Polymer Science Series C

Published by MAIK Nauka/Interperiodica
Online ISSN: 1555-614X
Print ISSN: 1811-2382
Publications
The dependence of the ultimate shear strength of a lithium aluminosilicate ceramic-to-metal adhesive joint with the sealant Viksint U-2-28 on the thermal history of the samples was studied. A temperature threshold for a change in the strength of the adhesive joint was established. Possible mechanisms for the appearance of this threshold in terms of a change in the contribution of different components of the sealant to its adhesion properties, depending on the thermal aging regimes, are discussed.
 
Reported are the results of studying the influence of the composition of the complexes of transition metal salts with crown ethers on the kinetics of the curing of anaerobic adhesives developed in Kargin Research Institute of Polymer Chemistry and Technology. It is established that the use of copper salts makes it possible to substantially decrease the setting time on zinc-coated surfaces; however, in this case, the working life of adhesive decreases abruptly. It is shown that the activity of salts can be decreased by their complexation with various chelating agents. It is revealed that transition metal salts in the form of complexes with some crown ethers not only increase the rate of curing of anaerobic adhesives, but also considerably enhance the thermal stability of cured products that is explained by the ability of organic salts of metals to the inhibition of thermal-oxidative degradation of polymers.
 
The recent trends in the synthesis, characterization, and application of thiophene-containing polymers are surveyed. This review covers methods used for the synthesis of polythiophene and thiophene-based copolymers via oxidative dehydropolycondensation as well as electrochemical and metal-catalyzed polycondensations. The synthesis of polythiophenes carrying bridge groups annelated by aromatic rings is also discussed. The data on macromolecular transformations occurring during the synthesis of polythiophene, as well as on hyperbranched, macrocyclic, and organoelement thiophene-containing polymers, are summarized.
 
Reactivity ratios of copolymerization of N-vinylsuccinimine (M 1 ) with butyl acrylate (M 2 )* Solvent r 1 r 2 1/ r 1 1/ r 2 r 2 / r 1 r 1 · r 2 Calculation method
The testing results for copolymers of n-butyl acrylate with N-vinylsuccinimide used as medical adhesive materials are presented. These adhesives are designed to provide for the needed mechanical strength and also to be a conductor of physiologically active compounds. The copolymers under consideration are able to immobilize drugs containing amine groups. It is shown experimentally that vinylsuccinimide units in the copolymers with butyl acrylate can be easily and selectively transformed by alkali hydrolysis (without involving acrylate units) into units of N-vinylsuccinamic acid containing carboxyl groups, which makes it possible to immobilize physiologically active compounds on a polymer matrix such as this.
 
Methods of controlling the strength of adhesive joints via changes in the molecular mass of copolymers and incorporation of adhesion additives have been developed. The effect of the surface energy of substrates on the strength characteristics of the adhesive-bonded materials has been studied. It has been demonstrated that the adhesive strength increases with the time of contact.
 
The review covers the experimental and theoretical studies devoted to the anionic polymerization of esters and amides of acrylic and methacrylic acids containing groups with mobile hydrogen atoms. Within the framework of ideas concerning the kinetics and mechanism of the processes of interest and the structure of polymerization products, the practical applications of the polymers with diverse molecular architecture are discussed. A new family of water-soluble acrylamide monomers and the products of their free-radical polymerization have been synthesized and characterized.
 
Results of studying adhesive properties of epoxy resins modified with surfactants are reported. It is shown that surfactants with terminal fluorinated fragments have the highest activity. Ethers of a fluorine-containing telomeric alcohol and glycidol are employed as the surfactants. The surface tension is measured by the Rehbinder maximum bubble pressure method. The results of measuring surface tension and contact angles are presented. It is established that the use of organofluorine compounds with reactive groups makes it possible not only to decrease the surface tension, but also to “fix” molecules of these compounds at interfaces in the course of curing.
 
Potentialities of the modification of stress-strain properties of epoxy polymers of cold and hot curing are studied to produce thermally shrinkable couplings with “shape memory”. Various epoxy rubbers are used as modifiers and the curing was performed according to a stepwise regime with amine and anhydride curing agents. The result obtained shows that parameters of strength and deformation characteristics of polymer couplings can be varied within a wide range with the change in compositions of epoxy oligomers and curing agents. Regimes of coupling shrinkage and curing of adhesive layer are determined to ensure the reliability of coupling-adhesive joint of pipelines.
 
