Molecular-mass Characteristics Research Articles

Isoprene Polymerization in the Presence of Phosphate Catalytic Systems Based on a Mixture of Neodymium and Gadolinium Salts

Coordination polymerization of isoprene in the presence of Ziegler–Natta catalytic systems based on a mixture of neodymium and gadolinium bis(2-ethylhexyl) phosphates at the neodymium/gadolinium molar ratios of 25/75, 50/50, and 75/25 was studied. These catalytic systems exhibit high catalytic activity in isoprene polymerization, equal to that of the catalytic system based on neodymium bis(2-ethylhexyl) phosphate. The influence of the Nd/Gd ratio on the molecular-mass characteristics and microstructure of the polymers obtained was examined. The kinetic parameters of the isoprene polymerization using catalytic systems based on a mixture of neodymium and gadolinium salts were determined. The possibility of using such systems in the synthesis of stereoregular cis-1,4-polyisoprene with the optimum level of molecular masses was demonstrated

New Ways of Controlling the Molecular Mass Characteristics and Distribution of Branches for Polyethylene Synthesized over Supported Catalysts Containing Fe(II) Bis(imino)pyridyl and Ni(II) Bis(imine) Complexes

New Ways of Controlling the Molecular Mass Characteristics and Distribution of Branches for Polyethylene Synthesized over Supported Catalysts Containing Fe(II) Bis(imino)pyridyl and Ni(II) Bis(imine) Complexes

Molecular mass characteristics of poly(methyl methacrylate) obtained by solution polymerization in the presence of ferrocene

The study of the effect of ferrocene on the molecular weight and polydispersity of poly(methyl methacrylate) obtained by polymerization in solvents differing in polarity (benzene, toluene, ethyl acetate) was carried out. It is shown that both the mass and the number average molecular weights of poly(methyl methacrylate) decrease, and the polydispersity is preserved. It has been found that during the process in the most polar ethyl acetate, the effect of ferrocene on the molecular weight is most significant. Keywords: methyl methacrylate; ferrocene; solution polymerization; solvent polarity.

Free-radical polymerization in a droplet with initiation at the interface

The free-radical polymerization inside monomer droplets surrounded by an immiscible liquid of the initiator solution is studied before the gel effect by means of the generalized method of moments taking into account diffusion of radicals and polymer chains. The influence of the droplet radius and initiator concentration in the surrounding phase on the polymerization kinetics and molecular mass characteristics of the synthesized polymer is analyzed. It is found that the polymerization kinetics matches the bulk polymerization when the droplet is small enough (kinetic regime). However, increasing the droplet radius leads to a diffusion-kinetic regime, in which the polymerization rate becomes significantly lower. As a result, the average length and the dispersity of the produced polymer chains depend significantly on the monomer droplet size. The dependence of the effective polymerization rate coefficient on the droplet radius and the initiator concentration is discussed.

Biocide Coating from Polydiallyldimethylammonium Chloride—What Molecular Weight Should We Choose?

Biocidal compositions based on interpolyelectrolyte complexes and a low molecular weight antibiotic can become a promising material for creating biocidal coatings, as they combine wash-off resistance and dual biocidal action due to the biocide and the polycation. Molecular mass characteristics of polymers play an essential role in the physics and mechanical properties of the coatings. In this work, the properties of polydiallyldimethylammonium chloride (PDADMAC) coatings of various molecular weights are investigated and assumptions are made about the optimal molecular weight needed to create antibacterial compositions. To study the resistance to washing off and moisture saturation of the coatings, the gravimetric method was used, and the adhesive properties of the coatings were studied by dynamometry. It has been established that an increase in molecular weight affects the wash-off resistance of coatings, but does not affect moisture absorption and adhesion mechanics of coatings. All samples of PDADMAC were demonstrated to exhibit the same antibacterial activity. Thus, when developing systems for creating antibacterial coatings, it must be taken into account that in order to create stable coatings, the requirement to use PDADMAC with a high degree of polymerization is necessary for the coating desorption control during wash off-but not mandatory for the control of mechanical and antibacterial properties of the coating.

