Copolymer Macromolecules Research Articles

Chemical transformations during mechanoactivation of ε‐polylysine‐poly‐L‐lactic acid mixture to obtain amphiphilic copolymers

AbstractIn this study presents a new strategy for the preparation of amphiphilic copolymers of ε‐polylysine (PL) and poly‐L‐lactic acid (PLA) using one‐step pulsed mechanochemical approach. Correlation between the synthesis parameters (ratio of homopolymers) and the structure of the resulting copolymers has been studied. The interaction products were characterized by nuclear magnetic resonance, Infrared spectroscopy, size‐exclusion chromatography, by varying the mass ratio of the initial homopolymers (PL:PLA = 10:90; 50:50; 90:10). It is shown that the largest number of product yield is formed in a ratio of homopolymers of 50:50, according to the reaction of aminolysis of polyesters. The dynamic light scattering method, transmission electron microscopy, and small‐angle x‐ray scattering were used to characterize nanoscale structures of copolymer macromolecules in aqueous solvent. As a result of pulsed mechanochemical action at all three ratios of homopolymers (PL:PLA = 10:90; 50:50; 90:10 w/w), the aminolysis reaction of the ester group occurs and branched macromolecules of copolymers are formed, which consist of chemically related sequences of homopolymers—main chain—PL, side branches—PLA. However, the maximum yield of the amphiphilic copolymer was 90 wt% with a PL:PLA ratio of 50:50. This study can serve as the development of important areas: deepen knowledge in the field of mechanochemical synthesis of amphiphilic copolymers.

Universal properties of branched copolymers in dilute solutions

We analyze the universal conformational properties of complex copolymer macromolecules, based on two topologies: the rosette structure containing fc linear branches and fr closed loops grafted to the central core, and the symmetric pom-pom structure, consisting of a backbone linear chain terminated by two branching points with functionalities f. We assume that the constituent strands (branches) of these structures can be of two different chemical species a and b. Depending on the solvent conditions, the inter- or intrachain interactions of some links may vanish, which corresponds to Θ-state of the corresponding polymer species. Applying both the analytical approach within the frames of direct polymer renormalization and numerical simulations based on the lattice model of polymer, we evaluated the set of parameters characterizing the size properties of constituent parts of two complex topologies and estimated quantitatively the impact of interactions between constituent parts on these size characteristics.

Self-Organization of Macromolecules of Block Copolymers of Poly-2-alkyl-5,6-dihydrooxazines in Aqueous and Water–Salt Solutions

Self-Organization of Macromolecules of Block Copolymers of Poly-2-alkyl-5,6-dihydrooxazines in Aqueous and Water–Salt Solutions

Density Fluctuations Inside an Individual Polymer Coil.

More than five hundred images of individual macromolecules of random styrene-butadiene copolymers and styrene-isoprene block copolymers dissolved in a polystyrene matrix were analyzed. The presence of density fluctuations inside the macromolecular coil has been established. Within the framework of the model of harmonic oscillations, the radial distribution of such density fluctuations is estimated.

Properties in Langmuir Monolayers and Langmuir-Blodgett Films of a Block Copolymer Based on N-Isopropylacrylamide and 2,2,3,3-Tetrafluropropyl Methacrylate

The amphiphilic block copolymer poly(N-isopropylacrylamide)-Ge(C6F5)2-poly(2,2,3,3-tetrafluoropropyl methacrylate) was prepared by the reaction of chain transfer to bis-(pentafluorophenyl)germane during the polymerization of N-isopropylacrylamide and the subsequent postpolymerization of isolated functional polymers in 2,2,3,3-tetrafluoropropyl methacrylate. The conversion of the block copolymer was 68% and the molecular weight of the sample was 490,000 g/mol. The colloidal chemical properties of Langmuir monolayers and Langmuir-Blodgett films of synthesized block copolymer have been studied. For comparison, a functional polymer, namely, poly-N-isopropylacrylamide with terminal -Ge(C6F5)2H group, was synthesized and studied. The concentrations of spreading solutions were selected and the effect of subphase acidity on the formation of monolayers of macromolecules of the block copolymer was studied. It was found that regardless of the acidity of the subphase, high pressure of fracture of films are characteristic of monolayers of collapse pressures πmax = (48-61) mN/m. The morphology of the Langmuir-Blodgett films of functional polymer exhibit isolated elongated micelles with high densities in the form of "octopus" on the periphery of which there are terminal hydrophobic groups. For the Langmuir-Blodgett film of block copolymer, a comb-like structure is observed with characteristic protrusions.

