacts, and during refuge defense. Males were singing during friendly and sexual contacts with females.