Synthesis of Ph<sub>3</sub>Sb(O<sub>2</sub>CR)<sub>2</sub> Compounds with Unsaturated Carboxylic Acids and Use of Triphenylantimony Dicrotonate for the Production of Sb-Containing Polymers

The reaction of triphenylantimony with ROOH peroxides (R = t -Bu, H) and unsaturated carboxylic acids afforded triphenylantimony dicarboxylates Ph3Sb(O2CCH=CH2)2, Ph3Sb(O2CCMe=CH2)2, Ph3Sb(O2CCH=CHMe)2, Ph3Sb(O2CCH=CHPh)2, Ph3Sb(O2CCH=CHC6H4NO2-3)2, Ph3Sb(O2CCH=CHC4H3O)2, Ph3Sb(O2CCH=CH-C6H4OMe-4)2, Ph3Sb(O2CCH=CHCH=CHMe)2, Ph3Sb(O2CCH2CH=CH2)2, p -Tol3Sb(O2CCH=CHPh)2 with yields of 35-86%. The comparison of the obtained compounds structure using the structural parameter τ (from the X-ray diffraction data), as well as the difference in the values of νas(COO) and νs(COO) (from the IR data) was investigated. In all compounds, the coordination of the antimony atom occupies an intermediate position between the trigonal-bipyramidal and tetragonal-pyramidal. In all compounds, there is an additional coordination of the antimony atom on carbonyl oxygen atoms. Intermolecular interactions in acrylate, methacrylate, crotonate and triphenylantimony sorbate with the participation of C=C double bonds of unsaturated carboxylate fragments of neighboring molecules located on top of each other were revealed. Antimony-containing transparent polymers - polymethyl methacrylate and polystyrene, which may be of practical value for the creation of new composite materials, have been synthesized on the basis of triphenylantimony dicrotonate. The molecular mass characteristics of polymers, the absorption of X-rays, UV light by the obtained polymers were measured.

Polyelektrolite Solutions and Molecular Descriptions of Biopolymer Macroions

Molecular mass characteristics of samples of ionic biopolymers, including chitosan and fibroin, the manifestation of physical conditions depending on the concentration of macroions, and hydrodynamic, rheological methods were used in the implementation of these studies. These processes depend on the fact that ionic polymers exhibit viscosity in relation to their molecular mass and are sensitive to the effects of the electric field at the expense of ionogenic groups. In order to determine this, the results of studies on the molecular characteristics of basic polymer objects were discussed. When polyelectrolytes are affected by external forces, including mechanical or electrical stresses, gradient fields are created, and macroions move along the lines of force of these fields. Such fields are observed, for example, when a liquid flows from a capillary under mechanical pressure, when the liquid is turned into a stable laminar flow using a rotor, or when ions and macroions move towards the poles (electrodes) during electrophoresis and electrolysis. In general, in the gradient field created under the influence of mechanical influence, the macroions move along the lines of force in rotation and advance, while in the gradient field created under the influence of electric voltage, the functional groups of macroions move towards the anode or cathode as anions or cations. The reason for the choice of poles is the sensitivity of anions or cations to the effect of an electric field.

