Copolymers based on vinylidene fluoride are potential materials for ferroelectric memory elements. The trend in studies showing that a decrease in the degree of crystallinity can lead to an unexpected increase in the electric breakdown field is noted. An analysis of the literature data reveals that in fluorine-containing ferroelectric polymers, when using a bipolar triangular field, the hysteresis loop has an unclosed shape, with each subsequent loop being accompanied by a decrease in the dielectric response. In this work, the effect of the structure of self-polarized films of copolymers of vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene on breakdown processes was studied. The structure of the polymer films was monitored using infrared spectroscopy (IR) and X-ray diffraction. Kelvin probe force microscopy (KPFM) was applied to characterize the local electrical properties of the polymers. For the films of the first copolymer, which crystallize in the polar β-phase, asymmetry in the dielectric response was observed at fields greater than the coercive field. For the films of the copolymers of vinylidene fluoride with hexafluoropropylene, which crystallize predominantly in the nonpolar α-phase, polarization switching processes have also been observed, but at lower electric fields. The noted phenomena will help to identify the influence of the structure of ferroelectric polymers on their electrical properties.

This paper presents data on the macroscopic polarization of copolymer films of vinylidene fluoride with tetrafluoroethylene obtained with a modified apparatus assembled according to the Sawyer–Tower Circuit. The kinetics of the polarization process were analyzed taking into consideration the contributions of both bound and quasi-free (impurity) charges. It was shown that an “abnormal” decrease in conductivity was observed in fields near the coercive fields. This could be associated with the appearance of deep traps of the impurity charge carriers formed by the polar planes of β-phase crystals. The conductivity data obtained from the charge and current responses differed. It was concluded that chain segments contributing to polarization with sufficiently low fields were present in the amorphous phase. A comparison showed that the average size of β-phase crystals (crystals of X-ray diffraction reflection width) was almost one order of magnitude lower than the domain size obtained using piezoresponse force microscopy (PFM). The analysis of the fast-stage dielectric response before and after polarization indicated that as the external polarizing field increased in the ferroelectric polymer chains, conformational transitions occurred according to the T3GT3G− → (-TT-)n и TGTG → (-TT-)n types. This was accompanied by an increase in the effective dipole moment in the amorphous phase chains. The analysis of the IR spectroscopy data obtained in transmission and ATR modes revealed a difference in the conformational states of the chains in the core and surface parts of the film.

The synthesis of neodymium carboxylates (neodecanoate and 3,5,5-trimethylhexanoate) and their application in developing Nd-loaded liquid organic scintillators are discussed. Neodymium carboxylates were obtained through a one-step synthesis (for 3,5,5-trimethylhexanoate) and a two-step synthesis (for neodecanoate). The composition of the synthesized compounds was confirmed using IR spectroscopy, elemental analysis, and MALDI-TOF MS. To incorporate neodymium carboxylates into a liquid organic scintillator, an additional solvent, tributylphosphate, was proposed. It was demonstrated that the scintillator’s light output, when using this solvent, is more than 60

Three types of coatings (contact-based, release-based, and combined coatings with both contact-based and release-based actions) were prepared and tested for the ability to inactivate SARS-CoV-2. In these coatings, quaternary ammonium surfactants were used as active agents since quaternary ammonium compounds are some of the most commonly used disinfectants. To provide contact-based action, the glass and silicon surfaces with covalently attached quaternary ammonium cationic surfactant were prepared using a dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride modifier. Surface modification was confirmed by attenuated total reflection infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and contact angle measurements. The grafting density of the modifier was estimated by XPS and elemental analysis. To provide release-based action, the widely used quaternary ammonium cationic disinfectant, benzalkonium chloride (BAC), and a newly synthesized cationic gemini surfactant, C18-4-C18, were bound non-covalently to the surface either through hydrophobic or electrostatic interactions. Virus titration revealed that the surfaces with combined contact-based and release-based action and the surfaces with only release-based action completely inactivate SARS-CoV-2. Coatings containing only covalently bound disinfectant are much less effective; they only provide up to 1.25 log10 reduction in the virus titer, probably because of the low disinfectant content in the surface monolayer. No pronounced differences in the activity between the flat and structured surfaces were observed for any of the coatings under study. Comparative studies of free and electrostatically bound disinfectants show that binding to the surface of nanoparticles diminishes the activity. These data indicate that SARS-CoV-2 is more sensitive to the free disinfectants.

