The colloid-chemical properties of water-soluble and poorly soluble poly(ethylene oxide) and poly(propylene oxide) block copolymers (pluronics), as well as the rheological properties of interfacial adsorption layers (IALs) formed by them and the polymer generated during polymerization initiation on the particle surface, were studied. The temperature, surfactant concentration, and polymer effects on the effective elastic modulus, determined during the lateral deformation of IALs, were evaluated. The strongest interfacial layers are formed by the poorly water-soluble pluronic, which contains a hydrophilic polyoxyethylene block surrounded by two hydrophobic polyoxypropylene blocks. The high strength of the interfacial adsorption layer on the particle surface affords polymer suspensions with high (up to 33
The colloidal-chemical properties of oxyethylated polypropylene glycols (pluronics), soluble and slightly soluble in water and containing a hydrophobic polypropylene glycol block with the same length but with different degrees of oxyethylation, were analyzed. It was determined that both pluronics are characterized by high surfactant properties, making it possible to use them as surfactants in heterophase polymerization processes. The observed differences in the kinetic specific features of the polymerization of styrene and methyl methacrylate (average particle diameter and polymerization rate, the character of the monomer conversion—time curves) allowed us to infer that the formation of the polymer-monomer particles occurs by different mechanisms. The obtained results showed that these surfactants are promising for the synthesis of polymer suspensions with a narrow particle size distribution and an average diameter in the range from 0.09 to 1.7 µm.
The paper shows the similarity of kinetic regularities of vinyl monomers polymerization in the presence of Laprol 6003, regardless of the degree of solubility of the monomers in water. It is assumed that this feature of polymerization is due to the same mechanism of formation of polymer-monomer particles (PMP) – from monomer microdroplets. The interfacial adsorption layer of PMPs, the main site of polymerization, is formed from a surfactant adsorbed from the bulk of the monomer phase and a polymer formed in the adsorption layer upon initiation of polymerization. The formation of complex structures in the interfacial adsorption layer of particles, the incompatibility of the surfactant and the resulting polymer, and high viscosity cause the formation of a strong interfacial layer that ensures the stability of polymer suspensions from the early stages of polymerization.
The colloid-chemical properties of organosilicon surfactants with different solubility in water were studied. The behavior of organosilicon surfactants of various structures in model systems - Langmuir films at the water-air interface has been studied. The results obtained showed that high stability of polymer suspensions is observed only in the presence of insoluble in water organosilicon surfactants.
The colloidal chemical properties of triple block copolymers of polypropylene oxide and polyethylene oxide (pluronics of various structures) were studied in comparison. All of them are shown to be surfactants but differ in interfacial tension, surface activity, surface area occupied in the adsorption layer, and adsorption layer thickness. The kinetic regularities of polymerization of styrene and methyl methacrylate were studied. The particle diameters and their size distribution were determined. Distinctions in the kinetic regularities of polymerization are shown: the shape of the conversion—time curves (for the duration of the initial and stationary stages of polymerization) and the dependences of the diameter on the surfactant concentration and monomer to water volume ratio. In the presence of the water-insoluble pluronics, the mechanism of formation of polymer—monomer particles and interfacial layer on the surface differs from that when using water-soluble surfactants, which makes it possible to distinguish these processes into an independent type of heterophase polymerization.
The possible reasons for the occurrence of emulsion polymerization of a monomer simultaneously with suspension polymerization, namely the formation of polymer particles from a highly dispersed fraction of monomer droplets in the initial emulsion and associates of high molecular weight surfactants, are considered. Data on colloidal solubility of monomer in surfactant associates and data on determination of hydrodynamic radii of high molecular weight surfactant associates are presented. The results obtained can be the basis for the choice of surfactants in suspension polymerization, which ensure the minimum contribution of the highly dispersed fraction of monomer droplets to the formation of polymer-monomer particles.
The possible reasons for the occurrence of emulsion polymerization of a monomer simultaneously with suspension polymerization, namely the formation of polymer particles from a highly dispersed fraction of monomer droplets in the initial emulsion and associates of high molecular weight surfactants, are considered. Data on colloidal solubility of monomer in surfactant associates and data on determination of hydrodynamic radii of high molecular weight surfactant associates are presented. The results obtained can be the basis for the choice of surfactants in suspension polymerization, which ensure the minimum contribution of the highly dispersed fraction of monomer droplets to the formation of polymer-monomer particles.
The current article describes the impact of ammonium nitrate granule structure on detonation characteristics of industrially used explosives. It was found that combined treatment with application of ultrasonication along with surface active agents significantly increases the content of nano-micro dispersed structural elements in ammonium nitrate granules when done in the presence of oil/water emulsion. It was shown that the exposure to pore forming emulsion and combined physicochemical treatment (magnetic pulse and ultrasonication) increased the blast destructive activity of charge together with reduction of environmental pollution due to improved detonation density.
A set of rheological experiments is performed for interphase adsorption layers at a water/butyl methacrylate interface formed by high molecular weight surfactants (HMWSs) (polyvinyl alcohol with various acetylated groups (PVA) and copolymer 2-acrylamido-2-methylpropanesulfonic acid with methyl methacrylate (AMPSA-MMA) having different contents of MMA links). It is shown there is an increase in the content of acetylated groups and MMA units in the studied HMWSs produces structures at the interface that differ in higher values of the viscosity and elastic modulus of the adsorption layer. The aggregate stability of dispersion during the suspension polymerization of acrylic monomers grows along with the content of hydrophobic units in the HMWS polymer chain.