Examples of the use of thermal analysis instruments and techniques for the investigation and formulation of hot-melt adhesives are reported, and the feasibility of an immediate study of the effect of various components and process additives on the thermal, physical, and mechanical characteristics of adhesive joints is discussed.
 
The results of testing of carbon-and glass-reinforced plastics for dust and droplet-impact erosion are reported. The experiments were performed on an U17-P aerodynamic facility and a CS-871 centrifugal self-balancing apparatus.
 
A procedure is proposed for determining the impact resistance of composite materials based on glass-and carbon-reinforced plastics and adhesive materials used as binders. Characteristics of the impact resistance are determined using a pendulum tester upon impact by a spherical steel indenter. It is shown that the most informative characteristic for estimating the impact resistance of composites is the work absorbed by the material upon impact. For comparative estimation of the impact resistance of different materials, whose specimens may have different thicknesses, it is convenient to use relative rather than absolute values of impact resistance. The relative value is calculated by dividing the maximum contact force by the specimen thickness. Glass-fiber laminates based on adhesive prepregs 1.9 and 2.1 mm thick and three-layer honeycomb panels were tested. Materials based on KMKS 2.120.T10 adhesive prepreg possess the best impact resistance.
 
Procedures for determination of basic quality characteristics of epoxide-bisphenol A resins and amine hardeners: the epoxide equivalent and the amine value, respectively; the viscosity; and the pot life are reported. A rapid method for the assessment of the gelation time of a mixture of an epoxy resin with a hardener is described.
 
The commercial production of epoxy resin ED-20 is discussed as this resin is the most important component in the formulations of adhesives and sealants in the Russian Federation. Classification of amine hardeners is presented, and basic trade marks of ethylene amines, modified amines, oligoaminoamide and imidazoline hardeners are listed, and their major characteristics are described.
 
The complex effect of shock-wave and thermal treatments on the adhesion of thermoplastic polymer coatings to aluminum and its alloys is studied. Being subjected to explosive loading, polymers are activated via the rupture of chemical bonds and the formation of free radicals and new functional groups. Subsequent thermal treatment leads to the activation of oxygen, resulting in the formation of chemical bonds between a polymer and a metal surface. The mechanism of thermal oxidation is considered. The optimum temperature-time regimes of the shock-wave treatment are determined, which permits obtaining polymer coatings on aluminum alloys in joints whose strength is 2–3 times higher than for joints obtained with unmodified materials. Powdered fluoroplastic and ultrahigh-molecular-mass polyethylene are used as adhesive materials.
 
Results of a study are reported on the utilization of ground vulcanizate, which is a waste product of rubber prcoessing plants. Loaded stocks of various commercial rubbers act as objects for the study. Talc, kaolin, silicon dioxide, and furnace carbon black are used as fillers. According to the results of a study on the effect of the amount of rubber crumb, an increase in the content of unmodified crumb leads to a decrease in tear resistance that is associated with poor wettability. To increase wettability, we use organosilicon couplings. It is shown that the addition of vulcanizate to rubber stocks, together with highly dispersed fillers treated with organosilicon couplings, leads to a significant increase in tear resistance and makes it possible to significantly reduce the cost of production and utilization.
 
The influence of polysulfide and carboxylated butadiene rubbers on the mechanical characteristics of epoxy-rubber adhesives is studied. The optimal concentration of rubbers is determined and the technology of compounding carboxylated rubbers and an epoxy oligomer is described. The character of changes in stress-strain characteristics for bulk specimens and films prepared on the basis of modified and unmodified epoxy oligomers is determined. The procedure for measurement of the wear resistance index is discussed and the advantages of carboxylated rubbers compared to Thiokol are demonstrated. The properties of a new cold-setting epoxy-rubber adhesive with an improved shelf life and good stress-strain and dielectric characteristics are presented.
 
Filled cyanoacrylate adhesive compositions possessing electro-and heat-conducting properties have been developed. These compositions are recommended for panel wiring of electro-and radioelements and hermetic sealing of aluminum casting.
 
The results of testing of epoxy adhesives joints for long-term strength, chatter stability, and water and heat resistance are reported.
 
Concentration dependences of the strength of filled epoxy resin-steel wire (diameter 150 μm) adhesive joints are studied. Nanostructural powders of aluminum oxide with cylindrical particles (diameter 4–6 μm and length 30–40 μm) are used as fillers. The structure of cured compositions is studied by X-ray diffraction techniques and it is established that nanostructural Al2O3 fibers are porous. The effect of the scale factor is studied. It is shown that the breaking force increases nonlinearly and the strength of the adhesive joint decreases with an increase in the bonding area. It is established that the dependences of adhesive strength on concentration are described by curves with maxima. This makes it possible to recommend highly dispersed fillers as a method for the control of interfacial strength.
 
