Polymer Science Series A

Published by MAIK Nauka/Interperiodica
Online ISSN: 1555-6107
Print ISSN: 0965-545X
Publications
Soft polymeric nanomaterials were synthesized by template-assisted method involving condensation of the poly(ethylene oxide)-b-polycarboxylate anions by metal ions into core-shell block ionomer complex micelles followed by chemical cross-linking of the polyion chains in the micelle cores. The resulting materials represent nanogels and are capable of swelling in a pH-dependent manner. The structural determinants that guide the self-assembly of the initial micelle templates and the swelling behavior of the cross-linked micelles include the block ionomer structure, the chemical nature of metal ions, the structure of the cross-links and the degree of cross-linking. The application of these materials for loading and release of a drug, cisplatin, is evaluated. These cross-linked block ionomer micelles have promise for delivery of pharmaceutical agents.
 
Polyethylene glycol derivatives, such as block copolymers of polyethylene glycol and diacyllipids (for example, phosphatidylethanolamine) are widely used for surface modification of various pharmaceutical carriers in order to impart them longevity in the body. To make polyethylene glycol detachable from the surface of pharmaceutical carrier and facilitate the interaction of the carrier with target cells when in pathological zone, we have prepared a set of polyethylene glycol-phosphatidylethanolamine block copolymers with the pH sensitive hydrazone bond between polyethylene glycol and phosphatidylethanolamine, which destabilizes at lowered pH values typical for tumors and inflammation zones. We have demonstrated that the stability of the hydrazone bond at normal physiological pH (7.4) as well as the rate of its hydrolysis at pH 6 and below strongly depend on the type of substitutions at this bond. Using aliphatic and aromatic aldehydes and ketones, polyethylene glycol-phosphatidylethanolamine block copolymers were prepared with different stabilities and degradation rates, which can be useful in constructing stimuli-sensitive pharmaceutical carriers.
 
A comparative analysis of phase transitions in diols with different chain lengths, (CH2)44(OH)2 and (CH2)22(OH)2, was performed using differential scanning calorimetry. The use of temperature hysteresis made it possible to reveal a number of new effects associated with the specifics of first-order phase transitions. The parameters of transitions were quantitatively analyzed in terms of the self-consistent field theory for diffuse (A-shaped) first-order transitions.
 
The molecular properties of a number of new poly(naphthylimides) derived from naphthalene-1,4,5,8-tetracarboxylic dianhydride and bis(naphthalic anhydrides) have been studied. On the basis of hydrodynamic studies of the polymers at various stages of their thermal degradation in 96% H2SO4 and thermogravimetric measurements, the hydrolytic stability and thermooxidative resistance of the polymers have been compared. A correlation between the experimental data and the chemical structure of molecular chains has been established.
 
Poly(N-acryloyl-11-aminoundecanoic acid) samples are synthesized in monomer solutions occurring in both micellar and nonmicellar states. It is shown that polymeric ionogenic surfactants of various molecular masses can be prepared through variation in the concentration of a polymerizable surfactant or in the ionic strength of a solution. The polymer of interest is investigated in detail via the methods of molecular hydrodynamics (viscometry, isothermal diffusion, and velocity sedimentation), dynamic light scattering, GPC, and scanning probe microscopy. The solubility of the polymer in various solvents is examined in detail, and the tendency of this polymer toward association in DMF solutions is discovered. The equilibrium rigidity of macromolecules, which is characterized by the Kuhn segment length A = 100 × 10−8 cm, and the effective hydrodynamic radius are determined in a dioxane-cyclohexanol mixed solvent.
 
The optical, electro-optical, and dynamic characteristics of poly(N-acryloyl-11-aminoundecanoic acid) in organic solvents and of the sodium salt of its monomer in water were studied via the methods of flow birefringence, equilibrium and nonequilibrium electric birefringence, and dynamic light scattering. It is shown that, in aqueous solutions, the monomer forms coarse particles of both symmetric and asymmetric shapes. The linear dimensions of these particles are estimated from the data of translational and rotational diffusion. Polymer macromolecules in organic solvents feature negative anisotropy of optical polarizability. Contributions of optical microform and macroform effects to the observed flow birefringence are analyzed in detail. The intrinsic optical anisotropy of the monomer unit of the polymer, which correlates well with the corresponding values for comb-shaped polymers of a similar structure, is estimated. It is shown that polymer molecules lack marked intrinsic permanent macromolecular dipoles and that electric birefringence in their solutions is associated with macroscopic induced dipole moments that appear during orientation of the dipole moments of polar groups in side chains of the polymer under application of an electric field.
 
The structure of pluronic F-127 and its complexes with tetraphenylporphyrin has been studied by SAXS and WAXS techniques. It has been shown that the samples prepared via evaporation of chloroform and aqueous solutions of pluronic and its mixtures with tetraphenylporphyrin have a semicrystalline layered structure with the crystalline phase composed of poly(ethylene oxide). The identity period of layers in the samples prepared from the aqueous solution of pluronic has been found to be larger than that in the samples prepared from chloroform solutions of the polymer. This result may apparently be explained by a more pronounced hydration of the samples prepared by the former method. The presence of tetraphenylporphyrin in the samples has an insignificant effect on the parameters of the crystalline and layered structures of pluronic. When the tetraphenylporphyrin content is not larger than its solubilization limit with pluronic, tetraphenylporphyrin concentrates in the amorphous layers of pluronic in the noncrystalline finely dispersed state.
 
