Understanding the molecular interactions between solvent components and polymer chains is crucial to advancing high-performance fiber technologies. Here, we combine vibrational spectroscopy, quantum-chemical modeling, rheological analysis, and controlled stretching experiments to unravel the fundamental role of dimethyl sulfoxide-water interactions in polyacrylonitrile (PAN) solutions. Infrared spectroscopy reveals distinct signatures of solvent-solvent and solvent-polymer hydrogen bonding, which are rationalized by quantum-chemical calculations and correlated to macroscopic rheological behavior. The molecular picture obtained explains the non-trivial dependence of viscoelasticity and fiber drawability on the water content. Moreover, stretching experiments under different humidity conditions directly demonstrate how nanoscale solvent structuring translates into the tunable mechanical performance of PAN fibers. This integrated approach establishes a clear link among molecular solvation, processability, and final fiber properties, opening new opportunities for the design of advanced precursors for carbon fibers.

Concentrated solutions of polycarbosilane (PCS) are critically important for the development of continuous SiC precursor fibers, where solvent-polymer interactions govern rheology, viscoelastic stability, and spinnability. In this work, PCS solutions in two nonpolar hydrocarbon solvents with different molecular architectures as linear n-heptadecane and bicyclic decalin were systematically investigated over a wide concentration range, with emphasis on the semi-dilute entangled and concentrated regimes relevant to solution-based fiber spinning. A combined experimental approach involving steady and oscillatory rheometry and Fourier transform infrared (FTIR) spectroscopy was used to elucidate the influence of solvent structure on solvation, viscoelastic response, microstructural organization, and local intermolecular interactions. Despite similar dilute-solution interaction parameters, the concentrated regimes exhibit pronounced solvent-dependent differences in elasticity and flow behavior. For the first time, linear heptadecane is identified as a viable and technologically promising solvent for PCS, enabling the formation of thermostable homogeneous concentrated solutions with enhanced deformability. This behavior opens a realistic pathway toward a new solution-based fiber-spinning route based on elasticity-controlled processing. The results demonstrate that solvent molecular geometry governs the structure-rheology-processability relationship of concentrated PCS systems rather than solubility parameters alone, providing a new framework for solvent selection in SiC precursor fiber technologies.

For the first time, electrospinning has been used to recycle polyacrylonitrile terpolymer (PAN) waste following the solid-phase N-methylmorpholine-N-oxide (NMMO) process from PAN solutions in DMSO into nonwoven materials. The morphology of the obtained material has been studied. The material derived from secondary raw materials was compared to the material from the original PAN using IR spectroscopy, X-ray diffraction, scanning electron microscopy, and atomic force microscopy. It has been demonstrated that the chemical changes of PAN that occur during NMMO processing do not interfere with nonwoven material manufacture. Spun PAN nonwovens with different histories have similar morphology. It has been shown that the elastic modulus of ultrafine fibers depends on the history of PAN. Single monofilaments produced from initial PAN have a threefold greater elastic modulus than fibers spun from NMMO-recycled polymer. The revealed structure and properties of PAN fibers allow them to be considered as filter materials, as well as precursors of carbon nonwoven fabrics.

Absorption with aqueous amine solvents is a well-established technology for acid gas removal and will continue to be a readily available option for post-combustion CO2 capture. Its main drawback is the solvent degradation under process conditions, due to oxygen captured from the flue gases. Dissolved O-2 oxidizes amines, forming various degradation products, including heat-stable salts (HSS), which intensify corrosion and reduce the sorption capacity of the solvent. This paper investigates direct removal of dissolved O-2 from amine solvents in gas-liquid membrane contactors. Novel composite membranes have been developed for this process. They consist of a highly permeable polymer blend, made from poly [1-(trimethylsilyl)-1-propyne] (PTMSP) and polyvinyltrimethylsilane (PVTMS), which is deposited as a thin protective layer on porous polysulfone hollow fibers and tubular ceramic supports. For the first time, a comprehensive study has been carried out on the efficiency of dissolved O-2 removal vs. contactor and process parameters (membrane support type; amine solvent type; solvent CO2 loading; driving force generation mode; solvent velocity; temperature). The deoxygenation performance of the contactors has been demonstrated in the O-2 removal process from the amine solvent under the conditions encountered in an absorber sump during the CO2 capture process (30 % aqueous monoethanolamine solvent with CO2 loading of 0.5 mol/mol at 60 degrees C). In this case, the O-2 removal efficiency of up to 46 % in an hour has been achieved for developed contactors, which reduces the estimated rate of HSS formation by similar to 2 times compared to non-deoxygenated solvents. The size of the membrane was calculated to remove 90 % of the dissolved oxygen in a hypothetical post-combustion CO2 capture plant with a solvent flow rate of 120 m(3)/h, amounting to similar to 1460 m(2) for ceramic-based membranes.