Copolymers of acrylic acid with 2-hydroxyethyl methacrylate as carriers of two tuberculostatics: Synthesis, properties in solutions, drug release

Polymeric carrier for combination therapy of tuberculosis, namely low molecular weight reactive copolymer of acrylic acid with 2-hydroxyethyl methacrylate (AA-co-2-HEMA) with two types of functional groups along the chain has been synthesized. Characteristic features of radical copolymerization were studied and the relationships between the synthesis conditions and the composition, microstructure, and molecular characteristics of the copolymers were established, that is of fundamental interest. The behavior of copolymer macromolecules in aqueous salt solutions was analyzed. A tuberculostatically active derivative of AA-co-2-HEMA containing the amikacin antibiotic and the monofluoroquinolone ciprofloxacin was synthesized. The target multiunit copolymer containing two tuberculostatics with different effect against tuberculosis mycobacterium exhibits high anti-tuberculosis activity. It is characterized by a gradual release of the drugs from the polymer form and is very promising for use in combination therapy of tuberculosis.

Functionalized styrene-butadiene copolymers based on improved metal-alcoholate systems

A method for preparing functionalized styrene-butadiene copolymers on a new initiating system, which is a modifier consisting of a mixed sodium-calcium alkoxide of oxypropylated aniline dissolved in ?-methylstyrene and n-butyllithium has been developed. It was revealed that the lowered content of calcium ions makes it possible to obtain a modifier without colloidal fine-dispersed sludge, which negatively affects the operation of equipment in the industrial production of rubbers. The high initiation activity on lithium amides promoted a high conversion of monomers and a good stereoregulating ability of the 1.2-unit content of the butadiene part of the copolymer macromolecule, amounting to 66-68 wt%. The addition of a reactive compound to the end of the "living" polymer chain, stannous tetrachloride, improves the technological properties estimated by the Mooney viscosity, which increased by 5 units. It was shown on the example of prototypes of rubber mixtures, the polymer base of which was functionalized styrene-butadiene rubbers, that they are characterized by a sufficiently high rate of vulcanization, and in terms of technological, elastic and strength properties, the samples are identical with the foreign analogue NS-616, in terms of abrasion resistance they surpass the imported analogue by 20%, in resistance to crack growth by 36% was shown. The rubber mixture based on functionalized rubber was characterized by better adhesion on ice. The use of functionalized rubbers instead of serial rubber has little effect on tire rolling losses. A slight decrease in tan ? values at 0 °C for rubbers based on functionalized rubbers was noted, which can be compensated for by adjusting their microstructure and requires additional research.

Получение сополимера аллилового эфира салициловой кислоты со стиролом и исследование его антигрибковых свойств

The reactions of radical copolymerization of the allyl ester of salicylic acid with styrene were carried out and their patterns and products were studied. The Feinemann-Ross method was used to determine the constants of the relative activity of the copolymers (r1 = 0.02 and r2 = 9.6) and the parameters of the microstructure of the obtained copolymers. It was found that with an increase in the styrene content from 10 to 90 mol. % in the initial mixture of monomers, the average length of microblocks consisting of styrene units increases from 2.07 to 87.4, the length of microblocks of allylsalicylate units practically does not change, and the Harvurd constants decrease from 61.60 to 2.26. The results of studying the composition and structure of styrene and allyl salicylate copolymer samples under various conditions, as well as the values of the copolymerization constants and microstructure parameters, show that the copolymer macromolecules have a statistical structure, include allylsalicylate fragments and styrene microblocks. Studying the antifungal properties, it was found that the investigated copolymer of allyl ester of salicylic acid with styrene possesses such properties. Micromycetes such as Aspergillus niger, A.ochraseus, Penicillium cuclopium, Cladosporium herbarium, Fusarium moniliforme and F.oxysporium were used as test cultures.

