Breaking Of Covalent Bonds Research Articles

Protonated molecular clusters: promoting molecular complexity

Abstract Molecules identified in Space display a diversity greater than ever, yet the mechanisms responsible for this complexity remain largely unknown. The extreme conditions faced by these molecules under astrophysical conditions raise several questions about their persistence and evolution. In this work, we explore the role of gas-phase protonated molecular dimers, which act both as protectors of existing molecules and as promotors in the emergence of new species. Experiments were conducted using the DIAM irradiation device on four protonated dimers of astrophysical interest, namely the pyridine, methanol, glycine pure dimers and the diglycine-glycine mixed dimer. Analysis of the observed relaxation channels following an energy deposition mimicking cosmic radiation reveals three main mechanisms of evaporation, covalent bond breaking, and unimolecular reaction. Focusing on the latter, our experiments combined with quantum chemical calculations of the relevant pathways shed new light onto the role of the protonation site on the reactants.

Pyrolysis characterization and kinetic analysis of typical coals in western China: effects of coal type, particle size and heating rate

ABSTRACT The three typical coals selected in this study (Shuangyi coal (SY), Hengsheng coal (HS) and Ningxia anthracite (NX)) are widely used in western China, but their pyrolysis characteristics have been less studied. In this study, based on the simultaneous thermal analysis-Fourier transform infrared spectroscopy (STA-FTIR) technique, the effects of different coal types, particle sizes and heating rates on the pyrolysis characteristics of coal powder were investigated. The results showed that the weight loss behaviors of different types of coals with different particle sizes varied, as influenced by the type of coal and heat transfer. When the particle size increased from 170 μm to 380 μm, the weight loss rate decreased by 2.95% and 24.45% for SY and NX coals while increased by 4.81% for HS coals; whereas for the maximum decomposition rate, both SY and HS coals showed an increasing tendency (increased by 2.76% and 9.32%), while NX coals decreased by 21.43%. The R2 of the three coal DTG curves fitted by subcurves was all 0.999, which proved that the nature of coal weight loss was the coupling effect of certain types of chemical reactions or covalent bond breakage. Real-time infrared spectroscopy was combined with covalent bonding to explore the major gas products and their influence by particle size. The activation energies at different temperatures were calculated by the Coats-Redfern method, in which the activation energies of the fast pyrolysis stage of HS coal were 1.68 and 2.75 times higher than those of the other two stages, 1.79 and 3.03 times higher than those of SY coal, and 1.99 and 1.11 times higher than those of NX coal, respectively.

Development of a 213Bi-Labeled Pyridyl Benzofuran for Targeted α-Therapy of Amyloid-β Aggregates.

Alzheimer disease is a neurodegenerative disorder with limited treatment options. It is characterized by the presence of several biomarkers, including amyloid-β aggregates, which lead to oxidative stress and neuronal decay. Targeted α-therapy (TAT) has been shown to be efficacious against metastatic cancer. TAT takes advantage of tumor-localized α-particle emission to break disease-associated covalent bonds while minimizing radiation dose to healthy tissues due to the short, micrometer-level, distances traveled. We hypothesized that TAT could be used to break covalent bonds within amyloid-β aggregates and facilitate natural plaque clearance mechanisms. Methods: We synthesized a 213Bi-chelate-linked benzofuran pyridyl derivative (BiBPy) and generated [213Bi]BiBPy, with a specific activity of 120.6 GBq/μg, dissociation constant of 11 ± 1.5 nM, and logP of 0.14 ± 0.03. Results: As the first step toward the validation of [213Bi]BiBPy as a TAT agent for the reduction of Alzheimer disease-associated amyloid-β, we showed that brain homogenates from APP/PS1 double-transgenic male mice (6-9 mo old) incubated with [213Bi]BiBPy exhibited a marked reduction in amyloid-β plaque concentration as measured using both enzyme-linked immunosorbent and Western blotting assays, with a half-maximal effective concentration of 3.72 kBq/pg. Conclusion: This [213Bi]BiBPy-concentration-dependent activity shows that TAT can reduce amyloid plaque concentration invitro and supports the development of targeting systems for invivo validations.