The evolution of fundamental concepts concerning the mechanisms of plastic deformation in solid polymers, crystals (both glassy and semicrystalline) over the recent five decades has been reviewed. The most effective approach to the description of cold plastic deformation is a gradual drift away from the chain straightening mechanism as a limiting kinetic stage of the process (or, in other words, from the picture of the rubbery character of deformation) to concepts that are characteristic of the deformation physics of nonpolymer solids, primarily metals. Various nonpolymeric mechanisms, such as nucleation and growth of dislocations in polymer crystals, formation and evolution of short-scale undeveloped shear transformations in glasses, and mutual deformation constraints of amorphous and crystalline phases in semicrystalline polymers, are introduced in polymer science. An analysis of the published data shows that deformation in solid polymers is undoubtedly accompanied by chain straightening, but, in most cases, this process does not control the overall kinetics of plasticity, at least at small and moderate strains. In glassy polymers, conformational chain rearrangements are not going directly but proceed as shape fitting of macromolecule coils to short-scale shear transformations that serve as active sites of plasticity. The chain character and flexibility of macromolecules have a slight effect on the nucleation of the above transformations. The development of local shear at the early stages of loading is the thorniest stage of deformation. Problems concerning the joint development of polymer and nonpolymer processes during deformation of macromolecular solids and the specific features related to the polymer structure of macromolecules are discussed.
 
It is shown that the amphiphilic diblock copolymers poly(N-vinylpyrrolidone-2,2,3,3-tetrafluoropropyl methacrylate) can be prepared through the reaction of chain transfer to bis(pentafluorophenyl)germane during the polymerization of N-vinylpyrrolidone and the subsequent postpolymerization of isolated functional polymers in 2,2,3,3-tetrafluoropropyl methacrylate. The dilute-solution behavior and self-organizing ability of functional polymers based on poly(N-vinylpyrrolidone) containing end bis(pentafluorophenyl) groups and of amphiphilic diblock copolymers formed on their basis are studied via the methods of static and dynamic light scattering and viscometry. Surface properties at the interface of the films are estimated through the wetting technique.
 
By the examples of chemically similar styrene-acrylonitrile and styrene-methacrylonitrile systems, substantially different mechanisms of TEMPO-mediated copolymerization have been theoretically predicted and experimentally verified. Living copolymer-TEMPO adducts capable of thermal decomposition and polymerization reinitiation via the pseudoliving mechanism predominantly form in the first system. The reaction proceeds under the steady-state regime and is characterized by the living growth of M n of the copolymer with conversion. In the second system, the probabilities of formation of living and dead macromolecules are equal. Therefore, the living growth of M n of the copolymer ceases and the reaction passes to the conventional copolymerization regime.
 
Two alternating narrow band gap (NBG) copolymers derived from 5,11-di(N-9-heptadecanyl)-indolo[3,2-b]carbazole (ICZ) and 4,7-di(thien-2-yl)-2′,1′,3′-benzoselenadiazole (DSeBT) or 4,7-di(thieno[3,2-b]thien-2-yl)-2′,1′,3′-benzoselenadiazole (DTSeBT), were synthesized and named PICZ-DSeBT and PICZ-DTSeBT, respectively. The PICZ-DSeBT shows good solubility in common organic solvent, and the PICZ-DTSeBT is soluble in hot o-dichlorobenzene (ODCB) and not good soluble in chloroform, toluene etc. The chemical structure, molecular weight and fundamental physical properties of the copolymers were characterized by 1H NMR, gel permeation chromatography (GPC), cyclic voltammetry (CV), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) etc. Potential application of the copolymers to be employed as electron donor material and PC61BM ([6,6]-phenyl-C61 butyric acid methyl ester) for photovoltaic solar cells (PSCs), were investigated. PSCs based on the blends of PICZ-DSeBT/PC61BM (w: w; 1: 2) or PICZ-DTSeBT/PC61BM (w: w; 1: 2) with devices configuration as ITO/PEDOT: PSS/blend/Al, show the power conversion efficiencies (PCEs) of 1.06% and 1.52%, with the open circuit voltage (V oc) of 0.75 V and 0.70 V, short circuit current densities (J sc) of 3.45 mA/cm2 and 5.30 mA/cm2 under an AM1.5 simulator (100 mW/cm2) and the photocurrent response on-set wavelength extending up to 760 nm and 800 nm, respectively. It indicates that the NBG copolymers are viable electron donor materials for PSCs.
 
Intersolubility and interdiffusion in the oligo(3,3-bis(azidomethyl)oxetane)-oligo(3-methyl-3-azidomethyloxetane) binary system are studied. The components of the system differ in symmetric and non-symmetric positions of azide groups along the polymer chain, respectively. The chemical and conformational features ensure the ability of oligo(3,3-bis(azidomethyl)oxetane) to crystallize at temperatures of ∼50°C. The system of azidooxetane oligomers is characterized by a simple crystalline equilibrium crystal-melt. The generalized phase diagram of the binary system is constructed. The interdiffusion zones of oligomers are analyzed in detail in a wide temperature range, and a number of specific effects manifesting themselves during their intersolubility are observed. The concentration and temperature dependences of diffusion coefficients are examined, and the activation energies of diffusion are calculated.
 
For a number of new polyimides prepared from 3,5-diaminodiphenyl oxide, 2-methyl-3,5-diaminodiphenyl sulfide, and various dianhydrides of aromatic tetracarboxylic acids, the hydrolytic stability in DMF and 96% H2SO4 and the thermooxidative stability in the bulk have been studied. Hydrodynamic techniques have been employed to determine the molecular parameters of these polymers at various stages of degradation. It has been shown that the polymers under study form stable solutions in DMF but turn out to be unstable in 96% H2SO4 even at room temperature. Degradation accompanies dissolution of the polymer. The correlation between the chemical structure of polymer molecules and their hydrolytic stability in both solvents has been established. It has been demonstrated that the majority of the said polyimides are stable in the solid state at temperatures up to 400°C and marked degradation begins only above 500°C.
 
