The study exlores the possibility of using organomineral complexes, obtained as a result of adsorption of the macromolecular biocides (polyguanidines) on the montmorillonite surface, to protect composites based on plasticized polyvinyl chloride from photooxidative degradation and biofouling. According to UV spectro-scopy data and the results of measurements of the intrinsic viscosity of polymer solutions, it has been found that the introduction of organomineral complexes into the material helps to reduce the extent of photooxidative degradation of the material under conditions of hard UV irradiation. The organomineral complexes used effectively suppress the fouling of the composites by biofilms of the micromycete Yarrowia lipolytica 367-3. The mechanical characteristics of composites containing organomineral additives are maintained at a high level after thermal aging (in accordance with the technical documentation for the material). The composites also meet the technical documentation requirements for weight loss on heating, density, and volume resistivity, but increasing the concentration of the organomineral additive in the composite above 2 wt

The possibility of using organomineral complexes of polyhexamethylene guanidine hydrochloride as a functional additive for a waterborne paint based on polyvinyl acetate has been investigated. Organomineral complexes containing 20 and 30 wt % guanidine polymer have been obtained, with intercalation of polyguanidine chains into the interlayer space of montmorillonite being observed. It has been revealed that the stability of the polymer film to water is retained when organomineral complexes are introduced into a polyvinyl acetate dispersion, whereas the water resistance of the film sharply decreases when free polyguanidine is added. There was no significant influence of organomineral complexes on the rheological characteristics of the dispersion and its sedimentation stability. Testing of waterborne paints with various additives has shown that introduction of organomineral complexes into the material prevents the coating from fouling by biofilms of gram-positive bacteria Staphylococcus aureus and Rhodococcus erythropolis , with the hardness, water resistance, and water-vapor transmission of the coatings being retained at a satisfactory level.

A series of biocide-containing polyethylene composites were obtained using novel guanidine-containing copolymers immobilized on an inert mineral carrier. Multispecies microbial communities were isolated from the surface of polyethylene samples either incubated or found in the environment, and their taxonomic composition was determined. Biofilms reconstructed using microorganisms obtained from different ecotopes were shown to intensively foul polyethylene surfaces. The presence of polyguanidine biocide suppressed the growth and survival of both binary and multispecies biofilms, with a cumulative effect during long-term incubation. When microorganisms were co-cultivated in binary biofilms, the phenomenon of a decrease in biocide effectiveness was demonstrated. This protective effect is potentially based on cooperative interactions inside the binary biofilm community. Scanning electron microscopy showed a pronounced difference in the architecture of reconstructed biofilms incubated in the presence of biocide in comparison to control samples, where biocide suppressed the formation of dense and well-organized three-dimensional structures. Biofilm disruption by immobilized biocides occurred primarily during the later stages of biofilm formation, probably caused by polycation interaction with their negatively charged extracellular components.

Проведены лабораторные и натурные испытания стойкости композита на основе полиэтилена низкой плотности с органоминеральной биоцидной добавкой к воздействию водных сред. В качестве органоминеральной добавки использован полигексаметиленгуанидин гидрохлорид (высокомолекулярный нетоксичный биоцид, применяемый в составе антисептических растворов), иммобилизованный на неорганическом носителе (монтмориллоните) для улучшения качества распределения органоминеральной добавки в термопластичном полимере (без потери биоцидных свойств полигуанидина) и для предотвращения вымывания полигуанидина из композита при эксплуатации. Состав и структура композита с органоминеральной добавкой сохраняются без изменений после экспонирования в дистиллированной воде и в модельной морской воде. Натурными испытаниями композитов в морской воде на глубине 1.5 м в тропическом климате установлено, что даже после 21 месяца экспонирования образцов вымывания полигуанидина из материала не наблюдается. При этом образцы без органоминеральной добавки подвергаются незначительному фотоокислительному старению, тогда как молекулярная структура полимера в композите с добавкой не изменяется. Таким образом, исследуемая органоминеральная добавка оказывает фотостабилизирующее действие на полиэтилен. При экспонировании образцов в морской воде происходят незначительное снижение прочности образцов и увеличение модуля упругости, что связано с повышением степени кристалличности полиэтилена при старении.

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.

With the help of spectroscopic and differential scanning calorimetry (DSC) techniques, we have studied conformational and phase reorganizations as function of temperature in intercalated polymer-clay nanocomposites based on low-, middle-, and high-density polyethylene (PE) matrices. We show that Raman spectroscopy is sensitive to structural changes appearing during heating at much lower temperatures (about 47 °C) in comparison to DSC measurements. In fact, in the melting region where DSC traces show endotherms, Raman spectra reveal dramatic changes in the phase and conformational compositions of PE and PE-matrices within PE-clay nanocomposites. Noteworthy, the structural reorganization pathway, through which the semicrystalline nanocomposites transform into a melt state, depends primarily on the PE density and weakly on the filler (nanoclay). Moreover, the temperature-dependent crystallinity degree and the total amount of trans -conformers of the PE system are determined, and the evidence for the formation of intermediate crystal-like phase during heating is shown.

