Mykola T. Kartel

Nanostructured carbon materials, such as graphene, oxidized graphene, and graphene oxide doped with nitrogen and sulfur heteroatoms, have specific physicochemical properties and can be used in various fields from electronics to medicine. Formed carbon nanoparticles are difficult to dope (especially oxidized graphene or graphene oxide) in such a way that they retain their structure as a whole. Therefore, it is promising to obtain precursors of these nanoparticles that are already doped with the desired heteroatom. Rolled or pressed materials from expanded graphite (EG) can be a precursor for obtaining such nanoscale materials by anodic exfoliation in electrolytes. Therefore, the development of methods for the synthesis of EG containing nitrogen and sulfur heteroatoms is the goal of this work. The paper deals with the synthesis and study of the physicochemical properties of graphite intercalation compounds (GICs) formed by their interaction with concentrated nitric and sulfuric acids, as well as their mixtures in various ratios. The main characteristics of the resulting GICs were determined and their capability to expand thermally was examined. It was shown that GICs with sulfuric acid have a better ability to expand and allow obtaining better quality EGs. EG samples obtained from these GICs were characterized by X-ray photoelectron spectroscopy (XPS) and derivatography. It was determined that during thermal expansion of co-intercalated graphite compounds, nitrogen and sulfur atoms are incorporated into the graphene planes of EG particles. It was shown that this method can be used to obtain EG doped with sulfur heteroatoms (0.2–0.5 at. %) mainly in sulfite and sulfate groups and nitrogen (0.6–1.2 at. %) mainly in the pyrrolic and quaternary chemical states, the content of which can be regulated by changing the ratio of sulfuric and nitric acids in the intercalating mixtures.

The paper presents a number of properties of unsaturated polyester resins based on the post-consumer PET recyclate modified with iron(II) clathrochelate, such as thermal, mechanical, optical and visual. The iron compound was used as an accelerator instead of toxic low-molecular cobalt salts, commonly applied for curing of unsaturated polyester resins being also responsible for giving the resin materials an orange-red colour depending on the used amount. Moreover, the iron clathrochelate proved to be an ideal agent added to the polyester resin, giving it antimicrobial properties. Cytotoxicity tests showed that the tested materials were safe and did not cause any undesirable effects in contact with skin fibroblasts. Due to the use of the compound that gives polymers such broad properties, new perspectives are opening up in the preparation and application of polyester materials.

The aim of this work was to determine the anisotropy of the electrophysical and mechanical properties of rubber reinforced with a hybrid filler CNTs&CB (carbon nanotubes and carbon black) as a function of CNT content and the technological parameters of the production process. A significant difference in electrical conductivity (σ) and dielectric permittivity (ε) in three perpendicular directions was found for CNT concentrations ranging from 0 to 0.007 in volume fraction. The highest values of σ and ε were observed in the calendering direction, with slightly lower values in the perpendicular direction. This effect was attributed to the orientation of polymer molecules and CNTs along the direction of movement during calendering, as well as the disruption of the cluster structure in the transverse direction. Although the calculated percolation threshold values of the investigated system differed slightly, a correlation was observed between the mechanical and electrophysical properties of CNTs&CB rubber. This correlation enables rubber products to be designed with optimal properties tailored to the desired direction.

The new actual scientific direction is in the development of different nanocomposites and the study of their medical–biological, physicochemical, and physicomechanical properties. One way to expand the functionality of nanocomposites and nanomaterials is to introduce carbon nanostructures into the polymer matrix. This study presents the properties of unsaturated polyester resins (Estromal, LERG S.A.) based on PET recyclate with multi-walled carbon nanotubes (MWCNTs): their mechanical and thermomechanical characteristics, resistance to ultraviolet radiation (UV-vis), and chemical resistance properties. The properties of the obtained materials were characterized using physical–chemical research methods. The changes in the properties of the composites for MWCNT content of 0.1, 0.3, and 0.5 wt % were determined. The results showed positive influences on the thermomechanical and mechanical properties of nanocomposites without significant deterioration of their gloss. Too much CNT added to the resin leads to heterogeneity of the composite structure.

Встановлено закономірності солюбілізації, таутомерних перетворень і зміни спектральних характеристик природного поліфенолу куркуміну в разі розчинення у водному середовищі катіонних ПАР — антисептиків етонію та декаметоксину залежно від їх концентрації в розчині. Показано, що в організованих міцелярних середовищах цих катіонних ПАР куркумін розчиняється в енольній формі, його розчинність збільшується на два порядки. Методом розчинності визначено величини констант зв’язування куркуміну з міцелами етонію (lgКзв = 4,39) та декаметоксину (lgКзв = 4,47). В доміцелярних розчинах довголанцюгового катіонного ПАР етонію до появи звичайних класичних міцел куркумін розчиняється у водному розчині переважно в кетонній формі і його концентрація зростає у 150 разів за рахунок утворення ним розчинних супрамолекулярних комплексів. На відміну від етонію, в доміцелярних розчинах коротколанцюгової катіонної ПАР декаметоксину практично не відбувається поліпшення розчинності та зсуву рівноваги кето-енольної таутомерії куркуміну. Виявлені закономірності мають вагоме наукове і прикладне значення для розробки лікарських препаратів на основі таких систем.

The sheet samples of thermally exfoliated graphite (TEG)–carbon nanotubes (CNT) composites (TEG-CNT-cs) were obtained by persulphate oxidation using chemical (CO) and electrochemical (anode) oxidation (ECAO). Electron microscopy reveals multi-layered structures of few-layer graphene nanosheets with folded and tubular-like fragments. The effective thermal diffusivity values were estimated by nonstationary photo-pyroelectric thermophysical characterization using the heat pulse and thermowave modulation methods. Comparison with other carbon (C-) based thermal management materials shows that TEG-CNT-cs exhibit thermal diffusivity, effusivity, and conductivity comparable with those of actual C–polymer- and C–C-composites. For TEG-CNT-cs, evaluated values of phonon mean free path (MFP) and relaxation time (RT) are in the ranges estimated for defective graphene. The values of diffusivity and effusivity, MFP, and RT are lower for denser TEG-CNT-cs obtained by ECAO and are higher for less dense TEG-CNT-cs obtained by CO. The obtained diffusivity and effusivity values designate TEG-CNT-cs as suitable thermal management materials.