Vol 65, No 1 (2023)

The rheological properties of the poly(vinyl alcohol)–water system under the magnetic field and in its absence are studied. It is found that application of the magnetic field leads to changes in the viscosity of the system and the morphology of supramolecular particles formed in solutions. The concentration dependence of the relative viscosity is described by a curve with a maximum.

This contribution is focused on the examination of adsorption/desorptiom isotherms for nitrogen at 77 K and benzene vapors at 293 K on various hypercrosslinked polystyrene (HP) resins. All isotherms for N2 are identical in their shapes and are characterized by a steep rise of the adsorption branch at low p/p0 followed by a less steep hoisting of the branch with increasing relative pressure. Adsorption isotherm for benzene demonstrates an ill-defined convex initial part followed by a significant rise in network loading with further increase in relative pressure. In the both cases we assume the rise in adsorption to reflect the relaxation of inner stresses with the simultaneous increase in the volume of networks. The distinction between the two types of isotherms is conditioned upon the fact that in the networks cooled down to 77 K stresses are stronger and the initial volume of the sample is more compressed. The amounts of nitrogen and benzene absorbed at relative pressure of 0.95 are the same order of magnitude, indicating similar swelling of HP in the both adsorbates. The adsorption behaviors of hypercrosslinked PIM-type polymers are governed by the same effects.

A series of novel anionic block copolymers, in which the neutral block is formed by 2-phenylethyl methacrylate (PEM) and the ionic block is prepared via statistical copolymerization of lithium 1-[3-(methacryloyloxy)-propylsulfonyl]-1-(trifluoromethanesulfonyl)imide (LiM) and methyl ether of poly(ethylene glycol) methacrylate (PEGM) have been synthesized. The effects of chemical structure, composition, and molecular mass of the blocks on ionic conductivity and thermal properties of the poly[PEM–block–(LiM–stat–PEGM)] block copolymers have been investigated. It has been found by means of small-angle X-ray scattering that the introduction of a small fraction of the lithium-containing units (~7 mol %) in the structure of neutral poly[PEM–block–PEGM] copolymer leads to microphase separation and ordering of the system. Combined small-angle X-ray scattering and atomic force microscopy data have evidenced the formation of lamellar structure with the interplanar distance of d ~ 28 nm.

The process of complex formation between polyethylenimine and copper cations in an aqueous solution, followed by isolation of copper nanoparticles, has been studied by means of ESR spectroscopy. It has been shown that in excess of the polymer in the solution the copper cation forms complex containing three nitrogen atoms in the coordination sphere, with distorted tetragonal geometry. The increase in copper concentration has led to the formation of the copper cation complex with water. Addition of the reducing agent NaBH4 to the studied solutions has led to the formation of copper nanoparticles accompanied by gradual disappearance of the ESR signal of Cu(II) and the appearance of the ESR signal typical of the mononuclear copper complexes with polyethylenimine.

Effect of the structure of synthetic polyacids on the formation and properties of their interpolymer complexes with sodium alginate is investigated. The hydrogels was shown to be predominantly formed via hydrogen bonds, with their type depending on the structure of polyacid and the amount of bound water. Study of the behavior of the hydrogels in water and phosphate-buffed saline with рН 7.2 demonstrates that the properties of the hydrogels are influenced by the ratio of components and the treatment temperature, in addition to the nature of polyacid. The possibility of using hydrogels as a basis for drug delivery systems is examined by the example of preparation lidocaine.

Structure formation during deformation of a mixture of melts of a thermoplastic polymer (polysulfone) and a liquid crystal polymer has been investigated by means of analytical scanning electron microscopy. Viscosity of the LC polymer at high shear rate has been significantly lower in comparison with the thermoplastic. The experiment has been performed at controlled volume flow under conditions of flow through a capillary at a high and low deformation rate. The principal result of the observations has been the statement of self-organization effect manifested as the phase separation and formation of the regions with the increased concentration of the LC polymer in the thermoplastic matrix. Such system has been an emulsion, and a conical converging flow has been formed at the transition from the wide cylinder of the capillary viscometer to a narrow capillary installed at its bottom. Such geometry of deformation has led to the appearance of a longitudinal flow with the formation of jets (fibers) in the extrudate bulk and the surface layer of the liquid crystal polymer. Effective viscosity of the mixture has been lowered in comparison with this of the thermoplastic, due to self-assembly of the LC polymer.

Laboratory and field stability tests for a composite based on low-density polyethylene with an organomineral biocidal additive to the effects of aqueous media have been carried out. As an organomineral additive, polyhexamethyleneguanidine hydrochloride (a high-molecular-weight nontoxic biocide used in antiseptic solutions) immobilized on an inorganic carrier (montmorillonite) was used to improve the quality of distribution of the organomineral additive in a thermoplastic polymer (without loss of the biocidal properties of polyguanidine) and to prevent polyguanidine from being washed out of the composite during operation. The composition and structure of the composite with an organomineral additive remain unchanged after exposure to distilled water and model seawater. Field tests of the composites in seawater at a depth of 1.5 m in a tropical climate revealed that there were no polyguanidine leaching from the material even after 21 months of exposure of the samples. The samples without an organomineral additive undergo insignificant photo-oxidative aging, whereas the molecular structure of the polymer in the composite with the additive is unchanged. Thus, the studied organomineral additive has a photostabilizing effect on polyethylene. When the samples are exposed to seawater, there is a slight decrease in the strength of the samples and an increase in the elastic modulus, which is associated with an increase in the degree of crystallinity of polyethylene during aging.