Evaluating the impact of filler size and filler content on the stiffness, strength, and toughness of polymer nanocomposites using coarse-grained molecular dynamics

Their great versatility makes polymer nanocomposites an important class of engineering materials. In order to gain detailed insights into the nanoscale mechanisms underlying their macroscopic mechanical properties, molecular dynamics (MD) simulations are a valuable tool to complement experimental studies. In this work, we modify the analytical potential functions of an efficient bead–spring model representing a generic polymer nanocomposite to account for the breaking of covalent bonds. We perform uniaxial tensile simulations of double-notched specimens and validate the model using experimental trends for overall stiffness, strength, and toughness. First, we study the effects of sample size, notch geometry, strain rate, temperature, and molar mass for the pure thermoplastic matrix material. Second, we analyze the influence of filler size and filler content on the mechanical behavior of the polymer nanocomposite. With this study, we show that in both the development of new materials and the optimization of established materials, it is possible to gain important preliminary insights into the effects of pertinent material characteristics with a simple MD setup, which can then be further refined by increasing the complexity of the material description and the boundary conditions.

Elucidating the photodegradation mechanism of octylisothiazolinone and dichlorooctylisothiazolinone in surface water: An in-depth comprehensive analysis

Octylisothiazolinone (OIT) and Dichlorooctylisothiazolinone (DCOIT), widely used antibacterial agents in coatings, have seen a sharp increase in use in response to the Coronavirus disease 2019 (Covid-19) pandemic, ultimately leading to their increase in the aquatic environment. However, their photodegradation process in surface water is still unclear. The purpose of this study is to investigate the photodegradation kinetics and mechanisms of OIT and DCOIT in natural water environments. Under simulated solar irradiation, they undergo direct photolysis in both natural freshwater and seawater mainly via their excited singlet states, while no self-sensitization photolysis was observed. The direct photolysis rate constants of OIT and DCOIT were 1.19 ± 0.07 and 0.57 ± 0.03 h−1, respectively. In addition, dissolved organic matter (DOM), NO3− and Cl− in natural waters did not contribute significantly to the photodegradation, and the light screening effect of DOM was identified as the main inhibiting factor. The photodegradation half-life of OIT was estimated to be 0.66 to 1.69 days, while the half-life of DCOIT was as high as 20.9 days during winter in surface water at 30°N latitude. Ring opening of the N-S bond and covalent bond breaking between CN are the main pathways for the photodegradation of OIT and DCOIT, which is verified by density-functional theory calculations. Ecological Structure Activity Relationships (ECOSAR) results indicate that OIT and DCOIT have “Very Toxic” biological toxicity, and the acute toxicity of their products is significantly reduced. It is noteworthy that the toxicity of the products of DCOIT is generally higher than that of OIT, and the chronic toxicity of most of the products is still above the “Toxic” level. Therefore, an in-depth understanding of the photodegradation mechanisms of OIT and DCOIT in aqueous environments is crucial for accurately assessing their ecological risks in natural water environments.

Molecular orbital breaking in photo-mediated organosilicon Schiff base ferroelectric crystals

Ferroelectric materials, whose electrical polarization can be switched under external stimuli, have been widely used in sensors, data storage, and energy conversion. Molecular orbital breaking can result in switchable structural and physical bistability in ferroelectric materials as traditional spatial symmetry breaking does. Differently, molecular orbital breaking interprets the phase transition mechanism from the perspective of electronics and sheds new light on manipulating the physical properties of ferroelectrics. Here, we synthesize a pair of organosilicon Schiff base ferroelectric crystals, (R)- and (S)-N-(3,5-di-tert-butylbenzylidene)-1-((triphenylsilyl)oxy)ethanamine, which show optically controlled phase transition accompanying the molecular orbital breaking. The molecular orbital breaking is manifested as the breaking and reformation of covalent bonds during the phase transition process, that is, the conversion between C = N and C–O in the enol form and C–N and C = O in the keto form. This process brings about photo-mediated bistability with multiple physical channels such as dielectric, second-harmonic generation, and ferroelectric polarization. This work further explores this newly developed mechanism of ferroelectric phase transition and highlights the significance of photo-mediated ferroelectric materials for photo-controlled smart devices and bio-sensors.

