Search

The structure and properties of Cu/Cu2O-containing nanocomposites formed by chemical reduction of Cu2+ ions in interpolyelectrolyte–metal complexes (IMC) at different molar ratios [NaBH4]: [Cu2+] and reduction times were studied by methods of wide- and small-angle X-ray scattering, transmission electron microscopy, thermomechanical analysis, and antimicrobial tests. Optimal conditions ([NaBH4]: [Cu2+] = 6.0, reduction time ≥ 120 min) for the formation of copper-containing nanocomposites based on interpolyelectrolyte complexes and Cu/Cu2O core–shell nanoparticles have been established by X-ray diffraction analysis. Owing to the above conditions, the structural manifestation of the metal copper phase is fully realized. Applying transmission electron microscopy, it was found that at molar ratio [NaBH4]: [Cu2+] = 6.0, and reduction time of 40 min and 180 min, accordingly, the nanocomposites with average nanoparticles size of 4.1 nm and 12.4 nm are derived from IMC, respectively, what correlates with effective size of the nanocomposites' heterogeneity regions, lp. Thermomechanical analysis has shown that raise in the amount of reducing agent or the duration of reduction of Cu2+ ions in IMC is accompanied by elevation in the glass transition temperature, which reaches a constant level, boost in the temperature of transition to the viscous state Tf and decrease in the relative deformation of nanocomposites. The antimicrobial investigations of the elaborated nanocomposites revealed they possess an antimicrobial activity against S. aureus and E. coli strains. [ABSTRACT FROM AUTHOR]

The structure and properties of silver-containing nanocomposites formed by the method of thermochemical reduction of Ag+ ions in polyelectrolyte-metal complexes pectin–Ag+–polyethyleneimine were studied using X-ray diffraction analysis, thermogravimetric analysis, pyrolysis mass spectrometry, transmission electron microscopy and antimicrobial test. The optimal parameters for the formation of nanocomposites based on interpolyelectrolyte complexes of pectin–polyethyleneimine and Ag nanoparticles (reduction temperature T = 150 °C, reduction time t = 30 min) have been found by X-ray diffraction analysis, in which the structural manifestation of the silver metal phase is fully realized. Using transmission electron microscopy, it was found that nanocomposite formed by thermochemical reduction of Ag+ ions at 150 °C for 30 min has an average nanoparticle size of 4.1 nm that less than for nanocomposite obtained at T = 120 °C during the same reduction time (average nanoparticle size is 5.8 nm). Ag nanoparticles obtained by using a typical reducing agent (NaBH4) have an average size equals 3.8 nm. It was revealed that nanocomposites obtained by thermochemical method have significantly higher antimicrobial activity compared with nanocomposites obtained by chemical reduction of Ag+ ions using NaBH4. A mechanism of thermochemical reduction of silver ions in IMC pectin–Ag+–polyethyleneimine, which is based on the transfer of electrons from the nitrogen atoms of amino groups PEI to Ag+ ions, has been investigated by destructive processes that occur at the same time. [ABSTRACT FROM AUTHOR]

By using the methods of DSC, TGA-DTG analysis, we study nanocomposites composition EP-3 % CdO and EP-3 % (CdO + PAn) cured under standard conditions in constant magnetic or electric fields. We show that these factors affect the segmental mobility of interstitial cross-linked polymer fragments and the specific heat jump. The interaction of external magnetic field only with dipole molecules of the sample EP-3 % CdO causes a partial change in its structure. Analytical processing of DSC thermograms showed that introduction of the polyaniline (Pan) and CdO 3 % vol. into epoxy matrix contributes to reduction of the specific heat capacity of epoxy (EP) in the investigated temperature range and thus causes the segmental mobility growth. PAn, introduced into the reagent mixture (EP-CdO) is forced into the interfacial organic-inorganic mixture layers and contributes to their reconciliation. These data correlate with changes in the activation energy depending on the nanocomposites composition and their curing conditions. We discover that the CdO catalytic effect influenced the pyrolysis epoxide matrix. [ABSTRACT FROM AUTHOR]