Bio-based eco-friendly cellulose nanocrystals (CNCs) gain an increasing interest for diverse applications. We report the results of an investigation of hydrogels spontaneously formed by the self-assembly of carboxylated CNCs in the presence of CaCl2 using several complementary techniques: rheometry, isothermal titration calorimetry, FTIR-spectroscopy, cryo-electron microscopy, cryo-electron tomography, and polarized optical microscopy. Increasing CaCl2 concentration was shown to induce a strong increase in the storage modulus of CNC hydrogels accompanied by the growth of CNC aggregates included in the network. Comparison of the rheological data at the same ionic strength provided by NaCl and CaCl2 shows much higher dynamic moduli in the presence of CaCl2, which implies that calcium cations not only screen the repulsion between similarly charged nanocrystals favoring their self-assembly, but also crosslink the polyanionic nanocrystals. Crosslinking is endothermic and driven by increasing entropy, which is most likely due to the release of water molecules surrounding the interacting COO− and Ca2+ ions. The hydrogels can be easily destroyed by increasing the shear rate because of the alignment of rodlike nanocrystals along the direction of flow and then quickly recover up to 90% of their viscosity in 15 s, when the shear rate is decreased.

In this study, a combined morphological and scaling analysis of brushes synthesized by the "grafting-through" method was performed, and the possibility of regulation of the thickness was revealed on an example of polyacrylamide brushes. The chemical composition of the surface in the proposed three-step approach was analyzed by photoelectron and infrared spectroscopy. It was shown that the thickness of the dried brush can be tuned in a controlled manner by varying the polymerization temperature. The scaling dependence of the thickness of the dried brushes d on the length of the polymer d similar to L-v was obtained by comparing reflectometry and dynamic light scattering data. The value of the exponent v = 0.82 corresponds to a rather high grafting density, exceeding the density of mushroom-like (nu similar to 1/3) brushes and approaching the value for stretched polymer brushes (nu similar to 1). A 10-fold increase in the polymer molecular weight leads to a slight decrease in grafting density by a factor of 2, which suggests that the "grafting-through" approach allows obtaining brushes with a high grafting density independently of attached polymer chain length. Herein, the possibility of attachment of uniform polymer brush on large substrates with this approach was demonstrated, which means the scalability of the "grafting-through" technique. The considered approach opens up a simple way for surface modification with polymer nanolayers of controlled thickness.

An unusual neutral dinuclear palladium(II) complex with two head-to-head orientated μ-P,S-bridging ligands was obtained by the reaction of Pd(MeCN)2 Cl2 with (1R,5R)-3-(4-phenylthiobutoxy)-2,4-diphenyl-2,4-diaza-3-phospha-bicyclo[3.4.0]nonane. The dimeric structure of the complex in the solid state and in solution was thoroughly confirmed using appropriate analytical techniques: single crystal X-ray diffraction analysis, HRMS, FTIR and NMR spectroscopy.

Metal-loaded liquid organic scintillators (MeLS) are discussed from the point of view of light yield at high metal loading (Gd, Nd, Zr, In). It is shown that, when metal β -diketonates are introduced into the scintillator, its light yield is always lower than when carboxylates are used, which is explained by the structural difference between these complexes. The nature of the metal in some cases (Nd) also affects the light attenuation length and, consequently, the MeLS light yield. The composition of the solvent (the fraction of aromatics in the main solvent) and the degree of purification of the introduced metal complex also have a significant effect on the light yield.

The values of the surface potentials of two sides of films of polyvinylidene fluoride, and its copolymers with tetrafluoroethylene and hexafluoropropylene, were measured by the Kelvin probe method. The microstructures of the chains in the surfaces on these sides were evaluated by ATR IR spectroscopy. It was found that the observed surface potentials differed in the studied films. Simultaneously, it was observed from the IR spectroscopy data that the microstructures of the chains on both sides of the films also differed. It is concluded that the formation of the surface potential in (self-polarized) ferroelectric polymers is controlled by the microstructure of the surface layer. The reasons for the formation of a different microstructure on both sides of the films are suggested on the basis of the general regularities of structure formation in flexible-chain crystallizing polymers.

