Organic Dispersant Media Research Articles

Wound Coating Collagen-Based Composites with Ag Nanoparticles: Synthesis, Structure and Biological Activity

The search for materials for a new generation of wound coatings is important due to the increase in antibiotic-resistant microorganisms and the number of patients with untreatable chronic purulent wounds. Metal nanoparticles, specifically silver nanoparticles, have antimicrobial activity and do not induce known bacterial resistance. To obtain new Ag-containing nanocomposites, type I collagen was extracted by an enzyme–acid method from cattle tendons. Silver nanoparticles were obtained by an environmentally safe method, metal-vapor synthesis (MVS), which enables obtaining metal nanoparticles without impurities. For this, metal vapors were cocondensed in a vacuum of 10−2 Pa on the walls of a quartz reactor cooled to 77 K using acetone as an organic dispersion medium. The composition of the collagen surface was determined by XPS using the spectra of C1s, N1s, and O1s. The presence of a peak with a binding energy of approximately 368.57 eV in the Ag 3d5/2 spectrum indicates the state of Ag0 silver atoms in the nanocomposite. SEM images showed that collagen contributes to the effective stabilization of Ag nanoparticles with an average size of 13.0 ± 3.5 nm. It was found that collagen is non-toxic and biocompatible with skin cells and fibroblasts. The collagen–Ag nanoparticle nanocomposites exhibited antimicrobial activity against bacteria Bacillus subtilis, Escherichia coli, and fungi Aspergillus niger.

XPS study of silver and copper nanoparticles demonstrated selective anticancer, proapoptotic, and antibacterial properties

Silver and copper nanoparticles were produced by an ecologically safe metal vapor synthesis (MVS) method using acetone as an organic dispersion medium. Transmission electron microscopy (TEM) showed that the specimens are spherical and polydisperse, and their average size is 2.5 nm for silver nanoparticles (Ag NPs) and 2.6 nm for copper nanoparticles (Cu NPs). X‐ray photoelectron spectroscopy analyses showed that the state of silver in the nanoparticles is close to that of silver in the Ag0 state, whereas copper black contains two oxidized states of the metal—Cu+ and Cu2+. Biological in vitro studies demonstrated that the nanoparticles have antibacterial activity against Gram‐positive and Gram‐negative bacterial species. Cu NPs exhibited more prominent antibacterial effects and induced significant growth inhibition of Bacillus cereus and Escherichia coli. Both types of nanoparticles showed anticancer properties in vitro. Cu NPs induced intense cytotoxicity in cancer and normal fibroblasts in vitro cultures, but their inhibitory effect against noncancerous cells was milder compared with cancer cell lines. Ag NPs demonstrated selective cytotoxicity against human lung and cervical adenocarcinoma cell lines. Further in vitro studies indicated that the mechanism of Ag NPs and Cu NPs anticancer effects involves induction of apoptosis. The present study describes a green synthesis approach for production of biologically active silver and copper nanoparticles and highlights their potential for medical application.

In Ukrainian

Man-caused load on sources of industrial and domestic water supply, which causes the discharge of insufficiently treated wastewater, is one of the great environmental problems in Ukraine. The traditional way of solving this problem, associated with the disposal of such waters by adsorption, membrane or catalytic technologies, has a number of disadvantages associated with large volumes and a wide range of pollutants, traditional methods often require preparatory measures, time-consuming, scarce materials and expensive equipment. It would be ideal to create waste-free circulating water supply technologies, but these options are still far from being mass-produced. A promising way to solve these problems is to organize such production cycles, where the disposal of toxic wastewater will be combined with recovery technologies. Industrial and domestic wastewater often contains a significant proportion of the organic component. These are oil products, by-products of organic synthesis, spent lubricating and cooling suspensions, waste from the food, alcohol and pulp and paper industries, dyes and pigments, etc. All this waste is energy saturated and can be separated and used as fuel. However, due to low concentrations in most wastewater, their separation is economically unprofitable. A method is proposed for neutralizing toxic organic wastewater by using it as a dispersion medium for composite coal-aqueous fuel (CAF). The possibility of priming carbon microparticles obtained by preliminary plasma-chemical treatment of an organic dispersion medium to stabilize composite coal-water fuel were investigated. Waste cutting fluid (JCL) was used as an organic dispersion medium; anthracite served as the dispersed phase. A CAF sample was obtained based on anthracite from Ukrainian deposits with a solid phase (W) content of 70 mass. %, and studied its electrokinetic and rheological properties. It has been found that the preliminary plasma-chemical conversion of organic wastewater used as a dispersion medium for composite water-coal fuel significantly improves the operational properties of CAF. The growth of sedimentation stability and the optimization of the effective viscosity are achieved mainly through the implementation of the structural and mechanical factor by increasing the number of contacts with the introduction of a highly dispersed fraction of carbon microparticles and increasing the electrostatic repulsion of the elements of the suspension structure. Thus, the sedimentation stability of the obtained CAF is significantly improved in comparison with conventional anthracite suspensions in organic wastewater and reaches 2 days without the addition of stabilizers. In the future, it is planned to further improve the properties of CAF by introducing stabilizing reagents and dispersants into its composition.