ACYLATION OF THE ANHYDRITE-CONTAINING COPOLYMERS WITH VINYL CARBINOL FOR PREPARATION OF PHOTOSENSITIVE MATERIALS

By copolymerization of cycloalkyl-substituted methylenedioxolanes with maleic anhydride the copolymers, which were subjected to acylation reactions with vinyl carbinol were obtained. It was revealed that as a result of the reaction, the copolymers with various degrees of etherification were obtainedIt found that the obtained etherified copolymers exhibited various UV sensitivity depending on the degree of etherification. It revealed that the availability of highly absorbing fragments such as allyl and carbonyl groups in macromolecules of the etherified copolymers provides these polymers, along with high light-sensitivity, with film-forming properties and good adhesion to quartz substrate.

Synthesis of chitosan and N-vinylimidazole graft-copolymers and the properties of their aqueous solutions

The aim of this work is to synthesise chitosan and N-vinylimidazole graft-copolymers of various compositions and to study the properties of their aqueous solutions.Chitosan and N-vinylimidazole graft-copolymers were obtained by solution polymerisation in the presence of a ceric ammonium nitrate redox initiator. The synthesised graft copolymers were characterised by FTIR to determine their compositions and the grafted side chains of poly-N-vinylimidazole were characterised by gel permeation chromatography to determine their molecular wights and polydispersity indices. It was established that the obtained products are characterised by high values of yield and grafting efficiency and low values of the polydispersity index. It was found that when the content of the N-vinylimidazole links is above 57 wt%, the synthesised graft copolymers are water-soluble. Aqueous solutions of the obtained copolymers were characterised using dynamic light scattering, transmission electron microscopy, and laserDoppler microelectrophoresis. The study showed that macromolecules of graft copolymers in aqueous solutions have stimuli-sensitive properties with respect to the medium reaction and at a concentration above 10–2 wt% are characterised by a tendency to self-association forming core-crown aggregates, the geometry of which depends on the molecular masses of the grafted chains. Associates of macromolecules in solutions are characterised by positive values of the electrokinetic potential, the values of which also depend on the medium reaction. Thus, it was found that the ceric ammonium nitrate initiator allows obtaining chitosan and N-vinylimidazole graft-copolymers showing stimuli-sensitive properties in aqueous solutions and prone to self-association at concentrations above 10–2 wt%.

Formation of a Hollow Core in Dendrimers in Solvents

AbstractDendrimers are perfect tree‐like radially symmetric macromolecules with regular branching. Due to their architecture, dendrimers possess a set of unique properties, including high penetrating ability and a large number of functionalizable terminal groups. Practical use of dendrimers as delivery agents or nanoreactors in many cases involves a free space in a dendrimer interior. The question about presence of a hollow core (a cavity) inside the dendrimer molecule placed in a solvent attracts interest of researchers since the discovery of dendrimers. This review presents a rigorous discussion on the dendrimer structure in solution. The main objective is to draw attention to the difference in the structure of homopolymer and copolymer dendrimers. Theoretical studies typically consider homopolymer dendrimers (with similar inner and terminal segments), whereas experiments often examine dendrimers with massive terminal groups which chemical structure is different from the structure of the dendrimer inner groups. In the latter case, dendrimer is a copolymer macromolecule, and its conformation can depend on additional factors, such as solvent selectivity, or poor compatibility of terminal and core groups. The influence of these factors can lead to the formation of a region with a lower polymer density inside the dendrimer.