The temperature dependences of the heat capacities of hydrated acrylamide and poly(acrylamide) complexes of cobalt nitrate are studied via high-precision adiabatic calorimetry at 6 to 300–380 K. The energy of combustion is estimated via isothermic calorimetry. This evidence makes it possible to calculate thermodynamic functions C p ℴ(T), H ℴ(T) − H ℴ(0), S ℴ(T), G ℴ(T) − H ℴ(0) at 0 to 300–380 K; the standard enthalpy of combustion, ΔcH ℴ; and the thermodynamic parameters of formation, Δ f H ℴ, Δ f S ℴ, and Δ f G ℴ, of monomer and polymer complexes composed of simple compounds at 298.15 K. The results are used for the estimation of enthalpy Δpol H ℴ, entropy Δpol S ℴ, and Gibbs function Δpol G ℴ of bulk polymerization for hydrated acrylamide complexes of cobalt nitrate at 0–300 K.
 
The internal organization of star-shaped polystyrene macromolecules containing fullerene C60 as a branching center is studied via small-angle neutron scattering in deuterotoluene. Analysis of the experimental data according to the Debye-Benoit approximation and the Fourier transformation of the momentum transfer dependences of scattering cross sections for the linear PS precursor and stars is used to determine their molecular masses (9 × 103 and 5 × 104) and gyration radii (∼2.7 and ∼5.5 nm), the gyration radius of the arm (∼3.4 nm), and the average functionality of the star (5.7). The behavior of scattering cross sections for the fullerene-containing polymer on the whole is described by the law of scattering for stars with Gaussian arms (the Benoit model). However, at the local level (within one chain segment), the fullerene center exerts a specific effect on the conformation of arms. As a result, their statistical flexibility decreases and eventually the size of the star increases by ∼30%. This finding conflicts with the Daoud-Cotton theory.
 
A series of ABS plastics prepared by bulk polymerization was studied. The test samples contained almost equal amounts of PB but mostly differed in the molecular mass of a styrene-acrylonitrile copolymer. It was shown that the molecular mass of the copolymer strongly affects the rheological and mechanical properties of ABS plastics. An increase in molecular mass leads to a rise not only in the non-Newtonian viscosity of plastics but also in their yield point, storage modulus under periodic steady-state shear flow in the low-frequency plateau region, and impact strength. Quantitative correlations between these rheological and mechanical characteristics of the copolymers and their M w values were established. As opposed to homophase polymer systems, a marked increase in the shear stress has no effect on viscosity in relation to the molecular mass of ABS plastics. In the case of melts, the influence of the M w of the styrene-acrylonitrile copolymer on the rheological behavior of ABS plastics is apparently related to a change in the interaction of PB particles with the copolymer that controls the structural framework of the system. The relationship between the impact strength of the copolymer and its M W may be explained by the fact that the latter parameter influences orientational effects in crazes that arise during steady-state shear flow of ABS plastics in the solid state.
 
The occupied and accessible volumes have been calculated for 32 polyimides of various structures. The calculation data have been compared with the experimentally measured transport parameters for one polymer-various gases and one gas-various polymers systems. The correlation coefficients have been estimated as 90–98%. The transport parameters plotted as a function of the Kuhn segment are described by curves with maxima. The best transport characteristics are exhibited by polymers with Kuhn segment lengths of 60–80 Å.
 
The effect of initiation conditions on the self-sustained-wave regime of copolymerization of acetaldehyde with hydrogen cyanide has been studied. The local brittle failure in the bottom of the sample makes it possible to implement the high-velocity (detonation-like) traveling wave regime of copolymerization. The velocity of propagation of the reaction wave front achieves 1870 mm/s at an irradiation dose of 55 kGy. However, the copolymer formed in the course of preliminary irradiation at 77 K changes the properties of the solid matrix of the reagents and, at high irradiation doses, the high-velocity traveling wave regime of copolymerization degenerates. The velocity of propagation of the copolymerization wave decreases, and, at an irradiation dose of 200 kGy, it is as low as 50 mm/s. The same velocity of propagation is observed when the reaction is initiated by the brittle failure in the top of the sample.
 
Physicochemical characteristics of solvents
The ability of acetate fibers to experience spontaneous changes in their linear dimensions under the action of vapors of aprotic, amphiprotic, and protic solvents, which are widely used in scientific studies and engineering practice, has been investigated. In the vapor phase of solvents that are able to produce the lyotropic LC phase in cellulose derivatives, the phenomenon of spontaneous elongation of fibers has been discovered. This phenomenon has been observed for both cellulose diacetate and triacetate yarns, and their elongation can achieve ∼ 120–180%. In some systems, one can observe the reverse process that represents a spontaneous contraction of the sample after its self-elongation in solvent vapor. To study the above phenomena, a well-known system based on cellulose acetate and nitromethane is considered to be a reference system. The phenomenon of spontaneous elongation is proposed for use as a test for estimating the ability of the (cellulose ether)-solvent system to experience LC ordering.
 
Amplitude of harmonics at λ = 436 nm for initial and TFA vaporrtreated CDA and CTA films
The optical activity of anisotropic solutions of cellulose diacetate in nitromethane and dimethyl sulfoxide and of diand triacetate films with vitrified ordered structure has been studied. The systems under study are characterized by high specific optical rotation [α], suggesting formation of a cholesteric mesophase. The value of [α] is found to depend on the angle of rotation of the samples relative to the direction of the polarization vector of an incident light beam in the plane perpendicular to this beam (the anisotropy of optical activity). This dependence (indicatrix) shows an irregular pattern and, when plotted in Cartesian coordinates, can be described with a distorted sinusoid. The data on the resolution of indicatrices into harmonic constituents and isolation of contributions due to isotropic components and anisotropic components, each of which is determined by the structural element with the corresponding asymmetry, are analyzed.
 
