The results of the comparison of two big chemical databases PubChem-Compound (general chemical information) and Aurora Fine Chemical (commercially available compounds) are presented. Each database contains about 115M records. The performed comparison shows that about 50% of the structures in these databases are identical while the rest are unique to each database, which is unexpected for such large samples. The PubChem compounds database contains many structures that are unstable at room temperature. For a more detailed comparison, the chemical structures are decomposed into circular fragments with a radius of up to 3 chemical bonds. It was found that the PubChem compounds database contains 1.5 times more fragments, than AFC. It is explained that the average size of a chemical structure in PubChem Compounds is larger than in Aurora Fine Chemicals. We also find that among the 30 most distributed fragments, 28 are common to both databases. Analysis of the unique fragments allowed us to find structures that are poorly represented in each of the databases. These are triple-bonded compounds in the PubChem Compounds database and organosilicon compounds in the Aurora Fine Chemicals database. Our study provides important information for the development of in silico engineering approaches for new polymers based on virtual synthesis from simple chemical fragments.

A description of the MULTICOMP package is presented. The package was developed for multi-level modeling of polymeric materials and nanocomposites. The package includes a graphical user interface for material model construction, implementation of the modeling process, and analysis of the obtained results. For professional use, MULTICOMP supports the client-server architecture, which allows the transfer of resource-intensive calculations to remote computer clusters. As an example, the structure of the new Permeability module, designed to evaluate the gas permeability of thermoplastic polymers, is described. The new Nanoobjects module for creating models of nanoparticles and surfaces is also described. The results of using MULTICOMP to evaluate gas permeability, mechanical and thermal conductivity properties, and the performance of the package on various computing platforms are discussed.

Поиск способов управления структурой волокон прекурсоров на основе полиакрилонитрила является ключом к модификации свойств углеродных волокон. В публикации обсуждаются результаты мезомасштабного моделирования процессов структурообразования в смеси полиакрилонитрила, диметилсульфоксида и воды (хороший и плохой растворители для полимера). Выбор состава системы был сделан на основе представлений о составе волокон прекурсоров на поздних стадиях формирования в условиях коагуляционной ванны. Все расчеты выполнены с использованием динамической теории функционала плотности. Разработанная модель позволяет учитывать влияние изменения состава системы, влияния наполнителя в виде углеродных нанотрубок, температуры и сдвигового потока. Полученные результаты показывают, что посредством варьирования количества воды в системе (что определяется составом коагуляционной ванны) и введения углеродного наполнителя можно значительно изменять структуру полимера.

A method for assessing the synthesis complexity of in silico designed polymers using the modified Synthetic Accessibility Score Index is presented. This index is calculated by decomposing a chemical structure into smaller fragments and evaluating their contribution to the overall score. Also discussed are the data sources for these estimates, ways to overcome ambiguity in the representation of the smallest repeating unit of polymers, and the problem of evaluating the stability of chemical structures stored in machine- generated databases.

Bulk radical copolymerisation of N-vinylcaprolactam (VCL) and N-vinylimidazole (VI) is studied experimentally and theoretically. It is shown that the copolymer composition is maintained up to high comonomer conversions. This is explained by a constant ratio of concentrations of comonomers in the reaction zone. The copolymers obtained show thermally induced conformational behaviour. In an aqueous medium above 60 degrees C, they can form compact globular structures with a hydrophobic core of VCL monomer units covered by a hydrophilic corona of VI monomer units, which allows them to be considered as a basis for thermally switchable functional nanostructures.