FORMATION OF NICKEL NANOPARTICLES IN SOLUTIONS OF A HYDROPHILIC GRAFT COPOLYMER

A graft copolymer of poly(vinyl alcohol) and polyacrylamide (PVA-g-PAAm) with interacting main and grafted chains was synthesized by radical matrix polymerization of PAAm from the PVA backbone in an aqueous medium. Its basic molecular parameters including the number and length (molecular weight) of grafts were determined using elemental analysis, DTGA and viscometry. The copolymer macromolecules formed special monomolecular micelles of elipsoidal shape and length ~18-64 nm in aqueous solutions due to the formation of intramolecular polycomplexes between the main and grafted chains. This copolymer was used as a hydrophilic matrix for the in situ synthesis of nickel nanoparticles (NiNPs) in aqueous solutions.On the basis of UV-Vis spectroscopy, an original and simple method for monitoring the kinetics of the formation and yield of metal nanoparticles in systems in which a surface plasmon resonance band does not appear has been proposed and implemented. Using this approach, the kinetics of borohydride reduction of Ni-salt to NiNPs in pure water and PVA-g-PAAm solutions was studied depending on the concentrations of Ni-salt and copolymer matrices. An increase in the initial rate of accumulation and yield of NiNPs with an increase in the concentration of Ni-salt and a decrease in both parameters in copolymer solutions in comparison with pure water was established. At the same time, the accumulation rate and NiNP yield in a complex way was depended on the matrix concentration that was determined by the ratio of such factors as a decrease in the diffusion rate of NaBH4 molecules in copolymer solutions and the accumulation of Ni2+-ions in matrix particles due to complexation with active chemical groups at the first stage of reduction process. The morphology and main structural elements of the NiNPs/PVA-g-PAAm composition were revealed using TEM. It was shown that the in situ synthesis of NiNPs in copolymer matrices was accompanied by the “detachment” of PAAm grafts from the main PVA chains and led to the appearance of two new structures, such as “hairy coils” and “hairy rods”, containing small spherical NiNPs (d~0,5–12,0 nm) in isolated and chain states, respectively. The appearance of the latter structures was explained by the formation of coordination complexes of Ni2+-ions with active groups of both PVA and PAAm chains at the first stage of the reduction reaction.

Synthesis of grafted polybutyl acrylate copolymer on fish collagen

Increasingly, scientists are turning to the study of marine, or fish, collagen, which is increasingly replacing collagen of terrestrial animals, due to the fact that it is hypoallergenic, since it is 96% identical to human protein. Materials based on fish collagen have a number of advantages over their analogue of animal origin: it is not a carrier of infectious diseases of animals transmitted to humans, it has a greater structural similarity to human collagen, which provides a higher level of biocompatibility. Materials based on collagen copolymers with synthetic monomers are promising. The use of hybrid materials also helps to reduce the consumption of non-renewable natural resources. Synthesis of grafted collagen copolymers with polybutyl acrylate was carried out at azobisisobutyronitrile initiation and triethyl borane – oxygen system initiation under comparable conditions under intensive stirring of aqueous solution dispersion of collagen and butyl acrylate. After the synthesis, the aqueous and organic phases of the reaction mixture were analyzed by composition and molecular weight parameters using infrared spectroscopy and size-exclusion chromatography. Changes indicating the formation of a copolymer are observed in the copolymer isolated from the aqueous phase, more pronounced in the triethyl borane – oxygen system. It is assumed that the formation of copolymer macromolecules for azobisisobutyronitrile and organoelement initiator takes place according to different schemes. Schemes for the formation of copolymer macromolecules for AIBN and an organoelement initiator are proposed. Only polybutyl acrylate is present in the organic phase. Biological studies were carried out for fungal resistance and bactericidal activity of the obtained copolymers.

