Vol 65, No 4 (2023)

Protonated diallylammonium polymers are special among cationic polyelectrolytes, due to a series of properties including high antimicrobial activity, for example, towards Mycobacterium tuberculosis. The polymers samples should be characterized properly for their practical application. In this study, protonated secondary polydiallylamines based on diallylammonium trifluoroacetate have been synthesized via radical reversible addition−fragmentation chain-transfer polymerization in the presence of 2-[(ethoxycarbonothioyl)sulfanyl]acetic acid. The NMR spectroscopy data have shown that the macromolecules contain the dithiocarbonyl terminal groups enhancing the polymer solubility in nonaqueous media, for instance, in methanol. The obtained polymers have been investigated by means of hydrodynamics and dynamic light scattering methods; molecular mass and hydrodynamic parameters of the macromolecules have been determined. Comparison of the polymers with similar ones synthesized via conventional radical polymerization and bearing terminal vinyl groups has revealed the independence of their hydrodynamic properties in 1.0 mol/L NaCl on the synthesis method and the terminal groups structure at М > 8 × 103, thus allowing the application of the scaling relationships for the diallylammonium polymers to determine the molecular mass, irrespectively on the preparation methods.

Ionic liquids, salts with melting temperature below 100°C, have continuously attracted research interest. Introduction of ionic liquids in a polymer matrix affords polymer electrolytes exhibiting extremely high electroconductivity and electrochemical stability, membranes on their basis possessing good mechanical properties. Diversity of the polymers/copolymers suitable as the matrix as well as practically unlimited variety of ionic liquids (obtained via variation of the anion-cation composition and additional modification of the ions chemical structure) have afforded the polymer electrolytes with a wide range of the physico-chemical properties. In this study, the attention has been primarily focused on the results published over the recent decades and related to investigation of electrolytes for electrochemical devices, in which the membranes based on polybenzimidazole (meta-PBI), the poly(vinylidene fluoride-со-hexafluoropropylene) (PVdF-HFP) copolymer, and ammonium or imidazolium ionic liquids have been used. Various types of polymer electrolytes differing in the composition and the application range have been considered in this study: polymer + ionic liquid, polymer + ionic liquid + acid, and polymer + ionic liquid + lithium/sodium salt. Moreover, the influence of the fillers, introduced in the above-said polymer electrolytes to improve the properties and resolve the issue of the ionic liquid retention in the membrane, has been discussed. This report presents vast data sets (tables) on the electroconductivity and thermal stability of more than 100 polymer electrolytes, which are demanded by the broad journal audience.

The influence of different types of deformation of the metal matrix on mechanical behavior of the amorphous PET film upon its transverse compression in the ductile metal matrix has been investigated. Three deformation modes have been probed. In the first case, a disc-shaped polymer specimen has been put between two 5 mm thick discs of the lead–tin alloy and squeezed in the press. In the second and the third cases, planar elongation has been performed in the so called “dead channel”, i.e., the channel with fixed side walls, the film being elongated due to decrease in the width or thickness, respectively. The plots of true yield stress at different draw ratios have formed a common master curve. At high total draw ratio Λ, the true yield stresses have been close for the considered three types of drawing in the metal. At the draw ratio Λ > 2.6, the neck has not appeared, and the specimen has been deformed uniformly. When the film in the channel is elongated due to the decrease in thickness at constant width, the specimen width has been mainly decreased during subsequent elongation in the testing machine. When the film in the channel is elongated due to the decrease in width at constant thickness, further elongation has mainly led to the decrease in the specimen thickness. The true stress Σ has been expressed as Σ = Σ0 + KΛ3, with K being a constant. Deformation of the polymer in the channel occurred with the formation of shear bands. At the preliminary draw ratio Λ = 1.82, the bands have been oriented at the angle 21.5° with respect to the stretching axis. The planar elongation has led to abnormally strong deformation softening of the polymer. The drawing has been accompanied by an increase in the elasticity modulus of the polymer. The obtained results have suggested that the macromolecules orientation is the main reason for strain hardening of the polymer.