This paper is devoted to the study of the structure and thermomechanical properties of PVDF-based ferroelectric polymer film. Transparent electrically conductive ITO coatings are applied to both sides of such a film. In this case, such material acquires additional functional properties due to piezoelectric and pyroelectric effects, forming, in fact, a full-fledged flexible transparent device, which, for example, will emit a sound when an acoustic signal is applied, and under various external influences can generate an electrical signal. The use of such structures is associated with the influence of various external influences on them: thermomechanical loads associated with mechanical deformations and temperature effects during operation, or when applying conductive layers to the film. The article presents structure investigation and its change during high-temperature annealing using IR spectroscopy and comparative results of testing a PVDF film before and after deposition of ITO layers for uniaxial stretching, its dynamic mechanical analysis, DSC, as well as measurements of the transparency and piezoelectric properties of such structure. It is shown that the temperature-time mode of deposition of ITO layers has little effect on the thermal and mechanical properties of PVDF films, taking into account their work in the elastic region, slightly reducing the piezoelectric properties. At the same time, the possibility of chemical interactions at the polymer–ITO interface is shown.

The work was devoted to increasing the solubility of the anthelmintic agent niclosamide (NS). Methods for increasing the solubility of NS were described. Alternative methods to obtaining drugs with NS solubility increased 2 – 12 times were proposed. The cytotoxic effect of the various forms of NS was tested on HeLa tumor cells. It was found that a nanosuspension containing 6.6% NS showed the highest cytotoxic activity. The initial NS substance exhibited the minimum cytotoxic effect on HeLa cells as compared to a microemulsion, microcapsules, a solid dispersion, and a mixed NS:PVP solid dispersion (1:10 ratio). The cytotoxic effect of all dosage forms grew and did not depend on the NS concentration in the studied dosage forms if the incubation period of the tumor cells increased from 24 to 48 h.

Alginate hydrogels with embedded rigid percolating network of halloysite clay nanotubes were evaluated as a novel ink for 3D printing. Hydrophilic alginate macromolecules adsorbing on halloysite stabilize the network of the nanotubes and form their own network of interlaced polymer chains. The effect of halloysite content on the structure and properties of the hydrogels was studied by rheometry, thermogravimetric analysis, FTIR-spectroscopy, dynamic light scattering, transmission electron microscopy, and 3D cryo-electron microscopy. Hydrogels demonstrate a very pronounced shear-thinning at extrusion and rather quick viscosity recovery after extrusion assigned to rapid rearrangement of the network structure promoted by mobile alginate chains. Even at low volume fractions (up to 0.054) the nanotubes reinforce the hydrogel increasing its storage modulus up to 650 Pa and inducing the appearance of yield stress. These properties make the alginate/halloysite hydrogels promising for the application in 3D printing for fabrication of green and sustainable nanocomposite materials made from natural components.

Thermodynamic functions of crystalline and gaseous niobium chlorides in lower state of oxidation are presented. The thermodynamic properties of solid niobium chlorides including their clusters Nb3Cl8 (NbCl2.67) and Nb6Cl14 (NbCl2.33) in the temperature range from 298 to 1300 K were calculated using experimental low temperature isobaric heat capacity measurements, thermogravimetric and tensimetric data on the process of their thermal decomposition and mass-spectrometric determination of vapor phase composition during this process.The thermodynamic properties of gaseous lower niobium chlorides in the temperature range 298-2000 K were calculated using vibration frequencies of these molecules. The latter were obtained using suggested molecular structures by a method involving the application of the force constants estimated on the basis of vibration frequencies of vapors of titanium, zirconium and vanadium tetrachlorides in terms of modified valence force field.The vibration frequencies were used to calculate the thermodynamic functions of gaseous niobium lower chlorides in terms of the rigid rotator-harmonic oscillator approximation.The obtained thermodynamic data allowed us to calculate the composition of the vapor phase in the system Nb=NbCl5 (vapor) in the temperature range from 700 to 2000 K for pressures 10−6 and 1 atm. The mechanism of thermal decomposition of niobium cluster Nb6Cl14 (NbCl2.33) was determined under pressure of 1 atm and in vacuum.

The work presents the synthesis and characterization of fluorinated cyclophosphazenes, which are readily soluble in supercritical CO2 and can be used as textile finishing chemicals in a supercritical CO2 deposition process. The reaction of hexachlorocyclophosphazene with sodium alcoholate of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol was performed. The reaction product analysis suggested that all parent hexachlorocyclophosphazene molecules participated in the reaction, 4- and 5-substituted fluorinated cyclophosphazene molecules comprised most of the reaction product. Cloud point measurements confirmed that the product is soluble in supercritical CO2 at moderate conditions. Fluorinated cyclophosphazene coating was deposited from solutions in supercritical CO2 onto cotton textile. Scanning electron microscopy revealed that the coating is deposited uniformly. The textile after treatment was hydrophobic with an initial contact angle of 106 ± 8 degrees. The obtained fluorinated cyclophosphazenes can be considered as building blocks for the further development of phosphazenes that are soluble in sc CO2 and can be used as hydrophobic finishing chemicals with improved properties.