OLIGOMERIC GUANIDINE-CONTAINING PROTON CATIONIC IONIC LIQUID

Oligomeric ionic liquids occupy an intermediate position between low molecular weight and polymeric. They are promising as polymer electrolytes in electrochemical devices for various purposes, membranes for the separation of gas mixtures, in sensor technologies, and so on. Oligomeric guanidinium ionic liquids are practically not described in the literature. In terms of studying the effect of the structure of the epoxy component on the properties of oligomeric ionic liquids of this type, it is advisable to introduce into its composition an aliphatic oligoether component. The choice of aliphatic oligoepoxide for the synthesis of guanidinium oligomeric ionic liquids is based on the fact that it is structurally similar to poly - and oligoethylene oxides, which are known to be non-toxic, biodegradable, and reactive oligomeric ionic liquids at elevated temperatures. A new type of reactive oligomeric proton cationic ionic liquid was synthesized by the reaction of oligomeric aliphatic diepoxide with guanidine, followed by neutralization of the product with hydrochloric acid. In this study, the synthesis of proton cationic oligomeric ionic liquids was based on the introduction of guanidinium fragments as end groups of the oligoether aliphatic chain. This reaction is attractive because of the ease of opening the oxirane ring with such a strong nucleophile as guanidine.The reaction forms a fragment with an aliphatic C-N bond, which retains the high basicity of the nitrogen atom. Its structure is characterized by the presence of guanidinium groups at the ends of the aliphatic hydroxyl-containing oligoether chain. The chemical structure of this compound is characterized by IR -, 1H ,13 C NMR spectroscopy methods, and its molecular mass characteristics are determined.The average molecular weight of the synthesized oligomeric ionic liquids is 610 g / mol.The value of the coefficient of polydispersity of the synthesized oligomeric ionic liquids is equal to 1.2. Determination of the content of amino groups in the guanidine-containing oligomer in the basic form by titrometric method allowed to establish that the value found is close to the theoretically calculated value. The synthesized oligomeric proton ionic liquid is characterized by an amorphous structure with two glass transition temperatures. The first lies in the range -70 °C, the second in the region of 70 °C, and the beginning of thermal oxidative destruction is located in the region of 148 °C. The temperature dependence of the ionic conductivity for this compound is nonlinear in the Arrhenius coordinates, which indicates the realization of ionic conductivity mainly due to the free volume in the system. The proton conductivity of this compound is 6.4·10-5–1·10-2Cm/cmin the range of 20–100 °C. The obtained compound exhibits surface-active properties characteristic of classical surfactants, as evidenced by the value of the limiting surface activity – 2.8·102 Nm2 / kmol. The value of CCM is 1.8·10-2 mol/l., and the value of the minimum surface tension – 37.70 mN / m. The synthesized oligomeric ionic liquid is of interest as electrolytes operating under anhydrous conditions, surfactants, disinfectants, and starting reagents for the synthesis of ion-containing blockopolymers.

Nanodispersions of Polyelectrolytes Based on Humic Substances: Isolation, Physico-Chemical Characterization and Evaluation of Biological Activity.

Natural polyelectrolytes, including in the form of complexes with colloidal particles, are increasingly used in pharmacy due to the possibility of regulated attachment of medicinal substances and their targeted delivery to the target organ. However, the formation, stability, and molecular-mass characteristics of polyelectrolyte nanodispersions (ND) vary depending on the nature and composition of the medium of their origin. This is due to the lack of standardized approaches to quality control and regulatory documentation for most natural ND. In this paper, we first introduced the isolation, followed by investigations into their physico-chemical properties and bioactivity. Using the dried droplet method, we were able to detect the “coffee ring effect”. Fractographic studies of the surface structure of EHA and FA dried samples using SEM showed its heterogeneity and the presence of submicron particles encapsulated in the internal molecular cavities of polyelectrolyte. FTIR spectroscopy revealed the ND chemical structure of benzo-α-pyron and benzo-γ-pyron, consisting of nanoparticles and a branched frame part. The main elements detected by X-ray fluorescence in humic substance extract and fulvic acid include Si, P, S, K, Ca, Mn, Fe, Cu, Zn, whereas Fe is in high concentrations. The UV-spectra and fluorescent radiation demonstrated the possibility of studying the effect of the fulvate chromone structure on its optical properties. It is shown that dilution of the initial solutions of polyelectrolytes 1:10 contributes to the detection of smaller nanoparticles and an increase in the absolute value of the negative ζ-potential as a factor of ND stability. A study of the EHS effect on the SARS-CoV-2 virus infectious titer in the Vero E6 cell showed the effective against virus both in the virucidal scheme (the SI is 11.90–22.43) and treatment/prevention scheme (the SI is 34.85–57.33). We assume that polyelectrolyte ND prevent the binding of the coronavirus spike glycoprotein to the receptor. Taking into account the results obtained, we expect that the developed approach can become unified for the standardization of the ND natural polyelectrolytes complex, which has great prospects for use in pharmacy and medicine as a drug with antiviral activity.