Macrophage-Inspired marine antifouling coating with dynamic surfaces based on regulation of dynamic covalent bonds

Macrophages can kill bacteria and viruses by releasing free radicals, which provides a possible approach to construct antifouling coatings with dynamic surfaces that release free radicals if the breaking of dynamic covalent bonds is precisely regulated. Herein, inspired by the defensive behavior of macrophages of releasing free radicals to kill bacteria and viruses, a marine antifouling coating composed of polyurethane incorporating dimethylglyoxime (PUx-DMG) is prepared by precise regulation of dynamic oxime-urethane covalent bonds. The obtained alkyl radical (R·) derived from the cleavage of the oxime-urethane bonds manages to effectively suppress the attachment of marine biofouling. Moreover, the intrinsic dynamic surface makes it difficult for biofouling to adhere and ultimately achieves sustainable antifouling property. Notably, the PU50-DMG coating not only presents efficient antibacterial and antialgae properties, but also prevents macroorganisms from settling in the sea for up to 4 months. This provides a pioneer broad-spectrum strategy to explore the marine antifouling coatings.

Near equivalence of polarizability and bond order flux metrics for describing covalent bond rearrangements.

Identification of the breaking point for the chemical bond is essential for our understanding of chemical reactivity. The current consensus is that a point of maximal electron delocalization along the bonding axis separates the different bonding regimes of reactants and products. This maximum transition point has been investigated previously through the total position spread and the bond-parallel components of the static polarizability tensor for describing covalent bond breaking. In this paper, we report that the first-order change of the Wiberg and Mayer bond index with respect to the reaction coordinate, the bond flux, is similarly maximized and is nearly equivalent with the bond breaking points determined by the bond-parallel polarizability. We investigate the similarites and differences between the two bonding metrics for breaking the nitrogen triple bond, twisting around the ethene double bond, and a set of prototypical reactions in the hydrogen combustion reaction network. The Wiberg-Mayer bond flux provides a simpler approach to calculating the point of bond dissociation and formation and can yield greater chemical insight through bond specific information for certain reactions where multiple bond changes are operative.

Cutting soft matter: scaling relations controlled by toughness, friction, and wear.

Cutting mechanics of soft solids is gaining rapid attention thanks to its promising benefits in material characterization and other applications. However, a full understanding of the physical phenomena is still missing, and several questions remain outstanding. E.g.: How can we directly and reliably measure toughness from cutting experiments? What is the role of blade sharpness? In this paper, we explore the simple problem of wire cutting, where blade sharpness is only defined by the wire radius. Through finite element analysis, we obtain a simple scaling relation between the wire radius and the steady-state cutting force per unit sample thickness. The cutting force is independent of the wire radius if the latter is below a transition length, while larger radii produce a linear force-radius correlation. The minimum cutting force, for small radii, is given by cleavage toughness, i.e., the surface energy required to break covalent bonds in the crack plane. The force-radius slope is instead given by the wear shear strength in the material. Via cutting experiments on polyacrylamide gels, we find that the magnitude of shear strength is close to the work of fracture of the material, i.e., the critical strain energy density required to break a pristine sample in uniaxial tension. The work of fracture characterizes the toughening contribution from the fracture process zone (FPZ), which adds to cleavage toughness. Our study provides two important messages, that answer the above questions: toughness can be estimated from wire-cutting experiments from the intercept of the force-radius linear correlation, as previously explored. However, as we discovered, this only estimates cleavage toughness. Additionally, the force-radius slope is correlated with the work of fracture, giving an estimation of the dissipative contributions from the FPZ.

Molecular Ionization Dissociation Induced by Interatomic Coulombic Decay in an ArCH_{4}-Electron Collision System.

Interatomic Coulombic decay (ICD) is a significant fragmentation mechanism observed in weakly bound systems. It has been widely accepted that ICD-induced molecular fragmentation occurs through a two-step process, involving ICD as the first step and dissociative-electron attachment (DEA) as the second step. In this study, we conducted a fragmentation experiment of ArCH_{4} by electron impact, utilizing the coincident detection of one electron and two ions. In addition to the well-known decay pathway that induces pure ionization of CH_{4}, we observed a new channel where ICD triggers the ionization dissociation of CH_{4}, resulting in the cleavage of the C-H bond and the formation of the CH_{3}^{+} and H ion pair. The high efficiency of this channel, as indicated by the relative yield of the Ar^{+}/CH_{3}^{+} ion pair, agrees with the theoretical prediction [L. S. Cederbaum, J. Phys. Chem. Lett. 11, 8964 (2020).JPCLCD1948-718510.1021/acs.jpclett.0c02259; Y. C. Chiang et al., Phys. Rev. A 100, 052701 (2019).PLRAAN2469-992610.1103/PhysRevA.100.052701]. These results suggest that ICD can directly break covalent bonds with high efficiency, bypassing the need for DEA. This finding introduces a novel approach to enhance the fragmentation efficiency of molecules containing covalent bonds, such as DNA backbone.