Reactor polymer compositions (RPCs) based on UHMWPE with Mw = 1000 kg mol–1 and low molecular weight HDPE (LMWPE) were studied. Two series of UHMWPE compositions were used to determine the influence of the molecular weight and properties of the LMWPE fraction on the morpho-logy, mechanical and rheological properties of UHMWPE/LMWPE. Сompositions, including from 10 to 80 wt % UHMWPE with Mw = 160 kg mol–1 (PE-160) were obtained in a two-stage process of ethylene polymerization with a metallocene catalyst. They differed in the order of introduction of PE-160 into UHMWPE (PE-160/UHMWPE and UHMWPE/PE-160). Compositions of UHMWPE and LMWPE with Mw = 48 kg mol–1 (PE-48/UHMWPE) with PE-48 content from 6 to 30 wt % were synthesized in a single-stage polymerization of ethylene in the presence of a tandem catalyst. A comparison of the shape and size of particles of nascent polymer products was made using the SEM method. The morphology, tensile, dynamic mechanical and rheological properties of RPC have been studied depending on the method of their preparation, the content of the low molecular weight fraction, its molecular weight and physical and mechanical properties. An increase in the proportion of PE-160 and PE-48 in PE-160/UHMWPE and PE‑48/UHMWPE leads to an increase in RPC crystallinity, tensile modulus and dynamic mechanical modulus with significant deviations from the additivity rule.

The effect of thermal oxidation on the crystalline phase of polypropylene in composites with single-walled carbon nanotubes has been studied. The composites are synthesized in propylene bulk using a homogeneous catalytic system rac-Me2Si(2-Me-4PhInd)2ZrCl2, activated by methylaluminoxane. The effect of thermal oxidation on thermophysical characteristics (the heat of melting and the melting temperature) measured by DSC and changes occurring in the polymer investigated by IR spectroscopy is studied. Changes in the structure of PP during thermo-oxidative degradation are studied by DSC at 140 and 170°С, that is, before and after melting of the samples. It is shown that the oxidized PP in the composites possesses a higher degree of crystallinity and a more perfect structure than the pure PP. At 170°С the effect of thermo-oxidative stabilization is observed only at low filling degrees (up to 3 wt %), in agreement with the TGA data. An analysis of IR spectra demonstrates that the presence of nanotubes in PP‑based composites during oxidation slows down the formation of oxygen-containing groups in the polymer. The conclusion is made that carbon nanotubes inhibit the thermal oxidation of polypropylene in the composites.

A theoretical model describing the self-assembly in dilute solutions of amphiphilic macromolecules containing the backbone built of the solvophilic units (the P groups) and the solvophobic side chains (the H groups) possessing orientational mobility relative to the backbone units has been elaborated. In the framework of strong segregation limit (The size of the insoluble regions of the formed micelles is on the order of the hydrophobic side chains), state diagrams of the solution have been calculated with and without accounting for the orientational entropy contribution of the side groups to the total free energy of the solution at different thermodynamic qualities of solvent for the macromolecules and the grafting density of the H groups; the regions of stability of spherical and cylindrical micelles as well as planar bilayers (vesicles) have been revealed. It has been found that the contribution of the orientational entropy significantly affects the view of the state diagrams. In the case of considering the orientational mobility, the conditions of the cylindrical micelle stability are very sensitive to the change in the grafting density of the side groups. This sensitivity can be the reason why the formation of long cylindrical (wormlike) micelles is not observed in experiments and computer simulations. As earlier demonstrated at a qualitative level, the orientational mobility of the side groups can lead to the emergence of the orientation-induced attraction between the polymer micelles (A. I. Buglakov, D. E. Larin, and V. V. Vasilevskaya, Polymer 232, 124160 (2021)). In this study, exact analytical calculations of the energy of orientation-induced attraction for the case of the interaction between two planar bilayer micelles has been performed. At distances being of the order of the size of the side H group, the orientation-induced attraction forces are much stronger than the van der Waals forces and, hence, the orientation-induced attraction can be decisive in the formation of large aggregates observed in experiments.