Vol 65, No 3 (2023)

Free-radical copolymerization in bulk has afforded copolymers of N-vinylcaprolactam and N‑vinylimidazole (40–60 mol %). Thermosensitive behavior of aqueous solutions of the copolymers has been probed over wide pH range by means of dynamic and static light scattering as well as high-sensitivity differential scanning calorimetry. Three regions of thermally induced conformational behavior have been observed with the change in the medium pH from the alkaline to acidic: phase separation region (I), region of the conformational transition into the mesoglobules state (II), and region of stable molecular solution of the poly-electrolyte (III). Significant polyelectrolyte effects have been revealed for the salt-free solutions of the copolymers, reflected in the presence of fast and slow diffusion modes in the relaxation time distributions. Moderate increase in the ionic strength with the addition of the low-molecular salt has led to shielding of the polyelectrolyte effects, yet the pH-dependent regions of the conformational behavior have not been affected much. The existence of different types of the thermally induced conformational behavior depending on pH has been explained by the balance between hydrophobic interactions involving the N-vinylcaprolactam units and electrostatic interactions of the weakly basic N-vinylimidazole units.

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.

На основе фиброина, выделенного из коконов шелкопряда Bombyx mori, получены полифункциональные гемосорбенты для детоксикации крови и сыворотки крови. Проведены их физико-химические и морфологические исследования, изучены сорбционные свойства. Показано, что полученные гемосорбенты имеют высокую сорбционную активность. По сорбционной активности гемосорбент на основе фиброина, обработанного ультразвуком и сверхвысокочастотным облучением, превосходит серийно выпускаемый “Научно-производственным предприятием Биотех-М” гемосорбент ВНИИТУ-1 в колонке для гемосорбции “Гемос^®-КС”.

На основе пленок ПП, деформируемых в растворах ПВС по механизму крейзинга, получены новые полимер-полимерные нанокомпозиты. Методами АСМ, ДСК, гравиметрии, механических испытаний, измерения краевых углов смачивания и объемной пористости исследованы механизм деформации ПП в растворах ПВС, структура, состав, теплофизические свойства и смачиваемость композитов. Cтепень растяжения ПП и концентрация ПВС в растворе позволяют контролировать состав нанокомпозитов. Содержание ПВС может достигать 45 мас. % при степени вытяжки ПП 300%. После удаления летучей жидкой среды ПВС кристаллизуется в затрудненном пространстве мезопористой матрицы ПП с понижением степени кристалличности до 12‒14%. Введение гидрофильного компонента приводит к улучшению смачивания ПП, и краевой угол снижается с 98° для исходного ПП до 42° для композита. Гидрофилизацию с использованием явления крейзинга можно рассматривать как способ модификации, переработки и вторичного использования крупнотоннажного полимера.

Composite films of methyl cellulose and poly(urethane-imide) are obtained. At the poly(urethane-imide) content in the films above 50% phase separation of the polymers is observed. Using the methods of dynamic mechanical analysis and X-ray diffraction the structural organization of the films is studied, the temperatures of relaxation transitions are determined, and the mechanical characteristics of the composite films are investigated.

The composite samples with the graphene filler content of 0.014 to 0.05 wt % have been prepared via the in situ polymerization. The effect of the ultralow content of graphene on the set of wear-resistant and tribological properties of the synthesized composited based on ultra-high molecular weight polyethylene has been studied. Weas resistance of the synthesized materials under conditions of high-speed impact of a water-sand suspension, wear during microcutting and friction wear resistance have been investigated. Furthermore, the friction coefficient on steel has been determined. The introduction of graphene into the ultra-high molecular weight polyethylene has improved the resistance to abrasion during microcutting and has increased the wear resistance under the action of the water-sand suspension (the free abrasive wear).