Formation of cocrystals in polymer-containing systems attracts a lot of attention lately due to their promise in pharmaceutics, being a poorly studied phenomenon in polymer science. For the first time, we report on the cocrystallization in mixtures of polyethylene oxide and thymol and study in detail the structure and thermal behavior of the mixtures by differential scanning calorimetry, optical microscopy, wide angle X-ray scattering, attenuated total reflection Fourier-transformed infrared spectroscopy, and quantum chemical simulation. The results are summarized into the experimental phase diagram that describes well all the transformations of the systems during their heating and cooling. On the molecular level, we conclude the existence of noncovalent-bonded complexes composed of three monomeric units of polyethylene oxide and two molecules of thymol, which might become structural units of cocrystals upon cooling. This results in a growth of huge centimeter-sized spherulites in the stoichiometric mixture and to the coexistence of two types of spherulites in the mixtures of other compositions. The peculiarities of thymol release from the complexes into different media are also investigated.

The structure and properties of the new material derived from binol (BCA), multifunctional chiral additive to liquid crystals (LC) with a high optical activity and the presence of free carboxylic groups in the molecule, are studied. The analysis of the thermal behavior of BCA is done by means of DSC, rheology methods, dielectric, and IR spectroscopy. The agreement between the rheological and dielectric data indicates the similar relaxation mechanisms, described within the WLF model. The analysis of the IR spectra proves the change in dielectric and rheological parameters induced by the variation in the structure of associates of hydrogen-bonded complexes. The modification of the sizes and quantity of the connected structures with the temperature may result in the possible appearance of nonlinear effects in LC composites associated with the simultaneous complex change in the dielectric and rheological properties.

The paper discusses experimental techniques for pulping, bleaching, and creating manmade fibers based on Na-sulfite and Mg-bisulfite dissolving pulps utilizing a dry-jet wet spinning procedure with solutions in N-methylmorpholine-N-oxide. After pulping, Mg-bisulfite pulp had a cellulose yield of 46.1

A method for obtaining nonwoven carbon materials by the staged heat treatment of cellulose felt is developed. Fabrics produced from fibrous flax cellulose and viscose fibers by needle punching are used as nonwoven precursors. To obtain carbon fabric precursors the optimum ratios of components are chosen from the data on the formation of nonwoven fabrics and the thermal analysis of various blend formulations. It is shown that the content of flax fibers in the system should be at least 50%. Viscose fibers play the role of a reinforcing material and so far cannot be fully excluded from the system. With an increase in the content of flax cellulose the value of carbon yield grows. The mechanical properties of the carbon felt are provided by the physical network of friction and dispersion contacts between individual fibers. Upon heat treatment of the composite nonwoven material, the morphological features of precursor fibers remain unchanged. The interplanar distances of carbon layers in the carbon material are calculated using X-ray diffraction analysis and transmission electron microscopy. The fraction of carbon upon heat treatment to 1700°С is at least 90%, and after graphitization to 2400°С the purity of the product is above 99%. The maximum values of carbon yield at this temperature may be as high as 25‒27%. The coefficients of thermal conductivity of the carbon felt are measured, and the values obtained are 30% lower than the corresponding parameters of carbon fabrics.

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.

Membrane gas–liquid contactors have great potential to meet the challenges of amine CO2 capture. In this case, the most effective approach is the use of composite membranes. However, to obtain these, it is necessary to take into account the chemical and morphological resistance of membrane supports to long-term exposure to amine absorbents and their oxidative degradation products. In this work, we studied the chemical and morphological stability of a number of commercial porous polymeric membranes exposed to various types of alkanolamines with the addition of heat-stable salt anions as a model of real industrial CO2 amine solvents. The results of the physicochemical analysis of the chemical and morphological stability of porous polymer membranes after exposure to alkanolamines, their oxidative degradation products, and oxygen scavengers were presented. According to the results of studies by FTIR spectroscopy and AFM, a significant destruction of porous membranes based on polypropylene (PP), polyvinylidenefluoride (PVDF), polyethersulfone (PES) and polyamide (nylon, PA) was revealed. At the same time, the polytetrafluoroethylene (PTFE) membranes had relatively high stability. On the basis of these results, composite membranes with porous supports that are stable in amine solvents can be successfully obtained to create liquid–liquid and gas–liquid membrane contactors for membrane deoxygenation.

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.

In this work, we studied aqueous solutions of monoethanolamine (MEA), which are widely used to remove CO2 from flue and oil gases. This study combined experimental and theoretical methods of vibrational spectroscopy, using high-temperature infrared spectroscopy, quantum-chemical calculations of theoretical vibrational spectra, and structural electronic and energy characteristics of model structures. MEA has a propensity to form associations between various compositions and structures with water molecules, as well as those composed solely of water molecules. The structural and energy characteristics of such associates were analyzed in terms of their ability to interact and retain carbon dioxide. The influence of elevated temperatures and concentration of aqueous MEA solution on change in the structure of associates has also been investigated. An analysis of theoretical and experimental vibrational spectra allowed us to examine the IR spectra of MEA solutions, and identify the bands responsible for the formation of associates that would sorb CO2 well, but would delay its desorption from the solution.