Relationship of Molecular-Mass Characteristics of Polyisoprene, Component of Vulcanized Sealant, with Particle Sizes of Catalytic System TiCl4–Al(i-C4H9)3 in Isoprene Polymerization

Relationship of Molecular-Mass Characteristics of Polyisoprene, Component of Vulcanized Sealant, with Particle Sizes of Catalytic System TiCl4–Al(i-C4H9)3 in Isoprene Polymerization

Non-accumulative in the environment facile hydrophobic coatings based on branched siloxanes with perfluoroalkyl substituents

Based on triethoxy(3-(1,1,1,2,5,5,5-hepatfluoro3 - (perfluoropropan-2-yl) - 4-(trifluoromethyl)pent-3-en-2-yl) oxy)propylsilane, obtained from the commercially available trimer hexafluoropropylene, branched oligosiloxanes were synthesized by hydrolytic polycondensation in the active medium . The resulting polymers were studied by NMR and IR spectroscopy, and their molecular mass characteristics were investigated by GPC. In order to create stable hydrophobic coatings, the dependence of the hydrophobic properties of the resulting coatings on the surface of glass and aluminum on the conditions of polymer synthesis was studied. It has been shown that changes in the nature of the active medium (acetic or trifluoroacetic acid), the synthesis temperature, and the ratio of monomers:the active medium results in a polymer with similar molecular weights. For polymer coatings with the highest molecular weight Mw = 21.6 × 103, the average values of contact angles on glass and aluminum were 113 and 114°, respectively. In addition, condensation of the triethoxyl derivative of the hexafluoropropylene trimer with phenyltrimethoxysilane produced a modifier for hydrophobizing the surface of epoxy resins. When mixed into an epoxy resin up to 1.5% by weight of the resulting copolymer, resins with a contact angle of up to 113° were obtained.

Densely Cross-Linked Polysiloxane Nanogels

Nanogels can be called the new old§ objects of polymer chemistry. New because we have formulated the criteria for the assignment of objects to this group within the macromolecule-particle concept and developed the methods for their directed and controlled synthesis. Old because the application of these criteria to the earlier known systems allow us to surely classify them as nanogels. It is shown that this classification per se provides insight into the organization of their molecular structures and enables directed modification. This means a transition from the empirical control of the properties to molecular design. The current review presents a brief historical overview of densely cross-linked nanogels and their main synthetic routes and highlights the principles and approaches to the control of their structures and molecular-mass characteristics, application scope, and prospects for further development.

Эффективность протеаз панкреатина и трипсина при ферментативном гидролизе коллагена

The analysis of molecular-mass characteristics (MMC) / molecular mass (MM) and polydispersity coefficient (PC) of high molecular weight fish collagen (FC) hydrolysate has been carried out in the process of enzymatic hydrolysis by two proteolytic enzymes: pancreatin and trypsin at room temperature. High efficiency of enzymes has been shown: the main part of FC is hydrolyzed within the first minute in the case of both pancreatin and trypsin. As a result, several fractions of FC hydrolysate are formed. A small oligomeric fraction is observed in the case of trypsin. The values of the polydispersity coefficient M w / M n for fractions in the hydrolysis process are typically no more than 1.2. This indicates the homogeneity of collagen fractions in MM. The original native FC with MM ~ 300 kDa is absent in the hydrolysate fractions. These data indicate a high hydrolysis rate in the presence of these enzymes. Formation of two low-molecular fractions of hydrolysate with close values of MM ~ 17 kDa and ~ 9 kDa has been observed for both enzymes, and the share of the latter fraction in the solution is more than 80 %. Further control of MMC has shown that there is a slow decrease in the proportion of all fractions, to almost complete disappearance in three days, except for the low-molecular fraction with MM ~ 9 kDa, the content of which gradually increases. The type of molecular weight distribution curves for different enzymes is almost the same. However, there is a small difference in the ratio of hydrolysate fractions at different stages of hydrolysis with the use of these enzymes, due to a minor difference in the efficiency of the enzymes used, which may affect the structure of the scaffold during its formation. Differences in the MM values and the ratio of fractions with different MM indicate the influence of the enzyme nature on hydrolysis of high-molecular collagen. The presented results are in good agreement with the known literature data on the nature of pancreatin enzymes (it contains the proteolytic enzymes: trypsin, pepsin and chymotrypsin). These three proteases catalyze the hydrolysis of peptide bonds formed by residues of the amino acids arginine and lysine. The strongly pronounced limited substrate specificity of enzymes leads to practically quantitative formation of a narrowly dispersed oligomer with MM ~ 9 kDa in the process of hydrolysis. In combination with the results of research on the effect of enzymes upon other components of the scaffold design, as well as biomimetic tests, these will model the composition, structure, and major characteristics of scaffolds with the optimized properties. This is especially important if the enzymatic hydrolysis reactions are used in formation of scaffolds and biomedical cell products, because the resulting cell matrix is formed not from the native molecules, but from their hydrolysates.