Hydrogels prepared from L-cysteine, silver acetate, and polyhexamethyleneguanidine hydrochloride (PHMG-HC) were used in rheological, structural, and antibacterial studies. Aqueous solutions of Lcysteine and silver acetate were found to be very miscible with aqueous solutions of PHMG-HC to form transparent hydrogels. A model for the three-dimensional structure of the gel network was proposed. The hydrogel exhibited high antimicrobial activity against test cultures of pathogenic and conditionally pathogenic microorganisms.

In this issue, the Editorial Board of Laser Physics is happy to offer to our readers a special series of articles dedicated to the memory of Professor Pavel P Pashinin and his successful endeavor in the field of laser physics. Pavel P Pashinin (1935–2020), a Corresponding Member of the Russian Academy of Sciences, was a distinguished member of the founding team of laser physicists in Russia, led by a winner of the 1964 Nobel Prize in physics, Alexander M Prokhorov. For many years, Prof. Pashinin headed the ‘Interaction of Coherent Radiation with Matter’ Department at the Institute of General Physics in Moscow. The pioneering works of Prof. Pashinin on lasers and their applications and the research results of his department are widely known and recognized by the international scientific community. In 2002, after the death of AMProkhorov, Prof. Pashinin became the Editor-in-Chief of the International Journal ‘Laser Physics’ (LP). Since 2004 Prof. Pashinin has also undertaken chief editorship of the newly created journal ‘Laser Physics Letters’ (LPL). In addition to his scientific and editorial work, Prof. Pashinin had actively participated in organizing and running the Annual International Laser Physics Workshop (LPHYS). The workshop had been closely associated with both journals, LP and LPL. This world-renown conference started in 1992 and, since then, has taken place every consecutive year, except for 2020, when it was postponed due to the world covid pandemic. From 2003 to 2019, all LPHYS Workshops were chaired by Prof. Pashinin. Under his leadership, both the LP and LPL journals and the LPHYS Workshop became widely recognized and accepted worldwide. The Workshops were held annually in many countries in Europe, Asia, and South and North America. The following is the list of issue-related articles.

This study aimed to investigate the dependence of the biocidal activity of polyguanidine (co)polymers on their structure during the formation of biofilms by active PE-degrading cultures of model microorganisms. The Bc-2 copolymer of methacryloyl guanidine hydrochloride (MGHC) and diallyldimethylammonium chloride (DADMAC), which suppressed both the formation of biofilms and the growth of planktonic cultures, exhibited the highest activity. When PE was exposed in tropical soil, the composition of the microbial community on the PE surface differed significantly from that of the community in the surrounding soil. In particular, the proportion of Actinobacteria increased from 7% to 29%, while the proportion of Bacteroidetes decreased from 38% to 8%. Keywords: biofilms, polyhexamethylene guanidine salts, dynamics of biofilm formation, antibiofilm effect, composite materials

During radical polymerization of novel biocidal methacrylate guanidine monomers, a cyclic byproduct was discovered and identified as 2-imino-5-methyltetrahydropyrimidin-4(1H)-one (THP). Its methacrylate salt (MTHP) was synthesized and characterized via 1H and 13C NMR and pyrolysis chromatography. Synthesis conditions of both THP and MTHP were optimized to high yields, and both MTHP homopolymerization (in aqua) and copolymerization with diallyldimethylammonium chloride (in aqua in salt form) were successfully carried out with middle to high yields, providing a promising platform for potential tailored biocide polymers.

In accordance with the suggested procedure, the strength characteristics of polymers prepared by radical polymerization of vinyl polymers are enhanced by grafting the monomers to the nanofiller surface. When preparing high-strength polymer–aluminosilicate nanocomposites by radical polymerization in situ, it is appropriate to ensure both grafting of polymer chains to the aluminosilicate surface of the filler (montmorillonite) and hydrophobization of the nanofiller surface. To solve this problem, successive modification of montmorillonite with two quaternary ammonium salts with different properties was studied. Fillers with mixed modifiers were prepared, and their structure was determined. Studies of composites with such fillers confirmed the appropriateness of using the mixture of modifiers for preparing the filler: The nanocomposite based on butyl methacrylate, containing organoclay with the mixed modifier, surpasses in the Young’s modulus both unfilled poly(butyl methacrylate) and composites containing nanoclays with the individual modifiers.

The possibility of using one-pot melt blending for the synthesis of polymer-aluminosilicate nanocomposites from heterogeneous polymer blends is studied. The polyolefin composition containing recycled polyethylene and designed for the anticorrosion protection of pipelines is used as a polymer matrix. The advisability of using one-pot blending procedure for the synthesis of composites from polymers processed by extrusion is substantiated. Formation of the intercalated structure of the nanocomposite in the system under consideration is verified experimentally. The nanostructure of an organoclay in the composites obtained by the conventional method (polymer blending with organoclay) and the one-pot procedure (polymer blending with natural clay and organomodifier) is found to be almost the same. It is shown that the physicomechanical characteristics of the nanocomposites synthesized by different methods are also similar. Resistance of organoclay structure formed in the polymer composite against sodium chloride aqueous solution is investigated by X-ray diffraction. It is revealed that the structure of the nanocomposites obtained by different methods remains almost unchanged during their swelling in water and subsequent drying which provides evidence that modification of the clay during blending with the polymer matrix is complete and the composite does not contain nonmodified clay swelling in water.