A composite consisting of two nanosized biocompatible components, Acetobacter xylinum cellulose and calcium phosphate, is prepared through aggregation in an aqueous suspension. The structures of initial components and composite are investigated by the methods of X-ray and electron diffraction and electron microscopy. The mineral component consists of two crystalline phases, hydroxyapatite and whitlockite (magnesium-containing tricalcium phosphate), which are nanosized platelike crystals. The composite preserves the crystalline structures of initial calcium phosphates and cellulose. In the course of composite formation, hydroxyapatite and whitlockite crystallites are adsorbed on the surfaces of nanofibrillar cellulose ribbons. Whitlockite nanocrystals are predominantly deposited on the surface of cellulose ribbons. The mutual orientation of the surfaces of crystalline structures of cellulose and two types of calcium phosphates, hydroxyapatite and whitlockite, is analyzed by means of computer simulation, and the variants of mutual arrangement of their surfaces during formation of the interfacial boundary are suggested.
 
The state of the art in the rheology of polymer fluids (polymer solutions and melts) and filled composites is reviewed. This review includes two parts: analysis of the basic principles for the construction of rheological constitutive equations in terms of the continuum mechanics and finding correlations between the rheological characteristics and molecular structure of polymers on the basis of molecular models. Possible approaches to the formulation of constitutive equations are discussed. Special attention is focused on the correct selection of the form of the elastic potential for rubbery deformations induced under the flow of polymer fluids. The use of a power-law potential leads to the best results. To gain unequivocal results and minimize the number of free constants, viscoelastic characteristics of polymer fluids should be described in terms of a continuous relaxation spectrum as a power-law function limited by the maximum relaxation time. To solve the boundary problems by the selected constitutive equation, analysis of the dynamic stability is required, because the combination of viscosity and elasticity controls the limits of flow upon shear and tensile. Deformation can also lead to changes in the phase state of a polymer system. Furthermore, correct formulation of the boundary conditions is necessary because, in many cases, polymer fluids and, in particular, filled materials tend to efficient slip along walls. The existing molecular models adequately describe the characteristics of monodisperse polymers; however, on passing to polydisperse polymers, the additional use of semiempirical approaches is required. The modern level of experimental studies allows test measurements over a wide range of deformation rates, frequencies, and temperatures. However, in this field, the mainstream tendency in experimental studies is concerned with hybrid methods, which combine direct rheological measurements with optical observations of local structure and its evolution in the material. In this case, various physical principles of measurements are applied. In recent years, much interest has been focused on studying polymer compositions containing nanosized fillers, which are able to produce their structures in melt.
 
The stability of insoluble polyelectrolyte complexes formed by various carboxyl-containing polyanions with a positively charged partner—a linear polycation or protein—has been studied by means of turbidimetric titration. In most cases, acidification of the reaction medium leads to a significant strengthening of complexes against the action of the added salt in neutral or weakly acidic media. The data concerning the effect of the chemical nature of polymer components, the degree of polymerization, the density of charge, and the structure of their chains on the pH-dependent profiles of complex dissociation provide evidence that this effect is related to stabilization of the polyelectrolyte complex through the system of hydrogen bonds formed by carboxyl groups of a partially charged polyanion incorporated into the complex. Owing to a sharp and reversible change in the stability of systems at a pH and ionic strength of solution that are favorable for functioning of biopolymers (proteins, enzymes, antibodies, and nucleic acids), polycarboxylate polyelectrolyte complexes offer promise for solving practically important problems, for example, in biotechnology for separation of biological mixtures.
 
In this study, the interaction between poly(styrene sulfonic acid), polyacrylic acid, poly(meth-acrylic acid), poly(L-glutamic acid), poly(vinyl sulfate), and ternary copolymer of styrene with maleic anhydride and methacrylic acid (3: 2: 1), as well as DNA with lipid vesicles composed of zwitterion (electroneutral) lipid phosphatidylcholine, has been investigated. The methods of centrifuge ultrafiltration and dynamic light scattering reveal that, at pH 4.2, all polyacids under study are effectively adsorbed on the phospholipid membrane. The polymer-membrane complex is stabilized by hydrogen bonds and hydrophobic interactions in addition to electrostatic bonds. Even though, to a greater or lesser extent, all polyacids are capable of undergoing adsorption on the membrane in a slightly acidic medium, their effect on the membrane permeability is substantially different and is correlated with the ability of a polymer to form multiple interactions with phospholipid molecules. Poly(acrylic acid), poly(methacrylic acid), poly(styrene sulfonic acid), and the ternary copolymer of styrene with maleic anhydride and methacrylic acid can produce the membrane pores that are permeable to low-molecular-mass compounds. At the same time, poly(L-glutamic acid), poly(vinyl sulfate), and DNA exert no effect on the membrane permeability, although they are sorbed on the membrane surface.
 
Poly(amido acids) with main-chain metal-binding ligands methylene-bis(anthranilic acid) and their linking fragments of a widely varied structure have been synthesized. The chemical structure of poly(amido acids) that affect the luminescence of Tb3+ and Eu3+ ions and interact with them is studied, and the mechanism of this effect is advanced.
 