The authors discuss functional characterization of Mousterian tools on the basis of their use-wear and residue analysis of five lithic tools from Mezmaiskaya cave and Saradj-Chuko grotto in the North Caucasus. The results represent the first comprehensive use-wear and residue analysis carried out on Mousterian stone artefacts in the Caucasus. This study unequivocally confirms the use of bitumen for hafting stone tools in two different Middle Paleolithic cultural contexts defined in the Caucasus, Eastern Micoquian and Zagros Mousterian.

The application of gas-liquid membrane contactors for ethane-ethylene separation seems to offer a good alternative to conventional energy-intensive processes. This work aims to develop new hydrophobic composite membranes with active ethylene carriers and to demonstrate their potential for ethylene/ethane separation in gas-liquid membrane contactors. For the first time, hybrid membrane materials based on polyoctylmethylsiloxane (POMS) and silver tetrafluoroborate, with a Si:Ag ratio of 10:0.11 and 10:2.2, have been obtained. This technique allowed us to obtain POMS-based membranes with silver nanoparticles (8 nm), which are dispersed in the polymer matrix. The dispersion of silver in the POMS matrix is confirmed by the data IR-spectroscopy, wide-angle X-ray diffraction, and X-ray fluorescence analyses. These membranes combine the hydrophobicity of POMS and the selectivity of silver ions toward ethylene. It was shown that ethylene sorption at 600 mbar rises from 0.89 cm3(STP)/g to 3.212 cm3(STP)/g with an increase of Ag content in POMS from 0 to 9 wt%. Moreover, the membrane acquires an increased sorption affinity for ethylene. The ethylene/ethane sorption selectivity of POMS is 0.64; for the membrane with 9 wt% silver nanoparticles, the ethylene/ethane sorption selectivity was 2.46. Based on the hybrid material, POMS-Ag, composite membranes were developed on a polyvinylidene fluoride (PVDF) porous support, with a selective layer thickness of 5–10 µm. The transport properties of the membranes were studied by separating a binary mixture of ethylene/ethane at 20/80% vol. It has been shown that the addition of silver nanoparticles to the POMS matrix leads to a decrease in the ethylene permeability, but ethylene/ethane selectivity increases from 0.9 (POMS) to 1.3 (9 wt% Ag). It was noted that when the POMS-Ag membrane is exposed to the gas mixture flow for 3 h, the selectivity increases to 1.3 (0.5 wt% Ag) and 2.3 (9 wt% Ag) due to an increase in ethylene permeability. Testing of the obtained membranes in a gas-liquid contactor showed that the introduction of silver into the POMS matrix makes it possible to intensify the process of ethylene mass transfer by more than 1.5 times.

The production of long flax fiber for the subsequent production of textile yarn is accompanied by the formation of a significant amount of waste—noils, which is a mechanical mixture of long and short flax fibers and shives. Comparative studies of the structure and chemical composition of the fibrous fraction of noils and shives were carried out using IR spectroscopy. The solubility of shives and flax noils in N-methylmorpholine-N-oxide (NMMO) was studied, a comparative analysis of the rheological behavior of solutions of flax and wood cellulose was carried out and the optimal temperature–concentration conditions for obtaining flax fibers from noils were determined. It was shown for the first time that using the method of solid-phase activation of the cellulose-solvent system makes it possible to obtain fibers in a short period of time (no more than 10 min). The structure of both the raw material and the resulting fibers was studied by X-ray diffraction analysis. The thermal properties of a new type of cellulose fibers was evaluated. The complex of the conducted studies allows us to consider flax fibers from noils along with flax fibers from long-staple flax, as a real alternative to fibers from wood pulp.

Quantum chemical calculations and FTIR spectroscopic studies show that β-(2,4,7-trinitro-9fluorenylideneiminooxy)propionic acid (TNF-carb) can act as an electron acceptor. It stabilizes charge transfer complexes with discotic triphenylene-containing molecules. Complexes TNF-carb/discotic may have different compositions (up to 1/4) and stabilize their structure via π–π interaction, but with the complementary hydrogen bonding as well.

Amine absorption processes designed to remove acid gases from gas streams generally face a major challenge of solvent degradation. This degradation leads to the formation of heat-stable salts (HSS), corrosive agents that irreversibly bind free alkanolamine. The present study proposes, for the first time, a method for HSS perstraction using a liquid–liquid membrane contactor that allows HSS to transfer through porous membranes from the solvent into a hydrophobic extractant represented by a methyltrioctylammonium solution in 1-octanol. The perstraction provides selective extraction of HSS anions without direct mixing of liquid phases or the formation of stable emulsions of the solvent and the extractant. For this purpose, a number of industrial and laboratory porous membrane samples fabricated from polyvinylidene fluoride, polypropylene, and polysulfone were investigated. Their chemical and morphological stability, surface properties, and transport properties were tested under prolonged (>600 h) contact with a model solvent (an aqueous monoethanolamine solution) and with the components of the selective extractant. The feasibility of HSS perstraction was demonstrated using the formic acid (as an HSS model) extraction from the model solvent. The most promising results were obtained for a system with a polyvinylidene fluoride membrane: up to 50% of formic acid was extracted over 18 h.

Herein we present a Ca[EDTA]-based synthesis and comparative study of perfectly shaped plate-like, rod–like, and prism-like carbonated apatites.