A theoretical estimate on the probability of the formation of a self-avoiding copolymer macromolecule

An infinitely long copolymer chain has been chosen as a directed self avoiding walk on a cubic lattice to understand the thermodynamics of the formation of a semi-flexible copolymer chain; and this linear copolymer chain is made of four different types of the monomers. A method of the recursion relations is used to solve the proposed model analytically for the semi-flexible self-avoiding copolymer chain; and it has been shown that the probability of the formation of a self-avoiding semi-flexible copolymer chain is independent of the stiffness of the copolymer chain. The result so obtained is a distinct result from our earlier findings on the formation of the Gaussian semi-flexible copolymer chain and the Gaussian chain is made up of these four monomers, [P. K. Mishra, 2020 J. of Adv. Appl. Sci. Res. 2(4) 1-8]. The distinction in the thermodynamics of the self-avoiding copolymer chain from the Gaussian copolymer chain has been further confirmed on the basis of calculations on an average number of different types of the bonding in the copolymer chain.

Copolymers of Methyl Acrylate and Vinylazoles: Synthesis, Thermolabile Properties, and Grafting of Polyamine Chains

New copolymers of methyl acrylate with 1-vinylimidazole, 1-vinyl-1,2,4-triazole, and 4-vinyl-1,2,3-triazole are synthesized by radical copolymerization. It is shown that the reactivity ratios for methyl acrylate and 1-vinylimidazole are 0.83 ± 0.09 and 0.25 ± 0.02, for methyl acrylate and 1-vinyl-1,2,4-triazole are 1.0 ± 0.04 and 0.27 ± 0.01, and for methyl acrylate and (4-vinyl-1Н-1,2,3-triazolyl)-methyl pivalate are 0.56 ± 0.03 and 2.90 ± 0.20, respectively. The behavior of the copolymers in aqueous media and their thermoresponsive properties are studied by potentiometric titration and dynamic light scattering. Copolymer macromolecules occur in aqueous solutions in the form of large associates the fraction of which increases upon heating; in some cases, an insoluble phase is formed. It is found that the copolymers with the grafted oligopropylamine moieties containing N-vinylazole units can interact with the DNA oligonucleotide, stimulating their research as agents for the delivery of nucleic acids to living cells.

The Effect of the Synthetic Procedure of Acrylonitrile-Acrylic Acid Copolymers on Rheological Properties of Solutions and Features of Fiber Spinning.

The influence of introducing acrylic acid (AA) into the reaction mixture with acrylonitrile at the synthesis of copolymers by free-radical polymerization (FRP) and radical polymerization with reversible addition–fragmentation chain transfer (RAFT) on the rheological properties of their solutions in dimethyl sulfoxide, as well as on the capability to spin fibers by the mechanotropic method, is analyzed. The influence of AA dosing conditions on the rheological properties of the solutions in the concentration range above the crossover point was not revealed. In the case of RAFT synthesis, the rheological properties differ distinctively in the high concentration region that is expressed by unusual viscoelastic characteristics. Dilute solution viscometry revealed the influence of the comonomer loading order on the interaction intensity of the copolymer macromolecules with a solvent, which is more pronounced for samples synthesized by FRP and can be associated with the copolymers’ molecular structure. Fiber spinning from solutions of polyacrylonitrile and its copolymers (PAN) synthesized by the RAFT method was not able to achieve a high degree of orientation drawing, while for polymers with a wider molecular weight distribution synthesized by FRP, it was possible to realize large stretches, which led to high-quality fibers with strength values up to 640 MPa and elongation at a break of 20%.

Reversible inhibition in the formation of copolymers based on alkyl (meth)acrylates with vinyl butyl ethers under compensation of the active monomer depending on their nature when initiated by the triethylborane–oxygen system

Compensatory (or compensation) copolymerization of alkyl (meth)acrylates (AMA) with boiling vinyl butyl ether (VBE), initiated by the system of triethylborane (TEB)–oxygen, has been studied. The obtained data indicate a partial formation of copolymer macromolecules with close to an alternating structure, according to the reversible inhibition mechanism, along with a copolymer formation on the scheme of conventional bimolecular termination. Specific features of used acrylic monomers have been revealed. Copolymers of methyl methacrylate (MMA) and VBE were applied as macroinitiators for block-copolymer syntheses when adding new portions of butyl acrylate (BA).