Molecular clips triggered on the active surface of liquid metals via oxygen capture at room temperature

Covalent bond breaking and reforming of molecules are the effective strategies to drive complex chemical reactions in clip chemistry. However, the harsh reaction conditions, complex reaction process, great energy consumption and high pollution have brought great obstacles to the previous clipping techniques. Herein, we propose a concept for molecules sustainable and directional clipping via oxygen capture at room temperature based on the special structures and interfacial properties of gallium-based liquid metals. As a proof-of-concept, we report the liquid metals of eGaIn, obtained by mixing of gallium with indium particles. The liquid phase transformation of eGaIn endowed them for an excellent active surface, which enabled spontaneously, rapidly, and directionally capturing oxygen from 1,3-butanediol molecules, and transformed into GaO(OH) semiconductor functional materials with a wide application potential. The oxygen-containing covalent bonds in 1,3-butanediol were randomly broken, including C–O and H–O, then multiple active groups were generated. After reconstruction, the active groups formed H2, carboxylates and carbon materials. These dispersed in 1,3-butanediol and endowed it with fluorescent properties under UV excitation. Particularly, liquid metals can be used as a basic tool for molecular directional clipping and obtaining specific functional materials. This finding refreshed our basic understanding of liquid metals, clip chemistry and molecules, led to easygoing practices of molecular weaving. It also has promising potential for future molecular engineering, life science, energy and environment, and biomedicine.

Mass balance accounting: Considerations for circular polymers

AbstractWhile plastic packaging and products have greatly benefitted civilization, the current and historical approaches to design, use, and end‐of‐life management have resulted in significant challenges, particularly in recovering and retaining the economic value of the materials and preventing plastic pollution. The dominant route for recycling plastic in the United States and elsewhere has been mechanical recycling, which is effective for select polymer types and package designs and has potential for growth. However, several regulatory, technical, and economic challenges will ultimately cap the fraction of plastic waste recovered by mechanical recycling technologies, and as a result, chemical recycling―processes that either break covalent bonds or otherwise exploit fundamental chemical processes to return molecules to early or mid‐stage chemical production―has great appeal, especially for plastic products most challenging for mechanical recycling. Due to the nature of some chemical recycling technologies, specifically that molecules derived from chemically recycled polymers become indistinguishable from primary feedstocks and thus not traceable or measurable in the process, the mass balance (MB) accounting chain of custody model has been proposed as a tool to track, trace, and certify circular polymers. While MB certification standards have an extensive history in other commodity sectors, they have only recently been considered in the polymers sector in part due to recent technology advances and incentives to expand chemical recycling. Here we discuss the roll of MB in polymer circularity, including controversial aspects, and provide technical examples to describe its potential applicability. We further provide recommendations for the effective use of MB to certify circular polymers.This article is categorized under: Climate and Environment > Pollution Prevention Climate and Environment > Circular Economy Emerging Technologies > Materials

Novel slow-release nanohybrid from zinc hydroxysalt intercalated with dicamba herbicide

Dicamba was intercalated by co-precipitation into a zinc-layered hydroxide salt (LHS) to create a slow-release nanohybrid weed control without leaching. The X-Ray Powder Diffractometry (XRPD) patterns of the LHS intercalated with dicamba showed a basal spacing of 20.48 Å and 26.10 Å, confirming its allocation as a monolayer and bilayer interdigitated arrangement, respectively. The Fourier Transformant Infrared (FTIR) spectrum showed bands typical of dicamba and provided information about its bridging bidentate coordination to the matrix layer. The thermogravimetric analysis (TGA) estimated the compound's formula as Zn5(OH)8(dicamba)2·4.14H2O. The thermal stability of the LHS/dicamba system, the stages of mass loss, the characterization of the compounds released in the pyrolysis, the activation energy (Ea), and the kinetics were all analyzed. The average activation energy for decomposition of intercalated dicamba indicates that the thermal degradation occurred with the breakage of covalent bonds. Controlled release of dicamba from its nanohybrid in water was observed for 962 h (40 days). The pseudo-second-order model described the release process satisfactorily from its linear fitting, suggesting intraparticle diffusion or surface diffusion control. In summary, the intercalation of dicamba in the zinc LHS produced a slow-release material that can aid in weed control.

Transformation of K2Sb8Q13 and KSb5Q8 Bulk Crystals to Sb2Q3 (Q = S, Se) Nanofibers by Acid-Base Solution Chemistry.