Characteristics of acid modifiers 
Degree of substitution and solubility of XX700 chitosan derivatives depending on the type and content of modifier 
Stability of foams from XX700 COS solutions 
Interrelationship of solution composition, surface tension, and foam stability 
The synthesis and surface properties of aqueous solutions of salts of chitosan and di-, tri-, and oligo(ethylene oxide) sulfonic acids are described. It is shown that, unlike chitosan acetate solutions, the solutions of chitosan oligo(ethylene oxide) sulfonate feature a pronounced surface activity and good foamforming properties; this makes the latter compounds candidates for use in foam technologies of fiber and textile finishing.
 
Polyaniline coatings on the surface of the macroporous silica have been prepared by oxidative polymerization via protonation of aniline by poly(sulfonic acids): poly(p,p′-(2,2′-disulfonic acid)diphenyle-neisophthalamide and poly(p,p′-(2,2′-disulfonic acid)diphenyleneterephthalamide. Two variants of modification have been studied: namely, the polymerization of aniline carried out in the presence of the preliminarily silaminated glass covered by poly(sulfonic acid) and the modification of silaminated glass by preformed complexes of poly(p,p′-(2,2′-disulfonic acid)diphenylenephthalamide-polyaniline. In both cases, the even polyaniline-containing polymer coating with a thickness of ∼3 nm is formed on the support surface. Sorbents containing the poly(p,p′-(2,2′-disulfonic acid)diphenylenephthalamide-polyaniline complex are efficient for isolation of DNA from mixtures of biopolymers.
 
(Contd.) 
Sequences of tryptic peptides from bovine serum albumin used for comparison of predicted and experimental re- tention times 
Experimental data on the separation of synthetic and natural peptides are presented as treated in terms of the separation model proposed by the authors, which allows for the chain connectivity of amino acid residues and the cooperative character of their interaction with the surface. It was shown that the model accurately predicts the separation of peptides with identical amino acid contents and different sequences of units in the chain. The differences in the sequence may be permutation of amino acid residues and the presence of terminal groups, amino acid isomers, or mirror sequences in the chain. The separation model was used to predict the retention times of peptides prepared via the enzymatic hydrolysis of E. coli proteins and bovine serum albumin with trypsin. It was shown that in general the model accurately explains the array of experimental data on the separation of such peptides, thus being the first successful attempt to relate the chain sequence to the retention volume.
 
Polyionenes composed of oxyethylene and aliphatic hydrocarbon units were studied by differential scanning calorimetry, wide-and small-angle X-ray scattering, and dielectric spectroscopy. These polymers are characterized by the variation of T g with the concentration of ionic centers. Polyionenes with short ethylene oxide segments are amorphous; however, as the average number of monomer units in the oxyethylene segments increases to 20, a crystalline structure typical of poly(ethylene oxide) is formed. Oxyethylene-aliphatic polyionenes are microphase-separated systems. Polyionenes from this series are characterized by a high ionic conductivity, which increases with an increase in the concentration of ionic sites—the conductivity at room temperature is 10−5–10−4 Ω−1 cm−1. By means of acoustic spectroscopy, it was found that the isotherms of the ultrasound absorption (frequency domain) and ultrasound speed had two dispersion regions. The mechanism of the dispersions was associated with the softening of the quasi-lattice produced by cationic sites and with the motion of chain segments connecting these sites, The speed of sound in polyionene is abnormally high (1800–2100 m/s) for polymers, a result which is due to a high level of intermolecular interactions.
 
The nature of active centers and the specific features of the spontaneous polymerization of acrylamide in glycerol in the range 300-77 K have been studied. Glycerol activation is needed for polymerization. At this stage, active intermediate species are formed and stabilized under the action of photo-and γ radiation. Intermediate species are hydroperoxide compounds resulting from the sensitized (through technical traces) photolysis (or radiolysis) of glycerol. The decomposition of hydroperoxides into radicals on addition of finely dispersed acrylamide powder into the activated glycerol yields primary acrylamide radicals that initiate the growth of polymer chains.
 
Enthalpies and effective rate constants of the free- radical polymerization of acrylamide monomers at 60°C and the temperatures of glass transition T g and melting T m of the polymers
Water-soluble acrylamide monomers N-(hydroxymethyl)acrylamide, N-(hydroxymethyl)methacrylamide, N,N-diethanolacrylamide, N,N-diethanolmethacrylamide, N,N-methylethanolacrylamide, and N,N-methylethanolmethacrylamide have been synthesized and characterized. The kinetics and thermodynamics of the free-radical polymerization of these monomers and of the model compounds N-isopropylacrylamide and acrylamide have been studied by the methods of isothermal and scanning calorimetry. The structure and the solubility of the said polymers in water and organic solvents have been investigated and their molecular-mass characteristics and temperatures of glass transition (T g) and melting (T m) have been examined by DSC, liquid chromatography, 1H NMR and IR spectroscopy, and chemical analysis of functional groups. Hydrogels and amphiphilic network polymers based on acrylamide monomers have been prepared and characterized.
 
The evolution of compositional heterogeneity and molecular-mass distribution in the course of micellar polymerization of weakly charged hydrophobically modified poly(acrylamides) has been studied. The relationship between the molecular characteristics, association behavior, and rheological properties of aqueous solutions and gels of these copolymers has been examined. The molecular-mass distribution broadens with conversion owing to accumulation of a low-molecular-mass fraction depleted of the hydrophobic monomer. A change in the molecular-mass distribution has a strong effect on the viscoelastic behavior of the polymers. The properties of the copolymers are dependent on the pH of the reaction mixture: the copolymers prepared in the alkaline medium show a more pronounced ability to experience hydrophobic aggregation than the copolymers prepared in the acidic medium. The aqueous solutions and the gels of these polymers are characterized by higher viscosities and dynamic moduli. The rheological characteristics of the hydrophobically modified poly(acrylamides) are improved with an increase in both their molecular mass and the length of hydrophobic sequences with a constant molecular mass.
 
