Julia V. Kostina’s research while affiliated with A.V. Topchiev Institute of Petrochemical Synthesis and other places

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.

Research of coloring pigments and binding compounds from the Upper Palaeolithic (UP), including on portable art objects such as personal ornaments, provides new insights into social and cultural aspects of human history. However, we lack a comprehensive study of the composite pigment mixtures and binding materials that were produced intentionally and used for coloration. The study of several personal ornaments from the UP layers dated 31-23 ka calBP in Mezmaiskaya Cave, North Caucasus (Russia), shows that UP paints have a complex chemical composition. Using ATR-FTIR and SEM-EDS, we have identified that for coloring organic personal decorations UP humans used composite paint mixtures produced from organic (bitumen) and inorganic (red bolus/kaolin) natural pigments. Also, we firstly identified that UP humans applied a proteinaceous binder, likely representing a kind of the gelatine type animal glue, which they intentionally produced from animal origin materials using boiling. This is the oldest evidence of boiling placing its origin at about 30 ka within the late UP and linking this innovation to the need of producing organic binding material for dyeing rather than with the food preparation.

Poly(vinyl trimethylsilane) (PVTMS) films were subjected to direct surface fluorination in liquid medium (perfluorodecalin). The samples were investigated using several techniques: SEM-XEDS, XPS, ATR-IR, and contact angle measurement. The methods used allowed us to estimate chemical changes occurring because of the treatment. ATR-IR showed that most of the changes occurred in the Si(CH3)3 group. Monofluorinated Si(CH3)3 groups formed in the near-surface layer (Ge crystal, 0.66 µm penetration) after 30 min of fluorination, and then di- and trifluorinated groups appeared. Oxidation of the film with oxygen was also shown with the use of ZnSe crystal (2 µm penetration). The XPS method allowed an assessment of the ratio of the main elements at the surface of the fluorinated film. Two different exponential models were proposed to fit the experimental data of SEM-XEDS. Based on the model with the intercept, the depth of fluorination was estimated to be ≤1.1 µm, which is consistent with the result from the literature for the gas-phase fluorination. Contact angle measurements showed that oxidation of the PVTMS surface prevailed for the first 45 min of fluorination (surface hydrophilization) with a subsequent fluorine content increase and hydrophobization of the surface upon 60 min of fluorination.

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.

A direct fluorination technique was applied for the surface treatment of PIM-1 films in a liquid phase (perfluorodecalin). The fluorinated samples were analyzed by various instrumental techniques. ATR-IR spectroscopy showed that the fluorination predominantly takes place in methylene- and methyl-groups. Cyano-groups, aromatic hydrogens and the aromatic structure of the PIM-1 repeat unit were shown to be relatively stable at the fluorination conditions. XPS confirmed that the concentration of fluorine, as well as oxygen, in the near surface layer (~1 nm) increases with fluorination time. C1s and O1s surface spectra of the fluorinated PIM-1 samples indicated an appearance of newly-formed C-F and C-O functional groups. Scanning electron microscopy and X-ray energy-dispersive spectroscopy of the fluorinated PIM-1 samples showed an increase of the fluorine concentration at the surface (~0.1–1 μm) with the treatment duration. Analysis of the slices of the PIM-1 films demonstrated a decline of the fluorine content within several microns of the film depth. The decline increased with the fluorination time. A model of fluorine concentration dependence on the film depth and treatment duration was suggested. A change in the specific free surface energy as a result of PIM-1 fluorination was revealed. The fluorination time was shown to affect the surface energy (γSV), providing its shift from a low value (25 mJ∙m⁻²), corresponding to tetrafluoroethylene, up to a relatively high value, corresponding to a hydrophilic surface.

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.

Poly-2,6-dimethylphenylene oxide (PPO) film samples with varying degrees of crystallinity (from 0 to 69%) were obtained by means of different techniques. The films were studied by various physicochemical methods (Fourier-transform infrared spectroscopy, positron annihilation lifetime spectroscopy, X-ray diffraction, and ¹H nuclear magnetic resonance relaxation). Solubility coefficients of gases in the PPO samples were measured via sorption isotherms of gases by volumetric technique with chromatographic detection. The apparent activation energy of permeation and the activation energy of diffusion of all gases were estimated based on temperature dependences of gas permeability and diffusivity for amorphous and semi-crystalline PPO in the range of 20–50 °C. The peculiarities of free volume, density, and thermal properties of gas transport confirm the nanoporosity of the gas-permeable crystalline phase of PPO. So, the PPO can be included in the group of organic molecular sieves.