The self-assembly and gelation processes in low-concentrated aqueous solutions of L-cysteine and silver nitrate (cysteine–silver solution, CSS); low-molecular-weight water-soluble chitosan (CS); and a gelation initiator, CuSO4, have been studied by various physicochemical methods, namely, UV spectroscopy, dynamic light scattering, pH-metry, viscometry, and scanning electron microscopy. It has been found that the gelation of CSS, which is used as a gel precursor, under the action of chitosan (CS) and copper sulfate occurs in a narrow concentration range: CCH = 0.0100–0.0150 mg/mL, C_CuSO_4 = 0.4–0.6 mМ, CL-cys = 3.00 mМ, and C_AgNO_3 = 3.75 mM, when Ag+/Cys molar ratio is 1.27. Hydrogels of various CSS–CS and CSS–CS–CuSO4 compositions possess no high mechanical strength; however, they are stable in the course time. The structural elements of CSS, i.e., cluster chains of silver merchaptide (SM) zwitterions, are positively charged; therefore, no polyelectrolyte complexation occurs in CSS–CS and CSS–CS–CuSO4 hydrogels, because the pH of CSS is 2.6. Addition of CuSO4 to CSS–CS samples promotes the formation of a more strong hydrogel due to the association of SM clusters and CS molecules with sulfate anions and the coordination of Cu(II) ions with deprotonated carboxyl groups of different clusters.

The object of the study were samples of fibers obtained from ultrahigh-molecular-weight polyethylene (UHMWP) gel with different multiplicity of stretching (λ) with a scatter (dispersion) of mechanical properties. It is shown that the dependence of strength (σb) on breaking elongation (ε) of the studied samples is expressed by the equation σb = σb0 + K·ε and appears as a series of variously inclined straight lines specific for each λ value, which converge upon extrapolation to ε = 0 to a single point (pole), the ordinate of which coincides with the strength of unoriented fiber (σb0). With increase of λ the straight lines representing the course of the relationships σb(ε) shift toward low ε values. The decrease of ε is compensated abundantly by increase of angular coefficient K, which determines the degree of effect of ε on σb.

ИССЛЕДОВАНИЕ ПРОЦЕССОВ ГЕЛЕОБРАЗОВАНИЯ В ЦИСТЕИН-СЕРЕБРЯНОМ РАСТВОРЕ ПРИ ДОБАВЛЕНИИ СУЛЬФАТОВ МЕТАЛЛОВЯ.В

В работе впервые реализован одностадийный способ гелеобразования в водных системах на основе аминокислоты L-цистеин (L-Cys), нитрата серебра и иодида калия. Получены прозрачные, устойчивые во времени гидрогели с молярным соотношением компонентов Ag/L-Cys в диапазоне 1,5-2,0 при постоянной концентрации KI ± 0,75мМ. Процесс гелеобразования в водных системах L-цистеин-AgNO-KI исследован c помощью методов вискозиметрии, спектроскопии УФ-видимого диапазонов, динамического светорассеяния (ДСР), просвечивающей и сканирующей электронной микроскопии (ПЭМ и СЭМ). Установлено, что процессы самосборки и гелеобразования в низкоконцентрированном водном растворе L-цистеина и AgNO (ЦСР), инициированные высокоселективным иодид-анионом, зависят, главным образом, от содержания соли серебра. One stage (one pot) gelation in aqueous solutions of the amino acid L-Cysteine, silver nitrate and potassium iodide is realized for the first time. Transparent, stable over time hydrogels with molar ratio of Ag/L-Cys in the range of 1,5-2,0 and concentration of KI equal to 0,75 мМ are synthesized. Gelation in L-Cys-AgNO-KI solutions is studied by viscometry, UV spectroscopy, dynamic light scattering (DLS), transmission and scanning electron microscopy (TEM and SEM). It is established that self-assembly and gelation in supramolecular L-cysteine-silver solution initiated by highly selective iodide anion depend mainly on silver salt concentration.

Using the methods of viscometry, dynamic light scattering (DLS), Fourier-IR and UV spectroscopy, as well as scanning electron microscopy (SEM), the self-assembling processes in systems based on low-concentrated aqueous solutions of glycine and silver nitrate [glycine–silver solution (GSS)], and polyvinyl alcohol (PVA) were studied. GSS–PVA films were obtained by casting from a solution. During the formation of films, the manifestation of a yellow color was discovered and its intensification during storage of the films, which is due to the processes of reduction of silver in the form of nanoparticles.

ПРИМЕНЕНИЕ МЕТОДА УФ-СПЕКТРОСКОПИИ ДЛЯ ИЗУЧЕНИЯ СТРУКТУРНЫХ ПЕРЕСТРОЕК В

Composite films containing >0.5% polymer could be produced from mixed aqueous solutions of poly(vinyl alcohol) (PVA), simple amino acids (glycine and L-cysteine), and silver nitrate by casting in Petri dishes followed by drying at 30ºC. The viscosity characteristics of the mixed solutions and the mechanical properties of films produced from these solutions were studied as a function of the PVA concentration. A supramolecular gel with thixotropic properties formed with a low PVA content (≤0.1%) in the solution while the thixotropic properties disappeared and the ability to produce films appeared for concentrations ≥0.5%. The higher the polymer content in the solution and film was, the higher their viscous and stress-strain properties were. The structures and properties of the mixed solutions and hydrogels and films prepared from aqueous solutions of glycine, PVA, and silver nitrate were studied using viscometry, UV spectroscopy, dynamic light scattering, scanning electron microscopy, and elemental analysis. The presence of glycine in the solution and gel was observed to reduce the viscosity because it weakened the H-bonding between polymer macromolecules. Films that were very light sensitive with respect to formation of silver nanoparticles could be produced at PVA solution concentrations of 5% and greater, like for films based on L-cysteine and silver nitrate.