Thiol-ene coupling reaction achievement and monitoring by "in situ" UV irradiation NMR spectroscopy.

In this study, the possibilities of a new “in situ” LED UV illumination NMR spectroscopic technique for performing an initiator-free thiol–ene “click” coupling reaction of an allyl-functionalized poly(allyl glycidyl ether) (PAGE) prepolymer with a number of mono- and di-oligo polyethylene glycol (PEG) thiols is demonstrated. The state-of-the-art setup constructed with LEDs as UV light sources that illuminate through optical fibers directly into an NMR testing tube at a fixed wavelength of 365 nm is appropriate for various polymeric materials and biologically active substances. The selected experimental protocol uses a series of periods of irradiation and dark periods, thus providing opportunities to conduct an effective thiol–ene “click” reaction and simultaneously study the kinetics of the photochemical reaction with the exposure time, as well as macromolecular association directly in a solution applying the whole types of NMR methods: from conventional 1H or 13C NMR to diffusion NMR spectroscopy (DOSY). In addition, the molecular mass characteristics of the prepared copolymers were studied by gel-permeation chromatography (GPC). The observed differences in the reaction rates as well as in the size of species formed (the corresponding hydrodynamic radiuses Rh of aggregates) as a result of the coupling process of parent PAGE prepolymers and model PEG thiols were thoroughly discussed and the reaction pathway proposed.

Creating molecular weight distribution of butadiene rubber on neodymium-based catalytic system

The method of calculation of the molecular weight distribution (MWD) of rubber SDRN synthesized in the cascade of reactors with a continuous mixer in the presence of chain transfer to the polymer (by direct numerical solution system of equations arising from the kinetic scheme of polymerization with special selection of boundary conditions, maximum length of macromolecules and calculation step value). Numerical solution of mathematical model that is systems of differential equations for concentrations of monomer, co-catalyst and macromolecules of polymer together with thermal balance is obtained. The influence of regime parameters on MWD and molecular mass characteristics of the final product obtained using molecular weight distribution are analyzed.

Ultrafiltration Membranes Based on Various Acrylonitrile Copolymers

The structure and properties of ultrafiltration membranes synthesized from bicomponent solutions in N,N-dimethylformamide using five commercial acrylonitrile copolymers of various compositions and molecular masses have been studied. The molecular mass characteristics of the copolymers (Mw, Mw/Mn) have been determined; the viscosity properties of dilute and concentrated solutions have been studied. It has been shown that depending on the chemical composition and molecular mass of the copolymer, the concentration dependence of the water flux is different: for copolymers with a molecular mass of Mw of 76 000–81 000 g/mol, with an increase in the copolymer concentration in solution from 12 to 16%, the water flux of the membranes decreases from 300–500 to 40–150 L/(m2 h) depending on the copolymer composition. For samples with a higher molecular mass (Mw = 99 000 and 107 000 g/mol), the water flux of the membranes hardly depends on the copolymer concentration in the casting solution; it is 150 and 75 L/(m2 h), respectively. The rejection factor of the membranes with a molecular mass of 40 000 g/mol for polyvinylpyrrolidone increases with increasing copolymer concentration in the casting solution regardless of the chemical composition and molecular mass of the copolymer. Scanning electron microscopy studies of the membrane structure have shown that membranes synthesized from copolymers with a higher molecular mass have a denser structure and a thicker selective layer than the respective parameters of membranes synthesized from acrylonitrile copolymers with a lower molecular mass, which are characterized by the presence of large macrovoids in the membrane matrix. These differences in the membrane structure are attributed to different viscosities of the casting solutions at identical copolymer concentrations.