This review summarizes the basic principles of photocatalysis and parameters which influence the photocatalytic processes, involving titanium dioxide. The role of cyclodextrins is clarified and the mechanism of action of titanium dioxide in the processes ofphotodegradation is considered as well. [ABSTRACT FROM AUTHOR]

Cyclodextrin based urethane-containing polymers are synthesized and their sensor properties towards a range of organic vapors (pollutants) being possible presented in the air are studied. Nanolayers of such type polymers could be applied for development of the sensor systems for environment monitoring. [ABSTRACT FROM AUTHOR]

Involving FT-IR method and DSC (differential scanning calorimetry), peculiarities of inclusion complexes based on cyclodextrins (β-CD and HP-β-CD) and bovine serum albumine, BSA (at different molar ratios) are investigated. The results obtained could be a basis for further development and research of analogue systems based on a different proteins to be applied for medicine. [ABSTRACT FROM AUTHOR]

Water-soluble β-cyclodextrin-containing polymers on the base of trimellitic anhydride chloride (at a different molar ratio of reagents) are synthesized and their structural characteristics being studied by thermal mass-spectrometry. [ABSTRACT FROM AUTHOR]

Applying quartz crystal microbalance (QCM) method, sensor properties of carboxyl-containing cyclodextrin polymers towards ammonia vapors are studied and found out that they sensitive to that substance. Taking into account the results obtained from the kinetic curves' response, these polymer materials would be of interest for use as sensor elements for detection of a range of hazardous organic vapors and pollutants. [ABSTRACT FROM AUTHOR]

Biodegradable properties of the elaborated polyurethanes and polyamido urethanes composites based on the lactic acid and poly(lactic acid) are studied. Influence of component content and natural chain extender of polyurethane onto the biodegradation process is described. It is shown, that biodegradation increased as a result of partial or full substitution of 1,4-butandiol for lactic acid and poly(lactic acid) in polyurethane chain. [ABSTRACT FROM AUTHOR]

Thermal mass-spectrometry has been employed to investigate a process of thermal destruction of the inclusion complexes of β-cyclodextrin and (2-hydro-xypropyl)-β-cyclodextrin with Phenoxathiin. The decomposition behavior of both physical mixtures and inclusion complexes under programmed temperature rise up to 400 °C has been studied. [ABSTRACT FROM AUTHOR]

Molecularly-imprinted polymers (MIPs) involving vinylpyrrolidone, methacrylic acid, hydroxyethylmethacrylate and cross-linker - ethyleneglycol dimethacrylate have been synthesized and comparative evaluation of their sorption characteristics towards pollutants - 4-nitrophenol and phenol has been provided. [ABSTRACT FROM AUTHOR]

Thermal mass-spectrometry has been employed to investigate a process of thermal destruction of the inclusion complexes of β-cyclodextrin with 4-nitrophenol and 1,5-dichloropentane, accordingly. The decomposition behavior of both physical mixtures and inclusion complexes under programmed temperature rise up to 400 °C has been studied. [ABSTRACT FROM AUTHOR]

Thermal mass-spectrometry has been employed to investigate a processes of thermal destruction of β-cyclodextrin silyl-derivatives. The results of investigations have shown that silyl-derivatives of β-cyclodextrin are more temperaturestable than native β-CD. [ABSTRACT FROM AUTHOR]

The review is devoted to the inclusion complexes of the cyclodextrins (CDs) and their derivatives. Methods of preparation, studying and area of industrial applications for CD-based complexes are considered and summarized. [ABSTRACT FROM AUTHOR]

