Calculation and Analysis of the Molecular Weight Characteristics of the Polymer in the Synthesis of Butyl Rubber

The article compiled a mathematical model of the cationic copolymerization of isobutylene and isoprene using a catalyst AlCl3 in a CH3Cl solution, including the reactions of initiation, chain growth, chain transfer to the monomer, and chain termination. The molecular weight characteristics of butyl rubber synthesized in methyl chloride using a catalytic system based on aluminum trichloride have been investigated. Relationships are obtained for calculating the moments of the molecular weight characteristics of butyl rubber. The effect of the concentration of the initiator on the conversion versus time was investigated.

A Versatile Equilibrium Method for the Synthesis of High-Strength, Ladder-like Polyphenylsilsesquioxanes with Finely Tunable Molecular Parameters

A versatile equilibrium method for synthesizing ladder-like polyphenylsilsesquioxanes (L-PPSQs) with various molecular weights (from 4 to 500 kDa) in liquid ammonia was developed. The effect of diverse parameters, such as temperature, monomer concentration, reaction time, addition or removal of water from the reaction medium, on the polycondensation process was determined. The molecular weight characteristics and structure of the L-PPSQ elements obtained were determined by GPC, 1H, 29Si NMR, IR spectroscopy, viscometry, and PXRD methods. The physicochemical properties of L-PPSQs were determined by TGA and mechanical analyses.

Molecular Brushes with a Polyimide Backbone and Poly(ε-Caprolactone) Side Chains by the Combination of ATRP, ROP, and CuAAC

An approach to the synthesis of the novel molecular brushes with a polyimide (PI) backbone and poly(ε-caprolactone) (PCL) side chains was developed. To obtain such copolymers, a combination of various synthesis methods was used, including polycondensation, atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), and Cu (I)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC). ATRP of 2-hydroxyethyl methacrylate (HEMA) on PI macroinitiator followed by ROP of ε-caprolactone (CL) provided a “brush on brush” structure PI-g-(PHEMA-g-PCL). For the synthesis of PI-g-PCL two synthetic routes combining ROP and CuAAC were compared: (1) polymer-analogous transformations of a multicenter PI macroinitiator with an initiating hydroxyl group separated from the main chain by a triazole ring followed by ROP of CL, or (2) a separate synthesis of macromonomers with the desirable functional groups (polyimide with azide groups and PCL with terminal alkyne groups), followed by a click reaction. Results showed that the first approach allows to obtain graft copolymers with a PI backbone and relatively short PCL side chains. While the implementation of the second approach leads to a more significant increase in the molecular weight, but unreacted linear PCL remains in the system. Obtained macroinitiators and copolymers were characterized using 1H NMR and IR spectroscopy, their molecular weight characteristics were determined by SEC with triple detection. TGA and DSC were used to determine their thermal properties. X-ray scattering data showed that the introduction of a polyimide block into the polycaprolactone matrix did not change the degree of crystallinity of PCL.

ISOLATION AND STUDY OF THE POLYSACCHARIDE COMPLEX ISOLATED FROM AESCULUS HIPPOCASTA-NUM L.

This paper presents the results of a study of the polysaccharide complex, first obtained using microwave radiation from the shells of horse chestnut seeds (Aesculus Hippocastanum L.), collected on the territory of the Tashkent region of the Republic of Uzbekistan. It is shown that the use of microwave waves makes it possible to intensify the method of obtaining polysaccharides with an increase in their yield. The yield of the obtained product reaches 13%, compared with the method of obtaining without using microwave radiation (9.85%), which indicates the prospects of using microwave radiation in the isolation of polysaccharides from this type of raw material. The molecular weight characteristics were determined, and using GC/MS analysis of trimethylsilyl derivatives, the monosaccharide composition of the complex isolated from the shells of the Semyon chestnut by alkaline extraction was established. It was found that the isolated polysaccharides consist mainly of arabinose and galactose residues (65–100%), and also, as minor monosaccharides, up to 35% of glucose, xylose, mannose, rhamnose, ribose residues. Signals and absorption bands corresponding to total polysaccharides were observed in 13C NMR and IR spectra. The NMR analysis data are consistent with the results of the analysis of the monosaccharide composition of the polysaccharide complex obtained using GC / MS. The antiradical activity of the polysaccharide complex has been established.

Synthesis of Complex Oligoesters Based on Adipic Acid, Ethanediol and Butanediol-1,4 with Specified Characteristics

Aliphatic linear oligoesters with terminal hydroxyl groups and given molecular weight characteristics, hydroxyl and acid numbers were synthesized by esterification of adipic acid, ethylene glycol and butanediol-1,4. It was found that the main properties of complex oligoesters largely depend on the ratio of the starting reagents. The kinetic regularities of the process of esterification of adipic acid, ethylene glycol and butanediol-1,4 have been studied and determined. It was found that the duration of the vacuum stage of esterification in the presence of organomodified montmorillonite is noticeably shorter than when using a commercial catalyst.