The feasibility of controlled changes in the characteristics of epoxy adhesives via modification with inert and reactive plasticizing agents, oligomers, and hardeners is considered with account for their chemical structure and hardening schedule.
 
Advantages and disadvantages of the anodic oxidation method, which is widely used for the preparation of metal and alloy surfaces for adhesive bonding, are considered. A new technology is proposed for the preparation of metal surfaces using a combined electrolyte and an organic corrosion inhibitor. The advanced technology permits increasing the moisture resistance of adhesive joints by three to five times. The results of comparative tests of corrosion activity of a large body of adhesives based on modified epoxy and phenol-formaldehyde oligomers, as well as rubbers, are described. Phenol.-rubber adhesives are shown to possess protective properties and demonstrate corrosion activity, thus increasing the durability of adhesive joints.
 
Characteristics of epoxy adhesives for special purposes are described. These adhesives are used for joining together various substrates based on polyamides, ferrite, quartz, ceramics, and resins based on fluoroorganic rubbers.
 
The effect the curing conditions on the properties of adhesive joints formed using cyanoacrylate-based adhesives is investigated. The effect the curing conditions on the properties of adhesive joints formed using cyanoacrylate-based adhesives is investigated. The temperature dependences of relative rigidity and mechanical loss tangent are studied by torque analysis for poly(ethyl-, The temperature dependences of relative rigidity and mechanical loss tangent are studied by torque analysis for poly(ethyl-, allyl-, allyloxyethyl-, allyloxyisopropyl-, propargyloxyethyl-, and propargyl-) cyanoacrylates after their thermal treatment allyl-, allyloxyethyl-, allyloxyisopropyl-, propargyloxyethyl-, and propargyl-) cyanoacrylates after their thermal treatment in the temperature range of 20–250°C. The glass transition parameters of polycyanoacrylates and the dependence of the curing in the temperature range of 20–250°C. The glass transition parameters of polycyanoacrylates and the dependence of the curing intensity on the structure of initial monomers and polymers are determined. It is established that the elastic modulus decreases intensity on the structure of initial monomers and polymers are determined. It is established that the elastic modulus decreases with the lengthening of alkyl radicals in side chains. A list is experimentally determined of monomers used to obtain adhesive with the lengthening of alkyl radicals in side chains. A list is experimentally determined of monomers used to obtain adhesive compositions with stable physicomechanical properties and heat resistances of up to 250°C. compositions with stable physicomechanical properties and heat resistances of up to 250°C.
 
The results are reported of studies of adhesives based on polyurethanes containing carborane groups. It is established by TGA methods that for polyurethane-carborane systems, total mass losses upon heating to 600°C are equal to 20%, whereas for adhesives free of carborane groups, such losses are equal to 80%. It is revealed that the properties of the adhesives studied are substantially affected by carborane isomeric structure. Compositions containing polyestercarboranes with m-carborane provide higher stability of adhesive joints to elevated temperatures. Results of the study of the kinetics of gas evolution are reported and the scheme of the two-stage mechanism of thermal degradation is proposed. Results of IR spectroscopy analysis show that upon the curing of carborane-containing polyurethane composition, isocyanate groups of polyisocyanate first interact with hydroxyl groups of polyestercarborane, which results in the formation of macrodiisocyanates. Subsequent heating to 350°C leads to further curing of compositions that involves carborane, ester, and polyurethane groups.
 
The properties of a family of urethane adhesives and sealants suitable for a wide range of repair works under field conditions have been studied. The distinctive feature of these materials is a good combination of strength, deformation, electrical, and thermal characteristics.
 
Requirements for adhesives used in the surface-mount technique are presented. Properties of a heat-setting epoxy adhesive TPK-4 designed at the Semenov Institute of Chemical Physics of the Russian Academy of Sciences together with the OOO NPF Tekhpolikom are described.
 