Interfacial tension γ at the water/oil interface
High-molecular-mass hydrophobically modified poly(acrylamides) have been prepared via water-in-oil miniemulsion copolymerization of acrylamide and lauryl methacrylate initiated by 2,2′-azoisobutyronitrile. The incorporation of the hydrophobic comonomer into the polymer backbone is indirectly confirmed by the rheological and associative properties of polymer solutions. The copolymers prepared from the reaction mixtures containing less than 5 mol % lauryl methacry late demonstrate the associative behavior in aqueous solutions, as evidenced by fluorescence spectroscopy (a decrease in the polarity parameter of pyrene), static and dynamic light scattering (overestimated effective molecular masses and appearance of a peak due to aggregates), and rheological measurements (a rise of viscosity relative to that of the acrylamide homopolymer). A further increase in the content of lauryl methacrylate leads to formation of polymers possessing limited solubility in water. At the acrylamide-to-hydrophobic monomer equimolar ratio, homopolymers arise along with the insoluble copolymer.
 
A new water-soluble polyelectrolyte—the copolymer of sodium 2-acrylamido-2-methylpropanesulfonate and monoethanolamine vinyl ether—has been synthesized by free-radical copolymerization. The concentration behavior of the reduced viscosity of copolymer solutions that is typical for polyelectrolytes has been revealed. The reactivity ratios of the monomers have been measured. These values indicate a lower reactivity of monoethanolamine vinyl ether than that of sodium 2-acrylamido-2-methylpropanesulfonate. The complexation of this copolymer with poly(acrylic acid) and poly(N,N-dimethyl-N,N-diallylammonium chloride) has been studied. It has been found that the copolymer demonstrates the polyampholytic behavior and is able to form interpolymer complexes both with polycations and polyanions. It has been established that the polycomplex of the copolymer with polyacrylic acid has the unfolded structure due to the presence of sulfonate groups uninvolved in complexation, while the complex of the copolymer with poly(N,N-dimethyl-N,N-diallylammonium chloride) is compact owing to enhancement of hydrophobic interactions, and the sizes of its species are of the order of 80 nm.
 
Methods for the synthesis of emulsion-polymerized styrene-methyl methacrylate-methacrylic acid copolymers with different compositions and structures are proposed. Stable plastisols are obtained from these copolymers and phthalate plasticizers. Factors that affect the colloidal stability and rheological properties of the plastisols were studied. These are the polymer particle size, the type of surfactants used in emulsion copolymerization, the distribution of methacrylic acid units over the latex particle volume (uniform or gradient, with concentration rising from the particle center to periphery), the degree of carboxyl group neutralization with a base, and the nature of plasticizers. The plastisols obtained are characterized by a pseudoplastic flow. However, as the degree of carboxyl group neutralization in the copolymers is increased, the rheological properties of the plastisols approach those of Newtonian liquids.
 
The free-radical bulk homopolymerization of styrene and n-butyl acrylate at 80°C mediated by dibenzyl trithiocarbonate, poly(styryl) trithiocarbonate, or poly(n-butyl acrylate) trithiocarbonate as reversible addition-fragmentation chain-transfer agents has been studied. It has been shown that the use of low-and high-molecular-mass reversible addition-fragmentation chain-transfer agents makes it possible to efficiently control the molecular-mass characteristics of polymers. In the case of styrene, the rate of polymerization slightly depends on the concentration of the addition-fragmentation chain-transfer agent. In contrast, for the polymerization of n-butyl acrylate, the rate significantly decreases with the concentration of the chain-transfer agent. Formation of radical intermediates during the polymerization of styrene and n-butyl acrylate mediated by trithiocarbonates has been studied by ESR spectroscopy. It has been demonstrated that the polymeric chain-transfer agents are efficient for the synthesis of block copolymers with the controlled block length.
 
Monomer salts based on acrylic acids and guanidine—guanidine acrylate and methacrylate—have been synthesized, and the kinetic features of their free-radical polymerization in aqueous solutions have been studied. When polymerization is carried out in organic solvents (methanol, ethanol, or dioxane), the system is heterogeneous over the entire range of monomer concentrations. In aqueous solutions, the reaction systems are homogeneous only at small initial monomer concentrations (less than 1.30 and 0.40 mol/l for guanidine acrylate and methacrylate, respectively; the ammonium persulfate concentration is 5 × 10−3 mol/l; pH ∼ 6.5; 60°C). At higher concentrations, microheterogeneity appears from small conversions (∼1%). This phenomenon is associated with the coiling of growing polymer chains owing to associative interactions between guanidine groups occurring in the monomer solution and carboxyl groups of (meth)acrylate polymer units. In aqueous solutions over the entire range of monomer concentrations (0.2–2.5 mol/l), the kinetic orders are the same as in the case of corresponding acrylic acids. The effects of composition of reaction solutions on changes in the initial rate of polymerization and the conformational behavior of the systems under study have been ascertained.
 