Gel-permeation chromatography as a method for monitoring transformations of heavy petroleum fractions during secondary oil refining

A rapid and easy to use method for monitoring transformations of heavy oil fractions during secondary processes of oil refining is proposed. The method is based on the study of changes in the molecular weight characteristics by gel-permeation chromatography (GPC) using a refractometric detector. Optimal conditions for registration of the chromatograms (temperature, eluent consumption and its composition) were specified. Heptane, toluene, and toluene added with 1% and 5% of methanol were studied as eluents, the polarity indices being arranged in a series 0.2; 2.4; 2.43; 2.54. The effect of the nature of the solvent on the type of the product chromatogram is determined. It is shown that addition of a polar solvent to a nonpolar one increases the polarity index, reduces both the degree of association of petroleum molecules and adsorption on the gel. The most available toluene which meets the GPC requirements is chosen as an eluent. Addition of 1% CH3OH to the eluent promotes suppression of polyelectrolyte effects and adsorption. The revealed absence of the dependence of the retained volume and the type of chromatograms on the eluent flow rate and temperature indicates that separation is carried out under conditions of exclusion and completely obeys the theory of exclusive liquid chromatography. The transformation of raw materials during a technological process of oil production at the JSC «ANKhK» was studied using the GPC method under above-mentioned chromatographic conditions. We have studied vacuum distillate of the primary oil refining unit ELOU+AVT-6 (VD) and the product of hydrocracking of the vacuum distillate of the 123PM unit (HVD). It is shown that determination of the molecular weight characteristics provides an important information about the behavior of technological processes. The HVD meets the requirements for hydrocracking products. A decrease in the content of aromatic hydrocarbons in comparison with the raw feedstock is proved by the data of thin layer chromatography (TLC).

Development of a Promising Method for Producing Oligomeric Mixture of Branched Alkylene Guanidines to Improve Substance Quality and Evaluate Their Antiviral Activity against SARS-CoV-2

This paper reports the synthesis of branched alkylene guanidines using microfluidic technologies. We describe the preparation of guanidine derivatives at lower temperatures, and with significantly less time than that required in the previously applicable method. Furthermore, the use of microfluidics allows the attainment of high-purity products with a low residual monomer content, which can expand the range of applications of this class of compounds. For all the samples obtained, the molecular-weight characteristics are calculated, based on which the optimal condensation conditions are established. Additionally, in this work, the antiviral activity of the alkylene guanidine salt against the SARS-CoV-2 virus is confirmed.

Differences in the standardization of medicinal products based on extracts of chondroitin sulfate

Objective: a comparative analysis of 6 different chondroprotectors for injection, containing chondroitin sulfate (CS) based on natural extracts.Material and methods. Five samples were studied for each CS extract. The preparations were compared on the basis of profiles of trace element composition, sulfur content, chromatographic analysis and test for total protein. In each sample, the concentration of 72 elements was determined, then averaging was performed and the variances of the content of each element were calculated. To assess the content of the protein fraction, a modified Lowry method with bicincholic acid was used. Chromatographic profiles of the studied CS extracts were measured to estimate the molecular weight distribution.Results. The studied samples differ significantly from each other in the total and individual content of sulfur, toxic and conditionally toxic microelements. According to the analysis of sulfur and trace elements, a cluster of more standardized CS extracts was identified. It was shown that the assessments of the pharmaceutical quality of the studied extracts made by the elemental profile, correspond to the assessments of the quality by the degree of proteins elimination and by the molecular weight characteristics of CS extracts. In particular, the highest total content of toxic elements was found for CS-6 (14.87±1.81 μg/l) and CS-2 (9.20±1.12 μg/l), and the lowest – for CS-4 (1.46±0.23 μg/l), CS-3 (1.92±0.33 μg/l) and CS-1 (2.98±0.25 μg/l). The highest content of protein impurities was also found in CS-6 (9.62 mg/ml) and CS-2 (6.64 mg/ml), and the lowest – in CS-1 (2.87 mg/ml). At the same time, the highest amount of sulfur was found CS-1 (6400 mg/kg) and much less – for CS-2 (370 mg/kg) and CS-6 (100 mg/kg). Significant amounts of the high-molecular fraction of CS (1–40 kDa) were found only in CS-1, and only trace amounts of high-molecular CS forms were present in CS-2 and CS-6.Conclusion. The highest content of cholesterol and sulfur and, at the same time, the lowest content of toxic microelements and proteins were distinguished by the extract obtained from the trachea of a bovine.