polar groups
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2022 ◽  
Vol 906 ◽  
pp. 85-92
Author(s):  
Tatyana A. Matseevich ◽  
Andrey A. Askadskii

The method for estimating the influence of polar groups on the temperature of the onset of the intense thermal degradation of polymers under heating is proposed. This estimate is based on the equation for calculating this value for the entire repeating link proposed earlier [1-4]. The method is computerized and is included as an integral part of the computer program "Cascade" (INEOS RAS). The calculated estimation is carried out for one of the structures of the rejected cycloaliphatic epoxy resin. The most "weak" group was the group –CO–. The temperature of the onset of intensive thermal degradation of this group is 547 K.


2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Michael Ioelovich

In this research, the structural characteristics, specific surface area, sorption of water vapor, and wetting enthalpy of various polysaccharides (cellulose, hemicelluloses, starch, pectin, chitin, and chitosan) have been studied. It was confirmed that crystallites are inaccessible for water, and therefore water molecules can interact only with polar groups in noncrystalline (amorphous) domains of biopolymers. The isotherms of water vapor sorption for various polysaccharides had sigmoid shapes, which can be explained by the absorption of water molecules in heterogeneous amorphous domains having clusters with different packing densities. The method of contributions of polar groups to sorption of water molecules was used, which allowed to derivate a simple calculating equation to describe the shape of sorption isotherms. The wetting of biopolymers with water was accompanied by a high exothermic thermal effect, in direct proportion to the amorphicity degree. The sorption values and wetting enthalpies of amorphous domains of biopolymers were calculated, which allowed to find the hydrophilicity index and compare the hydrophilicity of the various polysaccharides.


Author(s):  
Raffaele Ciardiello ◽  
Domenico D’Angelo ◽  
Laura Cagna ◽  
Alessandro Croce ◽  
Davide Salvatore Paolino

Plasma treatment has been used in recent years to activate the surfaces of adhesive substrates and thus as an adhesion promoter between adhesive and substrates. The use of plasma treatments is widely adopted in the automotive industries especially for polymers that present low surface energy, such as polypropylene. In this work, polypropylene substrates used in the automotive industries have been treated with two different techniques: vacuum and atmospheric plasma. Then, polyurethane and methacrylate adhesives have been used to bond single lap joints (SLJs). Typically, these two adhesives cannot bond polypropylene substrates without surface treatments. An experimental plan has been designed to investigate the process parameters that can increase the functional polar groups (FPGs) maximizing the adhesion strength. Besides the types of plasma, two different gas carriers (air and nitrogen) and different treatment times have been investigated. The substrates, treated and not treated, have been assessed through scanning electron microscopy, energy-dispersive X-ray analysis, and Fourier-transform infrared spectroscopy to quantitatively assess the increment of FPGs after the different treatments. The experimental plan shows that the atmospheric plasma can improve the surface of the substrates by using a smaller time. Mechanical tests on SLJs show that methacrylate and polyurethane cannot bond polypropylene substrates without the plasma treatment. On the other hand, the treated substrates can form a strong bonding with the adhesive since all SLJs exhibit a substrate failure. Mechanical tests have been also carried out after three different aging cycles showing that the adopted plasma treatment is not affected by the aging cycles.


Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 206
Author(s):  
Mariia Nesterkina ◽  
Serhii Smola ◽  
Nataliya Rusakova ◽  
Iryna Kravchenko

Hydrazones based on mono- and bicyclic terpenoids (verbenone, menthone and carvone) have been investigated in vitro as potential biomembrane penetration enhancers. In this regard, liposomes composed of lecithin or cardiolipin as phospholipid phase components with incorporated fluorescence probes have been prepared using the thin-film ultrasonic dispersion method. The mean particle size of the obtained liposomes, established using laser diffraction, was found to be 583 ± 0.95 nm, allowing us to categorize them as multilamellar vesicles (MLVs) according to their morphology. Pursuant to fluorescence analysis, we may assume a reduction in microviscosity and, consequently, a decrease in the packing density of lecithin and cardiolipin lipids to be the major mechanism of action for terpenoid hydrazones 1–15. In order to determine the molecular organization of the lipid matrix, lipids were isolated from rat strata cornea (SCs) and their interaction with tested compounds was studied by means of Fourier transform infrared spectroscopy. FT-IR examination suggested that these hydrazones fluidized the SC lipids via the disruption of the hydrogen-bonded network formed by polar groups of SC constituents. The relationship between the structure of terpenoid hydrazones and their ability to enhance biomembrane penetration is discussed.


Author(s):  
Marina S. Potarykina

All police officers go through the process of professional selection and must be recommended by psychologists for service. However, information about aggressive and violent behaviour and other illegal actions of police officers regularly appears in the media. For this purpose, we have developed a questionnaire for identifying aggressive and violent tendencies of police officers. As a basis for the proposed research methodology, the psycho-dynamically oriented personality questionnaire (POPQ) "Resource" was used, based on the self-structural test of Günter Ammon. Aggression within the framework of this methodological approach is understood from the point of view of the subject's active attitude to the surrounding world rather than from the point of view of causing harm or damage to living organisms. The author's methodology was created in several stages – selection of statements to which the polar groups of employees responded reliably (p < 0.05), assessment of the discriminative ability of these statements and their internal consistency, calculation of the main psychometric characteristics, testing of the scale on an independent sample of police officers. The results of evaluating the validity and reliability of the questionnaire scale are presented in the study. The diagnostic tools are aimed at identifying the latent propensity of a police officer to illegitimate violence.