The free-radical azeotropic bulk copolymerization of styrene and n-butyl acrylate at 90°C mediated by tert-butyl dithiobenzoate and copoly(strene—n-butyl acrylate) dithiobenzoate as reversible chain-transfer agents has been studied. It has been shown that low-and high-molecular mass chain-transfer agents allow one to efficiently control the molecular-mass characteristics of the copolymers. For all studied systems, the molecular mass linearly increases with conversion, and the copolymers are characterized by low polydispersity indexes. When polystyryl dithiobenzoate and poly(butyl acrylate) dithiobenzoate are used as polymer reversible chain-transfer agents in the azeotropic copolymerization of styrene and n-butyl acrylate, the diblock copolymers with the controlled block lengths are prepared. As evidenced by ESR studies, radical intermediates are formed in the course of the azeotropic copolymerization of styrene and n-butyl acrylate mediated by tert-butyl dithiobenzoate and the copolymer reversible chain-transfer agent; the kinetics of formation of these intermediates has been investigated. It has been demonstrated that the rate of the azeotropic copolymerization mediated by low-and high-molecular-mass reversible chain-transfer agents decreases with an increase in their concentration. The possible causes of this phenomenon are discussed.
 
Persistent length a and transverse size d for cylin- drical dendrimers in terms of the wormlike chain model Dendrimer-solvent a × 10 8 , cm d × 10 8 , cm 
Logarithmic dependences of (1, 2, 5, 6) [η] and (3, 4) diffusion coefficient D vs. the degree of polymerization Z for (1, 3, 5) P1 and (2, 4, 6) P2 in (1-4) bromoform and (5, 6) DCAA-LiCl. 
The conformational properties of poly(acrylate) with L-aspartic acid-based side dendrons of the first and second generations with hexyloxycarbonyl end groups have been studied by the methods of molecular hydrodynamics. Regularly branched dendrons are separated from the main chain by a benzamide fragment. The degree of polymerization of the main chain varies within 30-and 50-fold intervals for the dendrons of first and second generations, respectively. Mark-Kuhn-Houwink equations have been derived for poly(acrylate) in bromoform and dichloroacetic acid containing lithium chloride additives. The experimental results are discussed in terms of the models of the wormlike chain, weakly bent cylinder, and solid ellipsoid of revolution. On the basis of translational and rotational friction data, the persistent length of poly(acrylate) in bromoform and dichloroacetic acid containing small amounts of lithium chloride has been estimated.
 
The morphology of polymers prepared through the photoinduced polymerization of oligo(carbonate dimethacrylate) in the presence of different nonpolymerizable additives (methanol, dinonyl phthalate, hexane, toluene, benzene, and carbon tetrachloride) is studied via the method of atomic force microscopy. Depending on the nature and concentration of an additive, the photoinduced polymerization of the above composite systems is shown to be accompanied by microphase separation and formation of a porous polymeric material. In the case of methanol, homogeneous porous structures with characteristic pore sizes of several hundred nanometers are formed. In the case of dinonyl phthalate, the characteristic pore sizes lie below 100 nm. The synthesized porous polymers can sorb both polar and nonpolar solvents. The photoinduced polymerization of an oligomer in the medium of toluene, benzene, or carbon tetrachloride leads to the formation of polymer nanoparticles whose dimensions are controlled by the nature of a solvent.
 
Poly(ester urethane acrylates) with unsaturated bonds in stiff blocks have been synthesized from oligo(ester acrylates) containing functional groups. The structure and mechanical properties of the block copolymers thus prepared have been studied before and after UV cure. On the basis of the said poly(ester urethane acrylates), light-sensitive formulations for holographic recording have been designed. The formation of holographic gratings under illumination by an Ar laser light has been investigated. The formations under study offer promise as photostructuring media for holography.
 
In situ dielectric spectroscopy at frequencies ranging from 1 to 105 Hz was used to study chemical transformations during the heating of cobalt(II) and nickel(II) acrylates from −160 to +400°C. On the basis of analysis of the evolution of dielectric relaxation time spectra, processes that correspond to three macroscopic stages in different temperature intervals were distinguished: dehydration, solid-state thermal polymerization, and decarboxylation of metallopolymers. These processes lead to the formation of a polymer matrix that stabilizes nanosized metal or metal oxide phases. In the case of cobalt acrylate, the crosslinking step occurs in a temperature interval other than that of polymerization. It was found that electric conductivity varies over six orders of magnitude upon the formation of the nanosized metal phase.
 
Solubility of monomers 
Polymerization of monomers of series 1 
Solubility of polymers 
Polymerization of monomers with dendrons of first-third generations of series 2 
Two series of new acrylic polymers carrying L-aspartic acid-based dendrons in side chains with terminal hexyloxycarbonyl groups that are both directly and indirectly, via a rigid spacer, attached to polymer chains have been synthesized by the free-radical polymerization of monomers. The polymerization ability of the monomers has been studied. The properties of new polymers are compared with the properties of polymer analogs containing terminal methoxycarbonyl groups of dendrons. Upon incorporation of the rigid spacer, the shielding of reactive centers decreases and the polymerizability of the monomers increases. The replacement of terminal methyl groups in dendrons with hexyl groups in spacer-free polymers leads to a reduction in the degree of polymerization, while in the case of polymers containing spacers, high-molecular-mass products arise. This phenomenon is facilitated by the amphiphilic nature of the polymers and the additional enhancement in the rigidity of chains. A polymer carrying a third-generation dendron has been synthesized only for the latter series.
 
A series of macroporous poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAm-AA) hydrogels with different composition were synthesized by free-radical copolymerization in the presence of silica particles as a pore generating agent. The equilibrium swelling ratio, half swelling time and dynamic swelling kinetics of the copolymers previously soaked in different acidic buffer solutions were investigated at pH 7 at 25°C. Experimental results revealed that the swelling rate of the macroporous hydrogels was greatly increased compared to conventional hydrogels due to existence of the macroporous structures. It was found that the swelling history of previously putting in acidic solutions copolymers had strong influence on their dynamic swelling kinetics especially for the samples ranging in composition between 30 and 70 mol % of NIPAAm, whereas the swelling history had little influence on the equilibrium swelling ratio of copolymers. The swelling pattern exhibits sigmoid swelling curves. This is explained by an autocatalytic mechanism. The hydrogen bonding dissociation plays an important role in the dynamic swelling behavior.
 