Synthesis of sorbents based on citrus pectin and polyethyleneimine (PEI) is carried out. Compounds obtained have PEI content ranging from 30 to 71 % w., and concentration of amino groups from 7,59 to 11,19 mmol/g, respectively. Sorption characteristics of the following ions: Cu2+, Hg2+, Zn2+, Co2+, Ni2+, Cd2+, Pb2+ depending on pH value and adsorption time were studied and shown that highest affinity they demonstrate towards Cu2+, Hg2+ and Ag+ ions. Sorption kinetics for Cu2 + ions is shown to be described by the pseudo-second order equation. [ABSTRACT FROM AUTHOR]

Thermal mass-spectrometry (TMS) has been employed to investigate a processes of thermal destruction of polyurethane compositions functionalized by β-cyclodextrin after their heat oxygen age-ing. The results of investigations showed a possibility to obtain functionalized compositions having β-cyclodextrin in amount of 5–25 % mas. which are stable to heat oxygen ageing. [ABSTRACT FROM AUTHOR]

MALDI ToF studying of modified cyclodextrins (native β-cyclodextrin and its silyl derivative) and their identification were provided. [ABSTRACT FROM AUTHOR]

The objective of this work is to study the peculiarities of structural organization, morphology, thermomechanical and antimicrobial properties of nanocomposites based on pectin-polyethyleneimine polyelectrolyte complexes and silver nanoparticles in dependence of the type of reducing agent, which was applied for chemical reduction of silver ions. It was shown that the average size of Ag nanoparticles was increased with decreasing the power of reducing agent and equals 3,8; 4,3 and 17,3 nm when using sodium borohydride, hydrazine and ascorbic acid respectively. It was found that the crystallite size of Ag also was the smallest for NaBH4 as reducing agent, although the narrowest size distribution of silver nanoparticles in the polymer matrix is observed when reducing silver ions by hydrazine. The influence of the size of silver nanoparticles in the polymer matrix on the antimicrobial activity of nanocomposites has been established. The inhibition zone diameter of Staphylococcus aureus and Escherichia coli were the highest (19 and 20 mm, respectively) for the nanocomposite obtained using hydrazine. [ABSTRACT FROM AUTHOR]

In the present work polymeric composite films materials based on polyvinyl alcohol (PVA), glycerol and silver nitrate the conducted composites with high mechanical characteristics were created. In the process of composites drying, glycerol acts as a reducing agent and the formation of silver nanoparticles occurs, moreover the reducing take places at room temperature. The AgNO3 content is varied from 0.01 to 30 wt.%. Taking into account the physical-mechanical and conducting properties of composites, it is established that the optimum content of glycerol in the final material is equal to 30 wt%. The formation of metallic silver was confirmed by an appearance of a surface plasmon resonance band at 420-430 nm in UV spectra and the appearance of two diffraction peaks at 38.17° and 44.15° in X-ray diffraction pattern as well, corresponding to the crystallographic planes (111) and (200) of a face centered cubic lattice of Ag0. Dielectric spectroscopy data show that the increasing of glycerol content up to 30-40 wt.% leads to enhance the conductivity by three orders in comparison with the initial PVA. An increase in the silver content resulted in further rise of the conductivity, reaching value of 5.72 10-6 S/cm at 15 wt.% of silver concentration, at room temperature (20 °C). At 100-120 °C, the conductivity was the highest for the composite with 25 wt.% of AgNO3 - 3.67-3.84 10-4 S/cm. The resulting samples had high physical and mechanical properties: relative elongation of about 400%, tensile strength of 32-36 MPa. Studies of the dynamic light scattering of films solution with Ag NPs showed that the smallest size was for the sample with 0.5 wt.% - 6.3 nm. [ABSTRACT FROM AUTHOR]