Sol–gel transition and rheological properties of silica nanoparticle dispersions

Possible variants of the rheological behavior of silica model dispersions have been analyzed. Different types of interaction between the particles and a dispersion medium make it possible to obtain different systems from low-viscosity sols to gels. Proton-donor (water) and aprotic (dimethyl sulfoxide) media have been used for comparison. Dispersions in the aprotic medium behave as non-Newtonian viscous fluids exhibiting shear thinning or shear thickening depending on deformation rate. Aqueous dispersions are viscoelastic and viscoplastic objects that exhibit the shear thickening at stresses higher than the yield stress. The introduction of small amounts of poly(ethylene oxide) into the organic dispersion medium initiates gelation. An increase in the polymer content in the dispersion medium above the concentration corresponding to the formation of a macromolecular network promotes an increase in stiffness and strength of the gels. The rheological behavior of gels is influenced by the polymer molecular mass and its affinity for a solvent.

Preparation of water-free PEDOT dispersions in the presence of reactive polyisoprene stabilizers.

Poly(3,4-ethylenedioxythiophene) nanoparticles with narrow size distribution were prepared in organic dispersant media in the presence of both iron(III) dodecylbenzenesulfonate {Fe(DBS)3}-acting as both an oxidant and a stabilizer-and ω-functionalized polyisoprenes (ω-R-PI) as costabilizers. The effects of the solvent nature and concentration of Fe(DBS)3 on the size and morphology of the PEDOT particles were first studied in the absence of costabilizer. Second, the effects of the molar mass, concentration, and nature of the functional end group of the polyisoprene costabilizer were investigated. PEDOT nano-objects were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and conductivity measurements.

Organofilization of Smectite Clay from Pedra Lavrada, PB, with Nonionic Surfactant

The petroleum industry has been investing for many years in the use of smectite as dispersant agent in the composition of oil-based and water-based fluids for drilling oil wells. The State of Paraíba is one of the largest producers of such clays and new deposits have been recently discovered in the regions of Cubati and Pedra Lavrada, causing many expectations for the expansion of the national mineral production. The objective of the present work is the organofilization of smectite clay from Pedra Lavrada, PB, through the addition of nonionic surfactant. After organofilization, the clay was characterized through X-ray diffraction and Foster swelling, so that the most suitable surfactant could be chosen for diesel as organic dispersant media. The results show that the incorporation of the surfactant used with the clay caused a significant increase in the interlamellar distance, and that the dispersions presented rheological properties that meet Petrobras' specifications for the use of organoclays in non aqueous based drilling fluids. Keywords: Smectite, drilling fluids, organofilization.

Effect of organic and aqueous dispersion medium on the development of polystyrene nanoparticles in nanoprecipitation method

The purpose of this study is to develop polystyrene nanoparticles using nanoprecipitation method. Formation of nanoparticles from pre-polymer by nanoprecipitation is a beneficial technique involving the diffusion of polymer phase into dispersion phase. However, selection of solvent /non-solvent couple has intensive influence on nanoprecipitation of specific polymer. In this study the potential of chloroform (CHCl3) and tetrahydrofuran (THF) is explored as the solvent for polystyrene. Effect of dispersion phase; methanol, chloroform, acetone and water have been investigated on nanoprecipitation of polystyrene. It was found that the addition of surfactants enhanced the stability of nanoparticles.Tween-40 has a more pronounced stabilizing effect than Pluronic F-68 on polystyrene nanoparticles in aqueous phase. More stable nanoparticles of polystyrene were obtained in the aqueous medium containing 2-g/L of Tween-40. Interface interaction of mixing phases and surface active agents affect the size and stability of nanoparticles in nanoprecipitation.

Study of Compatibility between Organoclays and Organic Dispersant Media through Foster Swelling

Foster swelling is one of the methods used to determine the compatibility between organoclays and organic dispersant media, improving the quality of organoclays. The need for replacing imported clays by national ones for the oil industry has recently resulted in the discovery of new deposits of smectites in the cites of Cubati and Pedra Lavrada, PB, reflecting great social and economic effects for that region. So, the objective of this work is to obtain organoclays from smectites from Pedra Lavrada, PB, aiming at the study of how to make these clays suitable with some organic dispersant media through Foster swelling. After organofilization, the clays were characterized by X-ray diffraction and Foster swelling. The results pointed that some media are compatible with organoclays, being diesel, kerosene and varsol the descendant order of compatibility between the clays and the organic media.