The ability to manipulate crystal structures using kinetic control is of broad interest because it enables the design of materials with structures, compositions, and morphologies that may otherwise be unattainable. Herein, we report the low-temperature structural transformation of bulk inorganic crystals driven by hard-soft acid-base (HSAB) chemistry. We show that the three-dimensional framework K2Sb8Q13 and layered KSb5Q8 (Q = S, Se, and Se/S solid solutions) compounds transform to one-dimensional Sb2Q3 nano/microfibers in N2H4·H2O solution by releasing Q2- and K+ ions. At 100 °C and ambient pressure, a transformation process takes place that leads to significant structural changes in the materials, including the formation and breakage of covalent bonds between Sb and Q. Despite the insolubility of the starting crystals in N2H4·H2O under the given conditions, the mechanism of this transformation can be rationalized by applying the HSAB principle. By adjusting factors such as the reactants' acid/base properties, temperature, and pressure, the process can be controlled, allowing for the achievement of a wide range of optical band gaps (ranging from 1.14 to 1.59 eV) while maintaining the solid solution nature of the anion sublattice in the Sb2Q3 nanofibers.

Repartitioned Brillouin-Wigner perturbation theory with a size-consistent second-order correlation energy.

Second-order Møller-Plesset perturbation theory (MP2) often breaks down catastrophically in small-gap systems, leaving much to be desired in its performance for myriad chemical applications such as noncovalent interactions, thermochemistry, and dative bonding in transition metal complexes. This divergence problem has reignited interest in Brillouin-Wigner perturbation theory (BWPT), which is regular at all orders but lacks size consistency and extensivity, severely limiting its application to chemistry. In this work, we propose an alternative partitioning of the Hamiltonian that leads to a regular BWPT perturbation series that, through the second order, is size-extensive, size-consistent (provided its Hartree-Fock reference is also), and orbital invariant. Our second-order size-consistent Brillouin-Wigner (BW-s2) approach can describe the exact dissociation limit of H2 in a minimal basis set, regardless of the spin polarization of the reference orbitals. More broadly, we find that BW-s2 offers improvements relative to MP2 for covalent bond breaking, noncovalent interaction energies, and metal/organic reaction energies, although rivaling coupled-cluster with single and double substitutions for thermochemical properties.

Protein posttranslational modifications in health and diseases: Functions, regulatory mechanisms, and therapeutic implications.

Protein posttranslational modifications (PTMs) refer to the breaking or generation of covalent bonds on the backbones or amino acid side chains of proteins and expand the diversity of proteins, which provides the basis for the emergence of organismal complexity. To date, more than 650 types of protein modifications, such as the most well-known phosphorylation, ubiquitination, glycosylation, methylation, SUMOylation, short-chain and long-chain acylation modifications, redox modifications, and irreversible modifications, have been described, and the inventory is still increasing. By changing the protein conformation, localization, activity, stability, charges, and interactions with other biomolecules, PTMs ultimately alter the phenotypes and biological processes of cells. The homeostasis of protein modifications is important to human health. Abnormal PTMs may cause changes in protein properties and loss of protein functions, which are closely related to the occurrence and development of various diseases. In this review, we systematically introduce the characteristics, regulatory mechanisms, and functions of various PTMs in health and diseases. In addition, the therapeutic prospects in various diseases by targeting PTMs and associated regulatory enzymes are also summarized. This work will deepen the understanding of protein modifications in health and diseases and promote the discovery of diagnostic and prognostic markers and drug targets for diseases.

Coal/NH3 interactions during co-pyrolysis and their effects on the char reactivity for NO-reduction: A ReaxFF MD study

In this work, the interactions between NH3 and coal during co-pyrolysis and their influences on char structure and char reactivity for NO reduction are investigated using reactive molecular dynamic (ReaxFF MD) simulations, revealing that coal promotes the thermal decomposition of NH3 because it provides H radicals to attack the N-H bonds in NH3. The primary pyrolysis reactions (thermal breaking of weak covalent bonds) of coal are inhibited by NH3·NH3 also influences the secondary reactions in coal pyrolysis through two aspects: (1) promotes tar cracking to generate gas, and (2) inhibits the polymerization of tar to form char. Compared with coal pyrolysis, the H/C ratio of char and number of O and N atoms in char decrease more slowly during coal/NH3 co-pyrolysis. However, NH3 has little influence on the release of H2S. The effect of NH3 on the physicochemical properties of the char is then analyzed. The oxygen atoms are present mainly as hydroxyl, ether, and carbonyl forms, and the nitrogen atoms are present mainly as cyanide and amino forms in both coal pyrolysis char and coal/NH3 co-pyrolysis char. The coal/NH3 co-pyrolysis char has lower helium density, lower graphitization degree, and larger pores compared with coal pyrolysis char. Finally, the reactivity of coal pyrolysis char and coal/NH3 co-pyrolysis char for NO reduction are examined. The coal/NH3 co-pyrolysis char is more conducive to NO chemisorption and N2 generation. Using a first-order kinetics model, the activation energy of NO reduction reactions on coal pyrolysis char and coal/NH3 co-pyrolysis char are determined as 180 and 123 kJ/mol, respectively.