Silica-supported chromium oxide catalysts, also named Phillips chromium catalysts (PCCs), provide more than half of the world’s production of high- and medium-density polyethylenes. PCCs are usually prepared in the Cr(VI)/SiO2 form, which is subjected to reductive activation. It has been explicitly proven that CO reduces Cr(VI) to Cr(II) species that initiate ethylene polymerization; ethylene activates Cr(VI) sites as well, but the nature of the catalytic species is complicated by the presence of the ethylene oxidation products. It is widely accepted that the catalytic species are of a Cr(III)–alkyl nature, but this common assumption faces the challenge of “extra” hydrogen: the formation of similar species under the action of even-electron reducing agents requires an additional H atom. Relatively recently, it was found that saturated hydrocarbons can also activate CrOx/SiO2, and alkyl fragments turn out to be bonded with a polyethylene chain. In recent years, there have been numerous experimental and theoretical studies of the structure and chemistry of PCCs at the different stages of preparation and activation. The use of modern spectral methods (such as extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES), and others); operando IR, UV–vis, EPR, and XAS spectroscopies; and theoretical approaches (DFT modeling, machine learning) clarified many essential aspects of the mechanisms of CrOx/SiO2 activation and catalytic behavior. Overall, the Cosse–Arlman mechanism of polymerization on Cr(III)–alkyl centers is confirmed in many works, but its theoretical support required the development of nontrivial and contentious mechanistic concepts of Cr(VI)/SiO2 or Cr(II)/SiO2 activation. On the other hand, conflicting experimental data continue to be obtained, and certain mechanistic concepts are being developed with the use of outdated models. Strictly speaking, the main question of what type of catalytic species, Cr(II), Cr(III), or Cr(IV), comes into polymerization still has not received an unambiguous answer. The role of the chemical nature of the support—through the prism of the nature, geometry, and distribution of the active sites—is also not clear in depth. In the present review, we endeavored to summarize and discuss the recent studies in the field of the preparation, activation, and action of PCCs, with a focus on existing contradictions in the interpretation of the experimental and theoretical results.

A method for controlling the distribution and orientation of 2D fillers in the copolymer matrix is presented.

The key to the modification of the properties of carbon fibers is to understand how to control the structure of polyacrylonitrile-based precursors. Results of a mesoscale modeling of the structure formation processes in a mixture of polyacrylonitrile, dimethyl sulfoxide, and water (good and poor solvents for polymers) are reported. The system′s composition is chosen using the composition of precursor fibers at the later formation stages under coagulation bath conditions. All calculations are performed using the dynamic density functional theory. The proposed model considers effects caused by changes in the system composition, carbon nanotube filler, temperature, and shear flow. It is shown that the polymer structure can be significantly changed by varying the amount of water in the system (determined by the coagulation bath composition) and by introducing a carbon filler.

We present a mesoscale model and the simulation results of a system composed of polyacrylonitrile (PAN), carbon nanotubes (CNTs), and a mixed solvent of dimethylsulfoxide (DMSO) and water. The model describes a fragment of a nascent PAN/CNT composite fiber during coagulation. This process represents one of the stages in the production of PAN composite fibers, which are considered as precursors for carbon fibers with improved properties. All calculations are based on dynamic density functional theory. The results obtained show that the greatest structural heterogeneity of the system is observed when water dominates in the composition of the mixed solvent, which is identified with the conditions of a non-solvent coagulation bath. The model also predicts that the introduction of CNTs can lead to an increase in structural heterogeneity in the polymer matrix with increasing water content in the system. In addition, it is shown that the presence of a surface modifier on the CNT surface, which increases the affinity of the filler to the polymer, can sufficiently reduce the inhomogeneity of the nascent fiber structure.

The dependence of the adhesion energy of the polyacrylonitrile oligomeric chain on the surfaces of carbon nanoparticles such as carbon nanotubes and graphene is studied in the framework of full atomistic molecular mechanics simulation using the polymer consistent force field and the open part of the condensed-phase optimized molecular potentials for atomistic simulation studies force field. The length of the polyacrylonitrile oligomer chain, the number of layers in the graphene nanoparticle, the diameter of the carbon nanotube, and the type and density of the modifier molecules on the surface of the graphene are the main parameters of the calculations. The graphene nanoparticle is taken as a limiting case corresponding to the large-diameter carbon nanotube. N-(2-aminoethyl) carbamoyl, nitrocyclohexane, benzamide, and dinitrobiphenyl are selected as surface modifiers. It is shown that with an increase in the number of layers and diameter of carbon nanotubes, the adhesion energy of the polyacrylonitrile oligomer chain increases, which allows us to consider multiwalled carbon nanotube with large diameters as a preferred filler for polyacrylonitrile. The estimates obtained also show that when surface modifiers are used, it is possible to increase the adhesion energy of polyacrylonitrile only in the case of low surface modifier densities.

The paper discusses the development of a multiscale computational model for predicting the permeability of multilayer protective films consisting of multiple polymeric and hybrid layers containing clay minerals as fillers. The presented approach combines three levels of computation: continuous, full atomic, and quantitative structure–property correlations (QSPR). Oxygen and water are chosen as penetrant molecules. The main predictions are made using the continuum model, which takes into account the real scales of films and nanoparticles. It is shown that reliable predictions of the permeability coefficients can be obtained for oxygen molecules, which is not always possible for water. The latter requires the refinement of existing QSPR methods and interatomic interaction potentials for the atomistic level of calculations. Nevertheless, we show that the maximum effect on permeability reduction from the addition of clay fillers to the hybrid layer can be achieved by using nanoparticles with large aspect ratios and a high degree of orientational order. In addition, the use of the hybrid layer should be combined with the use of polymer layers with minimal oxygen and water permeability. The constructed model can be used to improve the properties of protective coatings for food and drug storage and to regulate the gas permeability of polymeric materials.