Factors governing thermal aggregation and thermal denaturation of a model homotetrametric enzyme, glyceraldehyde-3-phosphate dehydrogenase, electrostatically bound to a polyelectrolyte are revealed. Polyanions with sulfate or sulfonate groups in chains are the most efficient suppressors of aggregation. However, their presence promotes thermal denaturation. Short chains of relatively hydrophobic polyanions exert a strong denaturing effect that changes the secondary, tertiary, and quaternary structures of a protein. Basic guidelines for the selection of a polyelectrolyte are outlined. According to the proposed guidelines, hydrophilic high-molecular-mass macromolecules able to form stable soluble polyelectrolyte complexes with the enzyme are the most efficient at preventing thermal aggregation without substantial loss in catalytic activity.
 
Published data concerning the problem of the physical aging of glassy polymers are surveyed. Basic attention is given to an analysis of structural rearrangements that accompany the physical aging of glassy polymers. The processes of aging (spontaneous change in the properties of polymer glasses during the storage at a temperature below the glass transition temperature) can be classified into the two following categories: first, the aging of undeformed polymer glasses and, second, the mechanical stress-induced aging of a polymer. It is shown that in the former case, the processes occur throughout the entire body of the polymer and, in the latter case, the aging processes is concentrated in microscopic zones (shear bands) that emerge during polymer deformation. The current concepts of the aging of polymer glasses are discussed.
 
Metallopolymers based on unsaturated alkoxides of refractory metals (Ti(IV), V(V), Ta(V), Nb(V)) are synthesized and characterized; their thermal behavior is studied via TGA, TMA, and DSC. It is shown that nanocomposite materials can be synthesized through the polymerization of metal-containing monomers and subsequent controlled thermolysis of the products.
 
To reveal the features of the structure of UHMWPE that depend on the catalytic system used for synthesis, a comparative study of the sets of laboratory and commercial powders of UHMWPE synthesized on different catalysts in the slurry process under different conditions is conducted. This study includes the use of various modern physical methods, such as transmission and scanning electron microscopy, X-ray analysis, Raman scattering spectroscopy, differential scanning calorimetry, nuclear magnetic resonance, and thermoluminescence. All nascent particles are shown to have a complex hierarchical structure. In all reactor powders, the elementary structural unit is crystalline lamellas, whose dimensions and mutual orientation are dependent on the type of catalytic system. In the synthesis on the supported catalysts, the character of the formed structure depends on the characteristics of the substrate. During the breakdown of the substrate in the course of the synthesis, fibrils form. The colloidal dimensions of the catalyst particles are responsible for a more uniform lamellar structure of the reactor powders. The conformational composition of the segments of molecules in the interlamellar regions of the reactor powders is characterized.
 
Poly(ester dimethacrylate) has been synthesized by condensation of the ɛ-caprolactone-based macromonomer and 2-hydroxyethyl methacrylate with dicyclohexylmethane diisocyanate. Network copolymers of different compositions capable of swelling in water, THF, and toluene are obtained by the free-radical copolymerization of poly(ester dimethacrylate) with N-isopropylacrylamide or 2-hydroxyethyl methacrylate. The rate constants and equilibrium swelling indices of network copolymers in these solvents are measured. The amphiphilic properties of the network copolymers can vary in a wide range depending on the composition of copolymers and the nature of a hydrophilic monomer. The copolymers of poly(ester dimethacrylate) with N-isopropylacrylamide are characterized by pronounced thermal sensitivity.
 
The influence of anionic amphiphilic compounds that have different geometric shapes and become incorporated into bilayers on the polycation-mixed liposome interaction and the structure and properties of the resulting complexes is analyzed. Phosphatidylserine, cardiolipin, and sodium dodecyl phosphate are used as anionic lipids, and poly(N-ethyl-4-vinylpyridinium bromide) and polylysine are used as polycations. Polycation adsorption on the surfaces of all examined types of liposomes is accompanied by the neutralization of their charge, an increase in the size of particles of the systems, and quenching of fluorescence labels. Liposomes whose membranes contain incorporated cylindrical phosphatidylserine molecules retain their integrity during contact with polycations. The resulting complexes quantitatively dissociate into initial components during an increase in the salt concentration in the surrounding solution. In the case of liposomes with asymmetric anionic lipids, that is, cardiolipin and sodium dodecyl phosphate, the conditions of retaining the membrane integrity and reversible complexation are fulfilled only at relatively low molar fractions of both lipids. The obtained data witness the decisive effect of the geometry of anionic lipid molecules on the stability of complexes formed from mixed liposomes and polycations.
 
