Vol 65, No 5 (2023)

The structure and rheological properties of aqueous solutions of the anionic surfactant potassium oleate and the water-soluble monomer acrylamide before and after radical polymerization have been studied. In the absence of monomer and in the presence of a low-molecular-weight salt, potassium oleate forms a network of long entangled cylindrical (wormlike) micelles. The addition of the monomer does not lead to a change in their cylindrical shape and radius, but it promotes the transformation of branched micelles into linear ones. The structure of surfactant aggregates changes significantly after polymerization: according to neutron scattering data, it becomes bicontinuous and its local geometry becomes lamellar. The coexistence of such a structure with polyacrylamide macromolecules in a semidilute solution leads to a significant synergistic increase in viscosity and elastic modulus.

This work is aimed at the preparation of complexes of chitosan and hydrophobically modified (HM) chitosan with an anionic surfactant sodium dodecylbenzene sulfonate (SDBS), and at the study of the virucidal activity of the complexes and their components against SARS-CoV-2. It is shown that the introduction of a sufficient amount (4 mol%) of hydrophobic n-dodecyl side groups provides the activity of HM chitosan against SARS-CoV-2 at moderate concentrations, at which unmodified chitosan and chitosan containing a lower amount of hydrophobic groups do not show any activity. Complexes of HM chitosan with SDBS are prepared, which is proven by fluorescence spectroscopy and isothermal titration calorimetry. It is discovered that HM chitosan/SDBS complex is more active than the polymer without surfactant, and an increase of the amount of hydrophobic groups enhances the activity

Using two samples of chitosan (D-glucan) with viscosity-average molecular mass 40 × 103 and 200 × 103 as the example, the influence of diastereomer form (L- and D-) of ascorbic acid on the energetics of formation, structure, and supramolecular ordering of hetero- (D‒L) and homochiral (D‒D) polymer–acid salt complexes has been studied. It has been found that heat effect during the interaction of chitosan with L-ascorbic acid in aqueous medium and degree of protonation of the (D‒L)-salts are lower in comparison with D-isomer of the acid. The homochiral (D‒D)-salts, in contrast to the heterochiral (D‒L)-salts, have exhibited lower amount of crystallization water, high degree of crystallinity, and denser supramolecular structure with high level of inter- and intramolecular contacts.

The effect of vulcanization system on the properties of polymer-elastomer composite materials based on nitrile-butadiene rubber and ultrahigh molecular weight polyethylene is studied. An analysis of the rheometric and vulcanization characteristics of rubber compounds shows that, in the case of combined sulfur-peroxide vulcanization system, the crosslinking density of vulcanizates increases considerably. The study of the elastic and strength behavior and dynamic mechanical properties of the vulcanizates demonstrates that the sulfur-peroxide vulcanization system provides the best parameters, in particular at low temperatures. An examination of elastic and hysteresis properties of the samples before and after vulcanization, which are measured under dynamic loading in a wide frequency and strain range, allows one to describe the features of physicochemical interactions in polymer-elastomer materials depending on the used vulcanization system. The supramolecular structure of the vulcanizates is visualized by scanning electron microscopy, and chemical interaction between macromolecules of nitrile-butadiene rubber and ultrahigh molecular weight polyethylene occurring during peroxide vulcanization is proved by IR spectroscopy.

Nanocomposites of low-density polyethylene (LDPE) with a nanocarbon nanofiller, reduced graphene oxide (RGO) of different composition, have been obtained under conditions of high-temperature shear deformations in a rotary disperser. Structure and properties of the obtained nanocomposites have been studied using a wide range of physico-chemical methods of analysis, including laser diffraction, scanning electron microscopy, and measurement of mechanical and electrical parameters. The influence of the components ratio in the compositions on the characteristics of the resulting materials has been demonstrated.

A laboratory procedure has been suggested for determining the concentration of carboxyl groups at the surface of polystyrene microspheres at the latex concentration of a few hundredths of weight percentage (the COOH groups concentration below 4 × 10−4 mol/L). The procedure is based on conductometric and potentiometric titration. The influence of polymer particles concentration in the system, ionic strength of the solution, titration duration, and the system inertness on the obtained values of the carboxyl groups concentration and the determination accuracy have been investigated.