THz radiation induces a variety of processes in cells and has attracted the attention of researchers in recent decades. Here, data on the effects of high-intensity terahertz (THz) radiation on human directly reprogrammed neural progenitor cells (drNPCs) and on neuroblastoma cells (SK-N-BE (2)) were obtained for the first time. The results demonstrated that the exposure of non-tumor and tumor cells to broadband (0.1–3 THz) THz pulses with the intensity of 21 GW/cm2 and the electric field strength of 2.8 MV/cm for 30 min induced neither a noticeable genotoxic effect nor a statistically significant change in the proliferative activity and cell differentiation. It was also shown that the combined effect of THz radiation and salinomycin, a promising antitumor agent, on neuroblastoma cells did not enhance the genotoxic effect of this antibiotic. However, further studies involving chemotherapy drugs and other exposure parameters are warranted to introduce this new concept into anti-tumor clinical practice and to enhance the efficacy of the existing approaches.

Polyacrylonitrile (PAN) is widely used as a raw material for the production of high-modulus carbon fibers, the internal structure of which is directly affected by the spinning of the precursor. Although PAN fibers have been studied for a long time, the formation of their internal structure has not been sufficiently investigated theoretically. This is due to the large number of stages in the process and the parameters controlling them. In this study, we present a mesoscale model describing the evolution of nascent PAN fibers during the coagulation. It is constructed within the framework of a mesoscale dynamic density functional theory. We use the model to study the influence of a combined solvent of dimethyl sulfoxide (DMSO, a good solvent) and water (a non-solvent) on the microstructure of the fibers. A porous structure of PAN is formed as a result of the microphase separation of the polymer and the residual combined solvent at a high water content in the system. The model shows that one of the possible ways to obtain the homogeneous fiber structure is to slow down the coagulation by increasing the amount of good solvent in the system. This result is in agreement with the existing experimental data and confirms the efficiency of the presented model.

This publication continues the cycle of our work aimed at improving the methodology for constructing mesoscale models of network polymers and characterizing their physical properties. As the object of study, the epoxy resin of bisphenol A, diglycidyl ether, and a tricarboxylic fatty acid hardener was chosen. Its structure is the result of three parallel reactions. For their correct reproduction, an algorithm was proposed, which allows to take into account the peculiarities of the relationship of all ongoing processes. The system model was constructed by mapping the chemical structure of the monomers onto an equivalent mesoscale representation. It was used to study the relationship between the structure and mechanical properties of feeding networks as a function of the ratio of volume fractions of comonomers in the initial reaction mixture. All calculations were performed within the reaction version of the dissipative particle dynamics method. The structure of polymer networks in the constructed samples was characterized by topological analysis. The study of mechanical properties was carried out by constructing the "stress-strain" dependencies. The results obtained show a good correlation between the density of the load-bearing chains and the mechanical properties of the resulting networks. It is shown that the material samples with the highest degree of transformation and the density of the number of load-bearing chains have the highest stiffness.

Composites of synthetic bone mineral substitutes (BMS) and biodegradable polyesters are of particular interest for bone surgery and orthopedics. Manufacturing of composite scaffolds commonly uses mixing of the BMS with polymer melts. Melt processing requires a high homogeneity of the mixing, and is complicated by BMS-promoted thermal degradation of polymers. In our work, poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) composites reinforced by commercial β-tricalcium phosphate (βTCP) or synthesized carbonated hydroxyapatite with hexagonal and plate-like crystallite shapes (hCAp and pCAp, respectively) were fabricated using injection molding. pCAp-based composites showed advanced mechanical and thermal characteristics, and the best set of mechanical characteristics was observed for the PLLA-based composite containing 25 wt% of pCAp. To achieve compatibility of polyesters and pCAp, reactive block copolymers of PLLA or PCL with poly(tert-butyl ethylene phosphate) (C1 and C2, respectively) were introduced to the composite. The formation of a polyester-b-poly(ethylene phosphoric acid) (PEPA) compatibilizer during composite preparation, followed by chemical binding of PEPA with pCAp, have been proved experimentally. The presence of 5 wt% of the compatibilizer provided deeper homogenization of the composite, resulting in a marked increase in strength and moduli as well as a more pronounced nucleation effect during isothermal crystallization. The use of C1 increased the thermal stability of the PLLA-based composite, containing 25 wt% of pCAp. In view of positive impacts of polyester-b-PEPA on composite homogeneity, mechanical characteristics, and thermal stability, polyester-b-PEPA will find application in the further development of composite materials for bone surgery and orthopedics.