Magnesium aluminate spinel (MgAl2O4) ceramics have been subjected to hot isostatic pressing. The process led to a 0.28

The processes of self-organization of a cysteine–silver solution and the effect of heating and ultraviolet radiation on the self- organization and formation of silver nanoparticles were studied using UV spectroscopy. The key factor influencing the formation of silver nanoparticles is UV radiation. Heating the cysteine–silver solution to 60°C does not affect the formation of silver nanoparticles.

The work presents the results of green synthesis (biosynthesis) of silver nanoparticles using aqueous extracts of maple and oak leaves. The efficiency of the synthesis, size and shape of the formed nanoparticles were studied using UV-visible spectroscopy, dynamic light scattering, atomic force microscopy and scanning electron microscopy techniques. It was found that the formation of silver nanoparticles is accompanied by the appearance of a plasmon resonance band in the electronic spectra of aqueous extracts, the maximum of which depends on the concentration of silver nitrate and is in the range of similar to 420-429 nm in the spectra of maple leaves, and in the spectra of oak extracts there is a shift towards longer wavelengths similar to 425-435 nm, which correspond to the formation of nanoparticles of larger size. According to the dynamic light scattering data, the size of nanoparticles in the maple extracts is of about 60-68 nm and in the oak samples of similar to 107 nm. The differences in the size and shape of nanoparticles obtained in the maple and oak phytoextracts detected by atomic force microscopy and scanning electron microscopy are explained by the different composition of bioactive substances in the plants involved in the reduction of silver ions and stabilization or modification of the surface of silver nanoparticles.

The morphology of latexes (aqueous solutions of spherical polystyrene particles with carboxyl and amino groups on the surface) was studied using UV and IR spectroscopy, scanning electron microscopy (SEM), and dynamic light scattering (DLS). The histograms of the size distribution of polystyrene particles were built using SEM images of the latexes. Similar size distribution curves for polystyrene latexes were obtained using IR and UV spectroscopy. The data of IR and UV spectroscopy and independent methods such as SEM and DLS are in good agreement.

Using the provisions of the kinetic (thermofluctuation) theory of fracture of solids (Zhurkov theory) and the results of mechanical measurements it is shown that for samples of untwisted ultrahigh- molecular-weight polyethylene fiber made under identical conditions, but having scatter (variation) of mechanical properties, the strength values and other parameters resulting from the destructive process are in direct proportional dependence on the breaking elongation. The less the breaking elongation of the samples, the lower their strength. At the same breaking elongation, the strength tends to increase in proportion to the decrease in linear density of the samples.

Processes of self-organization and gelation in a low-concentration aqueous solution of l -cysteine and silver nitrate were studied using singly, doubly, and triply charged metal chlorides as gelation initiators. According to the results of studies by viscometry and scanning electron microscopy, the rheological and morphological characteristics of gels directly depend on the chemical nature and charge of the metal. This correlates well with the results of dynamic light scattering studies and zeta-potential measurements of particles responsible for the formation of the spatial gel network. IR spectroscopic analysis confirms the possibility of the interaction between the metal cations and the surface of particles forming in the solution, their binding to each other, and further gel formation. A possible mechanism of gel formation in this system is proposed based on an integrated approach.

Керамика из алюмомагниевой шпинели MgAl 2 O 4 подвергалась высокотемпературному изостатическому прессованию. Процедура привела к увеличению плотности керамики на 0.28% по сравнению с образцами, полученными первичным горячим прессованием. Методом ИК-спектроскопии оценены структурные изменения в уплотненном материале. В ИК-спектре отражения, записанном в области 40–1000 см –1 , увеличение плотности проявилось в уменьшении интенсивности ряда полос изолированных колебаний, локализованных в тетраэдрах MgO 4 и AlO 4 . Эффект отнесен смешению колебаний в тетраэдрических структурных единицах в уплотненной керамике. Этот результат показал, что консолидация материала происходит с увеличением внутренней связности кристаллитов. В то же время валентные колебания групп Al–O в октаэдрах AlO 6 сохранили частоту и интенсивность после изостатического прессования, что свидетельствует об отсутствии наведенных термообработкой стехиометрических искажений.

ИССЛЕДОВАНИЕ СУПРАМОЛЕКУЛЯРНЫХ СИСТЕМ НА ОСНОВЕ НИЗКОКОНЦЕНТРИРОВАННЫХ РАСТВОРОВ L-ЦИСТЕИНА И АЦЕТАТА СЕРЕБРА ПРИ ДОБАВЛЕНИИ РАСТВОРА ЩАВЕЛЕВОЙ КИСЛОТЫ Д