The low-temperature copolymerization of N-vinylpyrrolidone with acrylic monomers (acrylic acid, acrylamide, and methyl acrylate) in vitrifying solutions in ethanol and DMF has been studied. It has been shown that the copolymerization proceeds after transition of preliminarily γ-irradiated at 77 K samples from the solid glassy state to a supercooled liquid. Experimental conditions that ensure formation of alternating and random block copolymers have been established. The composition of copolymers is determined by the relative mobility and initial ratio of comonomers in solution.
 
Molecular characteristics of initial copolymers 
Parameters of the Cross equation for the investigated styrene–acrylonitrile copolymer specimens 
Viscosity dependence on shear rate for linear (1)
and branched (2) copolymers at 220°C. The dark symbols correspond to shear viscosity and the light to complex dynamic viscosity.
Dependence of first normal stress difference on
shear rate for linear (1) and branched (2) styrene–acry lonitrile copolymers.
Extrudates of branched copolymer under shear stress 5.09 (1), 5.37 (2), 5.43 (3), 5.46 (4),5.51 (5) (a) and linear copolymer under 5.34 (1), 5.43 (2), 5.49 (3), 5.53 (4) (b).
A comprehensive investigation of rheological properties of linear and branched styrene-acrylonitrile copolymer specimens with similar molecular characteristics has been carried out. During the steady-state shear flow, the viscosity properties of both specimens are described by the Cross equation. In this case, the branched copolymer is characterized by a higher viscosity and shear thinning degree as well as by substantially lower shear rate values corresponding to transition to the non-Newtonian flow region. The elasticity of the branched copolymer melt (estimated from the value of the first normal stress difference) is considerably higher than that of the linear. This is reflected on the characteristics of occurrence of unstable flow at high shear rates. Rougher extrudate surface distortions are characteristic for the branched copolymer, and the shear rate corresponding to their occurrence is noticeably lower than for the linear copolymer. The dynamic characteristics of the copolymers being compared also attest to a greater elasticity of the branched specimen. An investigation of the viscoelastic properties in a wide temperature range allowed constructing a generalized frequency dependence of dynamic moduli encompassing various regions of the relaxation states of the copolymer specimens. Continuous relaxation spectra were calculated by means of the Mellin transform. It is shown that relaxation phenomena caused by segmental mobility doesn’t depend on the presence of branchings, whereas branching of the chain has a substantial effect on translation mobility of the chain as a whole. Branching leads to a noticeable increase of transient elongation viscosity but has almost no effect of strain hardening of the melt.
 
The relation of ozone resistance to the volume and structure of the interphase layer and the amounts of crosslinks in the interlayer was studied for covulcanizates of butadiene-acrylonitrile rubbers of various polarities with ethylene-propylene-diene (EPDM) elastomers that differed in the comonomer composition and stereoregularity of propylene units. It was shown that the ozone resistance is determined by the compatibility of the components, the interlayer volume and density, the amount of crosslinks in the interlayer, and the strength of the EPDM network.
 
The paramagnetic probe method with the use of free radicals of different dimensions (2,2,6,6-tet-ramethyl-1-piperidinyloxy and 4-benzoate-2,2,6,6-tetramethyl-1-piperidinyloxy) has been employed to study the effect of the isomeric composition of butadiene units in polybutadienes and butadiene-acrylonitrile copolymers on the number and dimensions of ordered structures. The nature of density fluctuations and defective regions, that is, the regions in which the radicals are sorbed, has been ascertained. It has been shown that the ordered regions are composed of stereoregular chain fragments, while defective regions are enriched with butadiene isomers different from those present in prevailing amounts.
 
We introduce here an ATP (adenosine triphosphate)-fueled nano-biomachine constructed from actin and myosin gels. Various types of chemically cross-linked actin gel, which are tens of times larger in size than native actin filaments (F-actin), were formed by complexing with cation-polymers and placed on a chemically cross-linked myosin gel. By adding dilute solution of ATP, they moved along the myosin gel with a velocity as high as that of native F-actin by coupling to ATP hydrolysis. Formation mechanism and structure of actin complexes as well as those of myosin gels were studied in detail and elucidated with the specific characteristics of the motility. These results demonstrate that one can construct nano-biomachines fueled by chemical energy of ATP with controlled motility.
 
The affinities of two anionic pyrenyl probes for pyridinium high-molecular-mass cations of different topologies—poly(N-ethyl-4-vinylpyridinium bromide) and a water-soluble poly(pyridylphenylene) dendrimer—are studied by the method of fluorescence quenching. The hydrophilic probe carrying three sulfonate groups in a molecule more efficiently interacts with a flexible highly charged linear polycation throughout the studied pH range. The binding of the dendrimer with a relatively hydrophobic probe containing a single carboxyl group is improved by acidification of solutions, and it becomes dominant in weakly acidic solutions. The interaction of DNA with the dendrimer containing the hydrophobic probe has no effect on the formation of the dendriplex and leads to displacement of only a small fraction of the bound probe into solution. Our model studies demonstrate that dual-action dendrimer carriers capable of simultaneous delivery of genetic material and hydrophobic drugs to target cells can be created.
 
Top-cited authors
Manoj Kumar Shukla
  • Kalaniketan Polytechnic College
Kamal Sharma
  • GLA University
Jong Pal Kim
Tatiana Bronich
  • University of Nebraska Medical Center
Natalia Nukolova
  • Serbsky National Research Centre for Social and Forensic Psychiatry