A literature review on the production of thermoplastic starch (TPS) with various plasticizing additives as a component of biodegradable polymer compositions was conducted. Plasticizing additives with different functional groups, due to which starch modification occurs, were analyzed. In order to expand the spectrum of functional additives for the formation of TPS, the introduction of acids with different amounts of carboxyl groups: citric, oxalic, oleic, stearic was studied. The technological parameters of thermomechanical processing of starch compositions and the quantitative composition of the components are determined. Physical and mechanical tests of strength and elasticity of film samples of TPS compositions and compatible with synthetic polymer were carried out. In order to obtain the structural characteristics of TPS and TPS films with polyethylene, studies were carried out by IR-Fourier spectroscopy and mass spectrometry. Studies of the effect of UV irradiation on the degradability of TPS compositions after exposure in a climate chamber for 90 days were conducted. It was found that the loss of strength and elasticity of TPS and TPS+PE film samples is (82-90)%, elasticity (60-70)%, depending on plasticizing and structure-forming additives and their amounts. [ABSTRACT FROM AUTHOR]

Polyelectrolyte complexes (PECs) based on sodium alginate (SA) with polyethyleneimine (PEI) were synthesized at a molar ratio of SA:PEI = 1.00:0.25 (PEC-1) and SA:PEI = 1.0:0.5 (PEC-2). The temperature intervals of thermodegradation for both the initial components and PECs were determined by pyrolytic mass spectrometry. It was shown that the molar ratio in these PECs significantly affects their swelling level in an aqueous environment as well as their mechanical characteristics. For instance, PEC-2 film is stiffer and more brittle compared to PEC-1 film, which retains flexibility. It has been revealed that PEC-2 exhibits a lower total ionic current of volatile components and a smaller number of ionic fragments generated during pyrolysis across the entire temperature range compared to PEC-1. In other words, PEC-2 is more resistant to temperature impact than PEC-1, which can be attributed to the difference in the molecular structure of the PECs. The formation of a greater number of ionic and hydrogen bonds in PEC-2, in our opinion, results in the formation of a stiffer and more ordered structure (compared to PEC-1). It is worth noting that the composition of PEC-2 is closer to stoichiometric, which leads to a decrease in the swelling degree of its film in water, and a decrease in its elasticity. [ABSTRACT FROM AUTHOR]

Thermal mass-spectrometry has been employed to investigate a process of thermal destruction of the polyolefins, modified by degradable additives under the influence of the yeast Yarrrowia lipolytica. It has been determined, that incorporation of amino-containing compound and a polysaccharide leads in increasing of biodegradation of polyolefin compositions under the influence of the above mentioned yeast. [ABSTRACT FROM AUTHOR]

By using X-ray structural analysis of polyelectrolyte complexes based on of strong anionic and cationic polyelectrolyte were investigated. By using FTIR and differential scanning calorymetry this polymer system were identificated. It was esteblished what by molar ratio 1:2 of anionic and cationic polyelectrolyte stochiometric compoun realized. For this compound maximal change axes of microheterogeneous structure of complexes realized. It was esteblished what by major concentration of cationic polyelectrolyte cristalline structure of complexes realized. [ABSTRACT FROM AUTHOR]

In the present paper the degradation of polyethylene (PE) compositions with additives of 1-5 wt % polyvinyl alcohol (PVA) plasticized with modified rape (MRo) or soybean oil (MSo) was studied. The degradability of obtained composites was evaluated by changes in physico-mechanical characteristics which take place under the influence of UV irradiation and biological factors of the soil during 120 days. It was found that the initial tensile strength of compositions with additives of plasticized polyvinyl alcohol is increased compared with the pure PE by 50-77 % (11,10-13,10 MPa). Meanwhile, after the UV exposure due to the passage of degradation processes, tensile strength was significantly reduced (up to 2-3 MPa). The action of biological soil factors has a little effect on physico-mechanical characteristics, as the result the tensile strength of the samples is reduced by only 15-24 %. The loss of elongation was similarly influenced by UV irradiation and decreased up to 90 % of the original value, which was within 40-80 %. The pyrolysis mass spectrometry was also used to describe the processes which occur during sample aging. It is shown that the functional additives based on plasticized PVA induce the structural transformations were assessed by the change of quantity and intensity of ion fragments. For instance, the intensity of ion fragments for PE-MSo decreased by 7-96 % after the UV exposure and 9-42 % after the aging of composite in the soil. [ABSTRACT FROM AUTHOR]