Hydroxy and Di‐Hydroxy End‐Capped Polybutadiene as Reactive Steric Stabilizers for the Synthesis of Polyurethane Particles in Organic Dispersant Media

AbstractSummary: The synthesis of polyurethane particles by polyaddition of ethylene glycol (EG) and tolylene‐2,4‐diisocyanate (TDI) in cyclohexane at 60 °C was investigated in the presence of ω‐hydroxy and ω,ω′‐dihydroxy polybutadiene, used as reactive steric stabilizers. The effect of the functionality and concentration of the reactive polybutadiene, as well as the monomer addition procedure, onto the polyurethane particle formation was studied. Calibrated PUR particles with an average diameter in the range 1–2 µm could be readily obtained.

Synthesis of Core‐Shell Polyurethane‐Polydimethylsiloxane Particles by Polyaddition in Organic Dispersant Media: Mechanism of Particle Formation

AbstractCore‐shell polyurethane (PUR)‐polydimethylsiloxane (PDMS) particles were prepared by polyaddition between ethylene glycol and tolylene‐2,4‐diisocyanate in cyclohexane, used as the organic dispersant phase, in the presence of reactive hydroxy‐terminated polydimethylsiloxane steric stabilizers. The reaction extent and the PUR particle size, monitored by FTIR, 1H NMR, SEC, SEM and TEM techniques against time, were found a function of the PDMS concentration, functionality and molar mass. A mechanism of the polyurethane particle growth is proposed on the grounds of the kinetic investigation.

Water Transport by Nanodispersion Droplets in a Water-in-Oil Emulsion

The mechanisms of water transport through an organic dispersion medium are considered for an emulsion during Ostwald ripening and for a three-phase system upon a contact of a water-in-oil emulsion with an external aqueous phase. Electron microscopy shows a formation of nanodispersion droplets during the diffusion of water through the organic phase of water-in-oil emulsions. The experimental water diffusion coefficient during Ostwald ripening in emulsions is 40 times smaller than the calculated molecular diffusion coefficient. The experimental diffusion coefficients are determined for rhodamine C, which solubilizes in the surfactant micelles, and for ethyl alcohol, a cosurfactant, which reduces the interfacial tension in the emulsion and promotes the formation of nanodispersion droplets. The experimental diffusion coefficients of rhodamine C and ethanol are three orders of magnitude smaller than the calculated values. The ratio between the numbers of rhodamine C and water molecules diffusing through the organic phase is 1 : 10 000. The nanodispersion droplets are shown to make the main contribution to the water transport in the organic dispersion medium of the emulsions. Water can also be transported by single surfactant molecules, but this mechanism is not the predominant one.

Synthesis of uniform polyurethane particles by step growth polymerization in a dispersed medium

Polyurethane microspheres were prepared by polyaddition of ethylene glycol (EG) and tolylene-2,4-diisocyanate (TDI) at 60 °C in cyclohexane as the organic dispersion medium, in the presence of dibutyl tin dilaurate (DBTDL) as catalyst and poly(styrene)-b-poly(ethylene oxide) block copolymers or ω-hydroxypolystyrenes as the steric stabilizers. Different parameters such as the manner of addition of the reactants, the concentration, and length of the stabilizer were varied to tune the polyurethane particle size. When ω-OH polystyrenes of low molar mass ( $$\bar M_n $$ =2000–3000 g mol–1) were used as the reactive stabilizers of dispersion, polyurethane particles in a tunable size range of 0.2–5 µm with a narrow size distribution (span = 0.7) could be prepared.

The use of rigid organic microemulsions to fix liquid solutions for Mössbauer studies

Rigid organic microemulsions containing submicroscopic droplets of liquid solutions of tin(IV) chloride in methanol and in ethylene glycol were prepared. In those systems where the walls of the cavities in the microemulsion carried negative charges and the hydrophilic groups of the surfactants and cosurfactants had H-bonding ability, it was shown that the internal surface of the cavities in the microemulsion was covered by a solvent layer separating Mössbauer-active SnCl 4 from this surface. On the other hand, solvated SnCl 4 was bound through the H-bonded solvent cluster to this surface-bound solvent by H bonds, resulting in recoilless γ-ray resonance absorption (Mössbauer effect). Thus, the rigid organic dispersion medium of these microemulsions behaved as a carrier enhancing the Debye-Waller factor for the quasi-liquid phase of the system, resulting in Mössbauer spectra characteristic of SnCl 4 in the bulk solution.

M�ssbauer spectroscopy of liquid SnCl4 solutions trapped in a rigid microemulsion

A rigid microemulsion was prepared containing submicroscopic droplets of liquid aqueous tin tetrachloride solution. Recoillessγ-ray resonance absorption (the Mossbauer effect] was achieved in this system, indicating that the organic dispersion medium of the microemulsion behaved as a carrier, enhancing the Debye-Waller factor for the quasiliquid phase of the system. The Mossbauer spectra reflected the presence of two types of tin(IV) in the cavities of the microemulsion: SnCl4 species situated in the bulk solution and on the cavity wall, respectively.