Covalent-like bondings and abnormal formation of ferroelectric structures in binary ionic salts.

In the Mooser-Pearson diagram, binary ionic compoundss form into nonpolar symmetrical structures with high coordination numbers, while wurtzite structures should appear in the covalent region. Their tetrahedral bonding configurations break the inversion symmetry, with polarizations almost unswitchable due to the high barriers of abrupt breaking and reformation of covalent bonds. Here, through first-principles calculations, we find some exceptional cases of highly ionic ferroelectric binary salts such as lithium halides, which may form into wurtzite structures with covalent-like sp3 bondings, and the origin of these abnormal formations is clarified. Their high polarizations induced by symmetry breaking are switchable, with much smoother switching pathway refrained from abrupt bond breaking due to the long-range feature of Coulomb interactions. These covalent-like ionic bondings do reduce not only their ferroelectric switching barriers but also the phase transition barriers between polar and nonpolar phases, rendering high performance in applications such as nonvolatile memory and energy storage.

Mechanistic insights into the adsorption of endocrine disruptors onto polystyrene microplastics in water

Microplastics and endocrine disruptors (EDs) are contaminants of emerging concerns and ubiquitously present in aquatic ecosystems, establishing interactions that still are the subject of investigation due to their implications in the cotransport of pollutants. Then, we conducted mechanistic studies based on state-of-art computational chemistry methods to quantitatively understand the interaction mechanisms whereby polystyrene micro or nanoplastics (PS-MPs) interact with representative classes of EDs in water (Ethynylestradiol, Estradiol, and Bisphenol A). The results showed that PS-MPs increase their charge distribution when forming microparticles in water, giving a permanent dipole that explains their increasing solubility in aqueous conditions. In agreement with experimental assessments, the PS-MPs favorably adsorb EDs with adsorption energies larger than 15 kcal/mol, even with comparable stability to nanostructured materials for adsorption, removal, and/or analysis of pollutants. The adsorption occurs via physisorption without covalent binding, bond breaking, or structural preparation energies, where the molecular structure of EDs can favor inner or outer surface adsorption depending on the molecular structure of the adsorbates. A balanced contribution of dispersion and electrostatic stabilizing effects determines the interaction mechanisms, accounting for a whole contribution of 88–90%. The electrostatic contribution emerges from the favorable alignment of the PS-MPs and EDs dipoles upon interaction due to the mild charge transfer between them in solution. In contrast, the dispersion contribution emerges from electron-electron interactions due to the permanent dipoles in adsorbates and adsorbents. Furthermore, thermochemical analyses clarify the role of temperature and pressure effects on the relative adsorption stability among EDs in aquatic environments. Therefore, modeling the adsorption process contributes to new knowledge on the sorption properties of PS-MPs, providing a mechanistic basis to understand the cotransport of pollutants in water environments and their impacts on environmental pollution.

Simulation of the processes of plasma modification and vacuum metallization of polymer materials by the method of molecular dynamics

The article presents the results of the development of molecular dynamics models of modifications of polypropylene (PP) material in the plasma of a radio-frequency (RF) discharge and a copper coating deposit by magnetron sputtering on the surface of a polyethylene (PE) material. The model of the RF plasma modification process describes changes in the surface layers of the PP material upon interaction with low-energy plasma ions: the nature of the breaking of covalent bonds in macromolecules, the chemical composition of sputtered particles, and changes in the ordering of the supramolecular structure. The model of the vacuum metallization process describes the processes of the introduction of metal atoms into the polymer structure, the change in the conformation of macromolecules, the formation of macroradicals with uncompensated chemical bonds, and the formation of an interfacial layer between the polymer and the metal coating.