We present a theoretical approach for the in silico generation of new polymer structures for the systematic search for new materials with advanced properties. It is based on Bicerano’s Regression Model (RM), which uses the structure of the smallest repeating unit (SRU) for fast and adequate prediction of polymer properties. We have developed the programs (a) GenStruc, for generating the new polymer SRUs using the enumeration and Monte Carlo algorithms, and (b) PolyPred, for predicting properties for a given input polymer as well as for multiple structures stored in the database files. The structure database from the original Bicerano publication is used to create databases of backbones and pendant groups. A database of 5,142,153 unique SRUs is generated using the scaffold-based combinatorial method. We show that using only known backbones of the polymer SRU and varying the pendant groups can significantly improve the predicted extreme values of polymer properties. Analysis of the obtained results for the dielectric constant and refractive index shows that the values of the dielectric constant are higher for polyhydrazides than for polyhydroxylamines. The high value predicted for the refractive index of polythiophene and its derivatives is in agreement with the experimental data.

A novel graded-HOMO-level hole transport polymer (g-HTP) is proposed for the first time with spiro-polyfluorene (sPF) as the main chain and the three hole-transporting moieties triphenyl amine (TPA), carbazole (Cz), and N,N '-dicarbazolyl-3,5-benzene (mCP) as side chains for effective hole injection across the large barrier 1.4 eV into the green-emission core-shell quantum dot (QD) CdSe/ZnS emission layer in inverted QD light-emitting diode (i-QLED): ITO/ZnO/QD/HTP/MoO3/Al, in which both oleophilic ligands (OA and TOP) in the QD are partially removed from QD surface by annealing at 270 degrees C for preventing dissolution by solvent in subsequent coating of hole transport material (HTM) solutions atop and also improving electron and hole mobilities, especially the former. The proposed g-HTP with various m:n mole ratios of mCP to TPA/Cz moieties along with various reported HTMs (PVK, Poly-TPD and TFB) are investigated. Among them, the proposed g-HTP with the comonomer mole ratio 1:1 gives the best performance eta(max) 36.1 cd A(-1) and B-max 208 600 cd m(-2), which is the highest performance among the reported i-QLEDs with single hole-transport layer ever documented. In addition, its efficiency roll off is low from 35.8 cd A(-1) at 10 000 cd m(-2) to 31.1 cd A(-1) at 100 000 cd m(-2).

The current study is focused on the preparation of Mo-10 vol%La2O3 and Mo-10 vol% La2Zr2O7 composite powders via low- and high-energy ball milling approaches as potential candidates for near-future high-temperature structural applications. The mechanical milling parameters play a critical role on the final powder's microstructure. When using the high-energy milling mode (using 800 rpm, ball-to-powder ratio (BPR) 100: 6), the homogeneous powder agglomerates are formed with refined laminated microstructure and more uniform ceramic phase distribution in both Mo-La2O3 and Mo-La2Zr2O7 systems compared to the powders produced by means of the low-energy milling mode (using 350 rpm, BPR 100: 6), where inhomogeneous powder mixture with less embedding of ceramic phases into Mo agglomerates was obtained. This study also focuses on the evaluation of high-temperature phase and microstructural stability of the produced composite powders treated at the temperature of 1300 degrees C under the different gaseous environments, including ambient, inert and reducing atmospheres. The Mo-10 vol% La2Zr2O7 composite powder exhibited better thermal stability during the high-temperature exposure in all tested atmospheres in comparison with the Mo-La2O3 composite powder, since it revealed less intensive formation of the intermediate phases, such as lanthanum oxymolybdates. Therefore, the Mo-10 vol%La2Zr2O7 composite powder was used further for consolidation by means of spark plasma sintering at 1600 degrees C. The successful production of Mo-La2Zr2O7 composite with homogeneous distribution of ceramic phase, the grain size about of 5 mu m, and hardness of 3.4 GPa was not reported so far.