Various steps of the formation of nanocomposite coatings using organic-soluble film-forming agents are accompanied by changes in the structure of the aluminosilicate nanofiller under the action of various factors. Taking these factors into account is necessary for the development of coatings of preset structure with optimum properties. Swelling of various organoclays in pure and technical solvents and in a solution of an alkyd oligomeric film-forming agent was studied. The stability of organoclay dispersions in these media, the nanostructure of organoclay tactoids in dispersions, and the nanostructure of films of cured composites based on the alkyd oligomer were correlated. Factors favoring the swelling of organoclays in a film-forming agent solution and the formation of an intercalated nanocomposite were revealed. The effect of water vapor on the nanofiller structure in the composite film was characterized to evaluate the moisture resistance of the composite.

A series of samples with different morphology is obtained by the monolithization of an ultrahigh molecular weight polyethylene nascent powder at different temperatures. The elastoplastic properties of films pressed at 135°C that have the greatest ability to achieve high orientational elongations are studied in detail. It is shown that the deformation of ultrahigh molecular weight polyethylene crystals at elevated temperatures contains a noticeable elastic component and, at the time of unloading of the stretched “spatulas,” their elastic contraction occurs; as a result, the residual elongation and disorientation of chains decrease. Relaxation processes can be reduced if the deformable sample with fixed ends is cooled rapidly. Orientational crystallization during thermal fixation promotes an increase in the degree of crystallinity and the Hermans orientation factor and, accordingly, facilitates improvement in the mechanical properties of the sample.

Blends of isotactic PP and HDPE of various compositions are prepared by melt extrusion in two crystallization modes. The first series of composites is obtained by a rapid cooling of the melt (≈8000°C/min). According to X-ray diffraction and microscopy studies, pure PP forms a smectic mesophase under these conditions. In contrast, the PP component in the blends crystallizes in the form of monoclinic α crystals into spherulites with a diameter of ~4–5 µm. The PE component of the composites has a lower enthalpy of melting than pure PE, and it decreases with an increase in the PP content in the system. This may be due to formation of the interphase layer where PE and PP molecules are intermixed at the molecular level. Estimation according to the Gelfand theory shows that the thickness of the boundary layer in the composites of the first series is about 30 nm. The second series of composites is obtained by a slow cooling of the melt (≈2°C/min). All samples of this series contain large (~80–120 µm) radial spherulites, but in the blends, their size is somewhat smaller than that in pure PP. The enthalpy of melting of PE and PP components in the blends of the second series does not depend on composition and is equal to the corresponding values for pure PE and PP. Apparently, upon slow cooling of the melt of two polyolefins, the molecules from the interphase layer have time to move to the corresponding domains and an ordinary two-phase system without a “transition” zone is formed. Owing to the developed interfacial zone in the composites of the first series, the phases are deformed together and these materials show a good deformation behavior. In the composites of the second series, all mechanical parameters are worse than those of pure polymers and blends of the first series (the “antagonistic effect”) because of the absence of an extended boundary layer.

The possibility of solid-state solvent-free modification of Na+-montmorillonite by transition metal salts (NiCl2 center dot 6H(2)O, CoCl2, FeCl3 center dot 6H(2)O) and quaternary ammonium salts (cetyltrimethylammonium bromide, diocta-decyldimethylammonium chloride, alkylbenzyldimethylammonium chloride) was investigated in the presence of water or ethanol. The introduction of water or ethanol was necessary for the effective modification, small amounts (4-8 mmol per 2 g clay) were sufficient, as was the crystallohydrate water in the case of FeCl3 center dot 6H(2)O. Solid-state intercalation produces metal cation-and organo-modified montmorillonites (M-Mt and O-Mt), which were studied by wide-angle X-ray diffraction (WAXD), wavelength dispersive X-ray fluorescence analysis (WDXRF) and thermal analysis (TGA). On mechanochemical interaction during grinding Na+ and Ca2+ were exchanged for intercalant cations, the residual amount of initial cations in the rinsed modified montmorillonite did not exceed 0.1-0.2%, measured by WDXRF, and NaCl was produced as a distinct WAXD phase in quantities consistent with WDXRF, from 3.0% to a theoretical maximum of 5.6%. M-Mt were identical in structure and composition to ones obtained by solution modification. For O-Mt, the intercalation and modification proceeded to a larger extent compared to solution-modified and commercial equivalents, and with a substantially higher basal spacing (by 2-3 nm) and modifier content. The products were obtained as fine powders that did not require subsequent dispersion and fractional separation.