Author(s):  
Sophia Pavlenko ◽  
Daniil E Larin ◽  
Elena Nikolaevna Govorun

Abstract Thermoresponsive polymers are usually characterized by a locally amphiphilic chain structure and their self-assembly in solution is controlled, in particular, by the surface activity of the monomer units or side chains. We theoretically study the condensed state of a single diblock copolymer molecule consisting of a hydrophobic block and amphiphilic block with hydrophobic groups in the backbone and pendant polar groups. The equilibrium parameters of the polymer globules of different shapes are determined using the mean-field approach to determine the most favorable structure. Morphological diagrams of condensed macromolecules are presented depending on the chain length, amphiphilic block fraction, interaction parameters, and pendant volume and length. The diagrams are compared with those of a copolymer molecule with the same fraction of amphiphilic monomer units which are regularly distributed along the chain. The diblock copolymer molecule is found to form a single spherical or flattened particle, with the core from the hydrophobic block, or a granular micelle consisting of spherical or nearly spherical particles, in agreement with the experimental data in the literature. The optimal chain parameters for self-assembly into a stable single core-shell particle are predicted.


Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4408
Author(s):  
Chang-Cheng Wang ◽  
Rong Zhang ◽  
Shiqi Li ◽  
Guangsu Huang ◽  
Maozhu Tang ◽  
...  

The tuning of binding modes of polar groups is the key step to mimicking the structure and properties of natural rubber through the molecular design of synthetic polyisoprenes. Herein, the ordering and binding distances of oligopeptides could be altered systematically by changing their lengths and distribution along the polyisoprene chain, which impose huge impacts on the mechanical properties and chain dynamics of green rubber. In detail, a series of peptide-functionalized polyisoprenes with terminal blocks (B-2A-PIP, B-3A-PIP) or random sequences (R-2A-PIP, R-3A-PIP) are fabricated by using dipeptides (2A) or tripeptides (3A) as crosslinkers to explore the mechanism of terminal interaction on mechanism properties and chain dynamics. B-4A-PIP and R-4A-PIP served as control samples. It is found that the increased oligopeptide length and the block distribution improves the mechanical properties and confine the chain movement by elevate the contents of ordered and compact microstructures, which is indicated by XRD, broadband dielectric spectroscopy (BDS) and consistent with the result of molecular dynamics simulation. New relaxation signals belonging to oligopeptide aggregates are found which showed elevated dielectric strengths upon temperatures increase. Additionally, it also reveals that the binding modes of oligopeptide do not significantly influence the entanglements of polyisoprene.


Molbank ◽  
10.3390/m1303 ◽  
2021 ◽  
Vol 2021 (4) ◽  
pp. M1303
Author(s):  
Ramiz Hoti ◽  
Hamit Ismaili ◽  
Veprim Thaçi ◽  
Gjyle Mulliqi-Osmani ◽  
Malësore Pllana-Zeqiri ◽  
...  

Synthesis of a series of the substituted [(pyridinyl and pyrimidin-2-ylimino)-ethyl]-4-hydroxy-chromen-2-ones and their tetrazole derivates is presented in this study. By catalytic condensation of 4-hydroxy-3-acetylcoumarine 2 and 2-aminopyridines 3(a-d), 3-[(pyridin-2-ylimino)-ethyl]-4-hydroxy-chromen-2-ones 4(a-d) are synthesized in high yield. During the condensation reaction of 2 and 4-amino-2,6-dihydroxypyrimidine 3e, 3-[1-(2,6-Dihydroxy-pyrimidin-4-ylimino)-ethyl]-4-hydroxy-chromen-2-one 4e as condensation products is synthesized. In following series, by cyclization reactions of compounds 4 (a-e) with sodium azide, analogue 3-substituted pyridin-2-yl and pyrimidin-2-yl-5-methyl-2,5-dihydro-1H-tetrazol-5-yl]-4-hydroxy-chromen-2-one 5(a-e) are synthesized the products. Structural characterization of the synthesized products is done on the basis of spectrometric data. Antibacterial activity of the compounds 4(a-e) and 5(a-e) against S. aureus, E. coli and Klebsiella was examined by measuring the inhibition zones around the disks marked with the corresponding products solution. The impact of substitutions in antimicrobial is also explored. Compounds with polar groups have shown significant antibacterial activity against these microorganisms.


Polymer ◽  
2021 ◽  
pp. 124467
Author(s):  
Noorullah Baig ◽  
Suchetha Shetty ◽  
Sheik Saleem Pasha ◽  
Sumit Kumar Pramanik ◽  
Bassam Alameddine

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1422
Author(s):  
Ciara Byrne ◽  
Alenka Ristić ◽  
Suzana Mal ◽  
Mojca Opresnik ◽  
Nataša Zabukovec Logar

The increasing demand for heating/cooling is of grave concern due to the ever-increasing population. One method that addresses this issue and uses renewable energy is Thermochemical Energy Storage (TCES), which is based on the reversible chemical reactions and/or sorption processes of gases in solids or liquids. Zeolitic imidazolate frameworks (ZIFs), composed of transition metal ions (Zn, Co, etc.) and imidazolate linkers, have gained significant interest recently as porous adsorbents in low temperature sorption-based TES (sun/waste heat). In this study, we examined two different sodalite-type ZIF structures (ZIF-8 and ZIF-90) for their potential heat storage applications, based on the adsorption of water, methanol and ethanol as adsorbates. Both ZIF structures were analysed using PXRD, TGA, SEM and N2 physisorption while the % adsorbate uptake and desorption enthalpy was evaluated using TGA and DSC analysis, respectively. Among the studied adsorbent–adsorbate pairs, ZIF-90-water showed the highest desorption enthalpy, the fastest sorption kinetics and, therefore, the best potential for use in heat storage/reallocation applications. This was due to its significantly smaller particle size and higher specific surface area, and the presence of mesoporosity as well as polar groups in ZIF-90 when compared to ZIF-8.


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