卷 65, 编号 2 (2023)

The thermodynamics of interaction between poly(perfluorosulfonic acid) Nafion and water is studied by isothermal sorption and microcalorimetry. The concentration dependences of energy and entropy parameters of mixing of Nafion aqueous solutions are determined. It is shown that the Gibbs energy and the enthalpy of mixing are negative while the entropy of mixing is positive over the entire range of solution compositions. The experimental water sorption isotherms and the concentration dependences of the enthalpy of dilution of aqueous solutions are analyzed in terms of the thermodynamic model allowing for pair nonvalence interactions in solution, nonequilibrium glassy structure of the polymer, and effects of the dissociation of ionic sulfo groups of Nafion. The calculated value of the Flory–Huggins parameter is 1.48, and the value of its enthalpy component is close to zero.

Issues related to the use of 2-hydroxyethyl methacrylate–glycidyl methacrylate copolymers as a polymer matrix for developing solid polymer electrolytes are considered. Effect of the composition of copolymers with varying ratio of oxygen atoms in hydroxyl, carbonyl, ether, and epoxy groups and the amount of the added lithium salt on the ionic conductivity of the solid polymer electrolytes is studied. The resulting polymer films exhibit a high ionic conductivity reaching up to 1.2 × 10‒4 to 1.2 × 10‒3 S/cm at 25 and 80°С, respectively.

Anisotropic magnetically active elastomers based on polydimethylsiloxane and magnetic particles of different chemical natures, shapes, and sizes have been synthesized. A comparative analysis of their mechanical properties (elastic modulus, strength, and elongation at break) has been performed depending on the mutual orientation of the internal structure, formed by magnetic filler particles during the synthesis of the composite in a magnetic field, and the direction of the external mechanical force applied to stretch the samples. The anisotropy of mechanical properties is most pronounced in composites based on anisometric particles, needle-like and plate-like. The highest values of anisotropy coefficient of elastic modulus are observed in the composite containing plate-like iron microparticles; for this composite, the ratio of the elastic moduli in the directions parallel and perpendicular to the internal structure reaches a value of five. The use of magnetic filler and its orientation by means of magnetic field is an effective method for creating polymer composites with anisotropy of mechanical properties.

The approach to the prediction of permeability of polymer membranes based on polyimides and polyamidoimides towards helium is described. According to the approach, the activation energy of helium penetration is expressed by a relationship involving the van der Waals volume of the repeat unit and a set of atomic parameters characterizing the contribution of each of the atoms and intermolecular interaction types into the value of activation energy. The contributions of the imide cycles, type of the connection (meta-, para-, or ortho-), and of the CF3, CH3, CO, Cl, F, and SO2 polar groups have been accounted for. Repeated solution of the redundant set of equations obtained on the basis of the proposed relationship has afforded the parameters giving the correspondence of the calculated values and the experimental data on the membranes permeability with correlation coefficient 0.965. Hence, the possibility to search for the structures of polyimides and polyamidoimides with the target permeability without laborious and expensive experiments has been demonstrated.

The changes in conformational structure of polyampholyte polypeptides adsorbed at the surface of a charged spherical gold nanoparticles polarized in a uniform external electric field have been studied by means of molecular dynamics. Distributions of the mean unidimensional density of the polypeptide atoms along the axis of the nanoparticle polarization and radial distributions of the mean density of the atoms of polypeptides adsorbed at the nanoparticle surface have been computed. When the surface charge of the charged nanoparticle in one of the near-pole regions are compensated by the charges induced at the nanoparticle by the external electric field, the polyampholyte skirt non-symmetric with respect to the equator has been formed. Compaction of the macromolecular layer at one of the near-pole regions has occurred, whereas the polyampholyte skirt at the other near-pole regions has been swollen with the formation of the macromolecule chain loops, their length depending on the spacing between the charged units in the macromolecule. When the total charge of the nanoparticle in the uniform electrical field is low, the polyampholyte skirt stretched along the polarization has been formed at the nanoparticle surface. At low strength of the external uniform electric field, the charged nanoparticle has been uniformly wrapped by a macromolecular skirt consisting of three layers: two oppositely charged ones and a neutral layer between them.