Radical-Initiated (Co)polymerization of Methacrylates in the Presence of Organometallic Iron Complexes

The effect exerted by organometallic iron complexes (ferrocene, tricarbonyl cyclooctatetraene iron, and dimer cyclopentadienyldicarbonyl iron) on the benzoyl peroxide initiated homo- and copolymerization of methyl methacrylate and n-butyl methacrylate was studied. The ligand surrounding in the organometallic complexes influences the shape of the kinetic curves of the methyl methacrylate and n-butyl methacrylate polymerization. In the presence of organometallic iron complexes, the copolymerization constants are close to unity. That is, the azeotropic copolymerization occurs, with the copolymer composition equal to the composition of the monomer mixture and with the random distribution of monomeric units in the copolymer chain. On the other hand, the presence of metallocenes influences the microstructure and molecular-mass characteristics of the copolymers. These changes are due to the formation of macromolecules with the participation of both free radicals and coordination-active polymerization sites formed in the presence of organometallic complexes.

Numerical study of polymerization processes on various catalytic systems

A set of algorithms for determining the averaged molecular characteristics of the polymer and finding the optimal initial concentrations was built on the basis of the mathematical software for solving rigid and non-rigid systems of ordinary differential equations describing various polymerization processes. With the help of the developed mathematical and software computational experiments were carried out for various technological parameters and production recipes for the considered processes. The dependencies of the molecular mass characteristics of the copolymer on the time of polymerization or conversion of monomers were built, which showed agreement with the data obtained as a result of experiments in the central factory laboratory of Synthez-Kauchuk OJSC (Sterlitamak, Republic of Bashkortostan) and the laboratory of physico-chemical studies of polymers of BashSU.

Synthesis and Physico-chemical Properties of (Co)polymers of 2-[(2E)-1-methyl-2-buten-1-yl]aniline and Aniline

A new soluble polymer on 2-[(2E)-1-methyl-2-buten-1-yl]aniline and its copolymers with aniline basis have been synthesized in various molar ratios. For all samples, the electrical conductivity, morphology, solubility, electrochemical properties, as well as spectral and molecular mass characteristics have been studied, and a comparative analysis with polyaniline has been carried out. The substituent introduced into the aniline aromatic ring significantly improves the solubility in typical organic solvents of a high molecular weight product. The morphology of the test compounds depends on the co-monomer ratio. As the content of the substituted aniline in the initial mixture increases, the morphology of the polymer changes from the inherent polyaniline fibrous microstructure to the globular one with irregular substituted polyaniline shapes and sizes. Electrochemical study of the samples revealed that the higher the oxidation potential, the wider the band gap (ranging from 2.00 to 2.15). The electrical conductivity decreases in proportion to the increase in the substituted aniline concentration of the initial co-monomer mixture and amounts to 12.5–35.7 × 106 nSm.

Effect of Physical Factors during the Preparation of a Reaction Mixture in Turbulent Flows on the Rate of Butadiene Polymerization in the Presence of TiCl4-Al(i-C4H9)3 and Molecular Mass Characteristics of Butadiene Rubber

Butadiene polymerization was used as a model of diene polymerization in the presence of micro-heterogeneous Ziegler-Natta polycentric catalytic systems (TiCl4-Al(i-C4H9)3 catalytic system, toluene solvent, temperature 298 K). It was found that an increase in the rate of feeding of the reaction mixture into a tubular turbulent apparatus of diffuser-confuser design, the ratio of diffuser to confuser diameters, and diffuser opening angle led to a local increase in the kinetic energy and dissipation rate of turbulence; as a consequence, the most probable equivalent radius of the catalyst particles and the average molecular mass of the polymer decreased, while the polymerization rate increased. It was also found that a change in the section length to diffuser diameter ratio when the former or latter was constant and a change in the number of sections of the tubular turbulent apparatus from four to eight did not affect the polymerization rate and the molecular mass characteristics of the polymer.