A model for producing polymer stabilizers of composites with a given macromolecule composition

An attempt has been made to obtain a working technological formula that regulates the addition of comonomer over time, which ensures the synthesis of a copolymer macromolecule with a constant composition and, accordingly, with predicted properties of both the copolymer and its modified porous composite materials. Mathematical modeling is based on the theory of the kinetics of copolymerization, which takes into account the reactivity of monomers by means of copolymerization constants of reacting comonomers. The starting base was the kinetics of the copolymerization of two comonomers, significantly differing in their reactivity, which required a sequential, stepwise supply of a less reactive monomer to the reaction medium with a more active monomer. This technological technique contributes to maintaining the constancy of the initial ratio of comonomers and, accordingly, the synthesis of a copolymer with a constant composition, structure and properties. The dependence of the sequence of supply of comonomer to the reaction medium required the introduction of a generalized effective binary copolymerization rate coefficient. To find the generalized coefficient of the copolymerization rate, the operation of logarithm was performed and the current expression of the dependence of the concentration change of the more active monomer in time in a linear form was translated. This mathematical technique made it possible to use software to process reference information to obtain the necessary coefficients for the working formula. As a result of mathematical modeling using the basic principles of binary copolymerization, the law of effective masses, and the least squares method, a working formula is obtained that allows one to regulate the given introduction of a less active monomer into the reaction medium in time. The model is analyzed using background information, the basic concepts of binary copolymerization and can be used in technological calculations when producing copolymers with specified characteristics in composition and structure.

Amphiphilic Copolymers of Acrylic Acid and n-Butyl Acrylate with the Predetermined Microstructure: Synthesis and Properties

Features of the synthesis of n-butyl acrylate copolymers with acrylic acid in 1,4-dioxane by free radical reversible addition-fragmentation chain transfer (RAFT) polymerization mediated by symmetric trithiocarbonates are considered. It is shown that the living mechanism of polymerization is realized in the studied systems. The chemical nature of the RAFT agent dictates different chain microstructures (random block or random) of the copolymers. The effect of chain microstructure on the properties of the copolymers containing about 90 mol % of acrylic acid units is studied by differential scanning calorimetry, contact angle measurements, turbidimetry, potentiometric titration, and dynamic light scattering. It is demonstrated that all the copolymers in the solid phase have similar properties: a single glass transition temperature close to the glass transition temperature of polyacid and a good water wettability. In dilute aqueous solutions, the properties of the copolymers are different: at the inherent pH, random copolymer macromolecules form large associates, while random block copolymers are dispersed into individual coils or micelles. All the copolymers are weaker polyacids compared with PAA; the random block copolymers are characterized by the compaction of macromolecules at small degrees of ionization. Our studies provide evidence that reversible addition-fragmentation chain transfer polymerization is an efficient tool for the targeted insertion of nonpolar units into a polyelectrolyte chain and it can be used for the fine-tuning of its properties.

Chemical modification of functional copolymers

The possibility of chemical modification of thermally-stable functional copolymers of 1-vinyl-1,2,4-triazole with vinyl acetate of various compositions synthesized under conditions of free-radical polymerisation in the presence of azobisisobutyronitrile was studied. Modification of the copolymers was carried out by alkaline hydrolysis; as a result, new copolymers containing vinyl triazole and vinyl alcohol units in the macromolecules were obtained. The structure, composition, physical and chemical properties of the copolymers were determined using elemental analysis, infrared spectroscopy and thermogravimetric analysis. With an increase in the number of vinyl alcohol units in the copolymer from 25 to 87 mol %, a nearly twofold reduction in the intrinsic viscosity of the copolymers was observed. The copolymers, which exhibit dielectric properties, are characterised by electrical conductivity of the order of Ш 14-10-15 S/cm. According to thermogravimetric analysis data, the copolymers are resistant to thermooxidative degradation up to 270-290 °C depending on the composition. The introduction of a vinyl alcohol fragment into the structure of copolymer macromolecules contributed to the improvement of their fibre- and film-forming properties - that is, fibres and transparent elastic films with good adhesion to various metal surfaces can be formed from solutions of modified copolymers based on 1-vinyl-1,2,4-triazole.