The dispersion composition of polymer suspensions and molecular weights of polymers obtained by suspension polymerization of MMA in the presence of polymer surfactants – methylmethacrylate and methacrylic acid copolymers – were studied. It is shown that a highly dispersed fraction of particles with diameters of 0.02–2.0 µm and a fraction of particles with large diameters (up to 1000 µm) are always present in the polymer suspension. After fractionation of polymer suspensions 3 fractions of particles with different diameters were obtained. For each particle fraction the molecular masses of polymers were determined by viscometry. A significant difference in the values of the molecular masses of polymers obtained as particles of small and large diameters – 105 and 106 Da, respectively – is shown. The presence of a highly dispersed fraction of particles in which a polymer of high molecular weight is formed has a noticeable effect on the average molecular weight of the polymer. In particles of small diameter polymerization takes place according to a mechanism close to the emulsion, due to the fact that the volume of such particles contains a small amount of radicals. The high rate of polymerization leads to the formation of a polymer of high molecular weight, the appearance of a gel effect and a decrease in the termination constant. In most particles, polymerization proceeds by a mechanism close to the solution polymerization, and polymers of low molecular weight are formed. This makes it possible to synthesize polymers of a given molecular weight in drops of certain dispersity.
The effect of the composition and structure of oligodimethylsiloxanes containing carboxy- and amino-functional substituents at the silicon atom on their colloidal-chemical properties was studied. It was established that their colloidal-chemical properties are affected not only by the nature and concentration of functional groups, but also by the molecular weight of the organosilicon compound.
The behavior of organosilicon surfactants of different structure in model systems—Langmuir films—at the water/air interface is studied. It is shown that, under the compression of Langmuir films, the conformational states of surfactants of different structure are different. The obtained data make it possible to explain a high stability of polymer suspensions synthesized in the presence of organosilicon surfactants.
The results of the study of various modification methods of polymer microspheres for their use in immunochemical reactions as bioligand carriers are reported. Ion etching and electron microscopy were used to show that the copolymer microspheres have a porous structure non-uniform in density. The Maillard reaction was used for the first time in the modification of copolymer microspheres by dextrans of different molecular weight as a simplest way of covalent immobilization of saccharides on their surface. The physicochemical properties of polystyrene-divinylbenzene and polyglycidyl methacrylate-ethylene glycol dimethacrylate microspheres modified with diamines and dextrans were determined for the first time. The conditions under which the bioligand (diphtheria toxoid) immobilized on their surface retained the native conformation and the diagnostics obtained on their basis have high sensitivity were revealed.
Theoretically substantiated and experimentally determined viscosity and adhesive properties of the experimental compositions of the liquid formulation with plant extracts of Eucalyptus (evkalimin) and Echinacea purpurea (estifan). It proved that are designed mucoadhesive pharmaceutical compositions that might provide a sustained action on the surface of the oral mucosa.
Adsorption properties of γ-Al2O3 modified with Co (5 and 10 wt %) and Co (5 wt %) species are investigated by dynamic adsorption. N-hexane, n-heptane, n-octane, benzene, toluene, ethylbenzene, chloroform, and diethyl ether were used as test adsorbates. Adsorption isotherms were measured, and isosteric adsorption heats were calculated for the indicated sorbates. It was shown that the adsorption isotherms of all the adsorbates and at all the temperatures of measurements on γ-Al2O3 modified with Co (5 wt %) and CoO (5 wt %) nanoparticles located above that recorded for the initial γ-Al2O3 sample. It was established that the surface of modified γ-Al2O3 possessed mainly electron-accepting properties. The 5% Со/γ-Al2O3 and 5% СоO/γ-Al2O3 nanocomposites exhibited the greatest adsorption capacity relative to aromatic hydrocarbons.
The composition and technology for the preparation of a combined water solution of hydrophobic plant extracts, eucalymine and estifan are developed. The concentration of surfactants (Tween 20 and 80) and soya lecithin that is optimal for obtaining stable miniemulsion systems is determined. The sizes and zeta potential of the obtained dispersed nanoscale particles are established.
This paper presents the results of studies of seed copolymerization of glycidyl methacrylate with ethylene glycol poly(glycidyl methacrylate) on seed particles in order to obtain partially crosslinked polymer microspheres with a diameter of about 3.5 microns for use in immunochemical reactions, as carriers of bioligands. The physico-chemical properties of polymeric microspheres obtained under different conditions were studied by the following methods: the diameters of the particles - by electron scanning and light microscopy; the wetting angle - bу the method of "lying droplets"; the sedimentation velocity - by the macromethod in a capillary tube by the movement of the (polymer slurry)/water phase boundary (buffer solution); the zeta-potential - by dynamic light scattering. Having studied the physical-chemical properties of all polymer slurries we concluded that the optimal particles to create on the basis of their diagnostic test systems with high sensitivity working on the principle of latex agglutination reaction are poly(glycidyl methacrylate) particles with equal percentage of glycidyl methacrylate and ethylene glycol dimethacrylate aminated with hexamethylendiamine in the environment of n-propanol, because they have a sufficient number of amino groups and do not lose their sedimentation properties after all stages of the synthesis.