General problems of structural changes which occur at storage of two-phase crystalline polymers with a metastable structure at room conditions are considered on the example of a vinylidene fluoride - hexafluoropropylene copolymer. The physical aging occurs in flexible-chain crystalline polymers (polyethylene, fluoropolymers under consideration, etc.), where, due to low glass transition temperatures, the liquid-like dynamics of amorphous phase chains is realized at room temperature through cooperative micro-Brownian motions with short relaxation times. Taking into account that covalent-bound sections of the chains of the amorphous phase can enter the crystallites, the noted mobility may initiate changes in the size of the latter. Such a possibility is proved by the example of the noted copolymer. At low-temperature crystallization of a vinylidene fluoride - hexafluoropropylene copolymer from a solution the formed alpha-phase crystals have little perfection. The size of the crystals increases when the films are stored in room conditions. Because of the crystal polymorphism, at the same time a certain fraction of gamma-phase crystals which are present in initial films undergo a polymorphic transformation gamma -> alpha. These processes lead to an increase in crystallinity. Moreover, during such processes additional structuring is observed, which is reduced to the displacement of various kinds of intra-chain defects into the amorphous phase (and especially into the surface). Since the copolymers under study are ferroelectrics, they were studied by piezo force microscopy. It was found that despite the crystallization predominantly in nonpolar alpha-phase, piezo force microscopy revealed a domain structure, which formation mechanism is discussed. The structural changes at physical aging of the films affect the character of the noted domain structure. Thus, it is suggested that the mechanism of the described structural changes is realized through the developed cooperative mobility of the chains in the amorphous phase, which characterizes the processes of rotational diffusion.

The structural and electrophysical characteristics of poly (vinylidene fluoride-hexafluoropropylene) copolymer films with hexafluoropropylene content 8.3 mol%, obtained by low-temperature crystallization from various solvents, have been investigated. X-ray diffraction data indicate that the films crystallized mainly in the α-phase. When acetone is used as a solvent, the degree of crystallinity is the lowest due to the rapid escape of solvent molecules from solution. IR spectroscopic data showed that the amorphous phase of such films is enriched with T3GT3G− isomers. This is accompanied by an increase in their high-voltage conductivity. Despite the crystallization mainly in nonpolar α-phase, a domain structure was recorded in the films by piezo force microscopy. Surface structuring processes, accompanied by the displacement of certain attachment chain defects into the surface, have been recorded using IR spectroscopy. The presence of such intrachain defects is confirmed and characterized by high-resolution 19F NMR.

The coordination properties of 3,4-bis(diphenylphosphinyl)-2,5-dimethylhexa-2,4-diene (L-2) were studied in relation to manganese(II) chloride and perchlorate complexes. Manganese(II) chloride forms 1 : 1 complex with bis-phosphine oxide L-2, while the composition of the manganese(II) perchlorate complex is 2 : 1. The crystal structures of bis-phosphine oxide L-2 complexes with manganese dichloride (CCDC no. 2165179) and manganese perchlorate (CCDC no. 2165180) were determined by X-ray diffraction.

Amphiphilic diblock copolymers (DCs) of 2,3,4,5,6-pentafluorostyrene (PFS) and 2-hydroxyethyl methacrylate (HEMA) of different composition and molecular weights were prepared by two-step reversible addition-fragmentation chain transfer (RAFT) polymerization and first used for preparation of superhydrophobic coatings for cotton/polyester fabrics. The transition from hydrophobic to superhydrophobic coatings is controlled by the ratio between poly(2,3,4,5,6-pentafluorostyrene) (PPFS) block and poly(2-hydroxyethyl methacrylate) (PHEMA) block lengths (P-n(PFS)/P-n(HEMA)). The increase inP(n)(PFS)/P(n)(HEMA)is accompanied by a significant increase in water (theta(H)(O)(2)) and diiodomethane (theta(CH)(I)(2)(2)) contact angles, which reach the plateau atP(n)(PFS)/P-n(HEMA)= 3.5 and remains almost constant up toP(n)(PFS)/P-n(HEMA)= 6.2. Surface modification of the cotton/polyester fabric with the DC havingP(n)(PFS)/P-n(HEMA)= 6.2 produced superhydrophobic surface with theta(H)(O)(2)= 158 +/- 4 degrees and contact angle hysteresis CAH = 5 +/- 2 degrees, and theta(CH)(I)(2)(2)= 107 +/- 3 degrees.