Recent achievements in the synthesis of polyethers based on bisphenols containing various heterocyclic (azole, benzazole, azine, benzazine, imide) and high-condensed groups are surveyed. The best results are obtained when polyethers are prepared via aromatic nucleophilic substitution reactions involving activated carbocyclic difluoroaromatic compounds as comonomers of heterocyclic bisphenols. Special attention is given to new polymer-forming coupling reactions giving rise to N-C bonds.
 
The molecular characteristics of cylindrical first-third generation dendrimers carrying dendrons based on L-aspartic acid are compared. It is shown that both the generation number of side dendrons and their structure determine the conformational, hydrodynamic, optical, and dipole characteristics of dendrite macromolecules. It is found that the studied class of cylindrical dendrimers is distinguished by a marked amount of intramolecular hydrogen bonds between side dendrite substituents. These bonds ensure the unusual combination of high kinetic rigidity and a compact conformation (low equilibrium rigidity) of macromolecules. The rupture of hydrogen bonds leads to an enlargement of molecular coils (an increase in equilibrium rigidity) that is accompanied by a sharp drop in kinetic rigidity.
 
The major achievements in the field of controlled atom-transfer radical polymerization, the most promising method of living radical polymerization, are analyzed. The relationship between the structure of a regulating agent and its activity under the conditions of controlled radical polymerization, including the efficiency of metal-complex catalysts for the targeted synthesis of macromolecules with predetermined molecular-mass characteristics, chain structure, and properties, is examined. Main trends in the development of this area of polymer chemistry are highlighted.
 
A monomer of the A-B type, 3,4-diamino-4'-carboxydiphenyloxide, has been synthesized via a series of consecutive transformations of 5-chloro-2-nitroaniline. The homopolycondensation of the monomer in Eaton's reagent at 140A degrees C yields poly[2-(4'-oxyphenylene)-5-benzimidazole] soluble in organic solvents. A membrane containing 51% H(3)PO(4) (2.9 acid molecules pert monomer unit) and possessing a proton conductivity of 0.025 S/cm at 160A degrees C is produced by doping a polymer film with 60% H(3)PO(4).
 
Main directions of studies initiated by Al.An. Berlin that were further successfully elaborated in the synthesis of polymerazible oligomers are reviewed. In the field of oligoesteracrylate synthesis, a new class of materials, anaerobic adhesives, and acrylic oligomers or their mixtures with initiating systems providing for the fast polymerization in the absence of oxygen within a wide range of curing conditions was developed. Methods of the synthesis of epoxypropiolates from various bisphenol A-based epoxy oligomers in the presence of excess propiolic acid were developed. The distinguishable feature of polymers synthesized is their high adhesion to glass. The mechanism of the formation of oligocarbonate methacrylates was verified that open wide vistas for the control of the properties of some types of oligomers. Oligocarbonate methacrylates were modified to improve their thermal and thermal-oxidative stability. A new method of oligourethane methacrylate synthesis without using isocyanates is considered. Prospects for the application of oligoimides to prepare compositions with liquid reactive oligomers are discussed that allows, using the method of “liquid molding,” for producing thermostable items.
 
The results of investigating highly thermostable polymer matrices with softening temperatures of 400–450°C are reported. Binders based on a tetranitrile of an aromatic tetracarboxylic acid and bis(o-cyanoamine) are used as polymer matrices. Traditional antioxidants, such as aromatic amines, phenols, and alkyl aryl phosphites, cannot be applied as thermostabilizers. Detailed tests of an efficient stabilizer carborane-containing dinitrile were also unsuccessful because the initial period of retardation in the thermal-oxidative degradation is followed by irreversible changes in the polymer at 350–400°C. Only a new thermostabilizing system based on carborane-containing aromatic compounds with a set of conjugated bonds demonstrates a positive effect. It is established that the developed thermostabilizing system retards the thermal-oxidative degradation and makes it possible to obtain the polymer matrix with a thermal stability of 350–400°C.
 
Properties of mastics on the basis of polychloroprene and ethylene-propylene diene rubber SKEPT-40 designed for the sealing of edges of outer wall panels are considered. Quinol ether was used as a curing agent. The stability of vulcanizates in an ozone-air atmosphere is studied by the stress relaxation method, and it is established that the rate of stress relaxation decreases at a SKEPT content above 15%. Molecular dynamics in vulcanizates is investigated by electron paramagnetic resonance. It is revealed that the use of polychloroprene and an ethylene-propylene diene rubber blend in a 70: 30 ratio makes it possible to prepare sealing coatings with high service characteristics.
 
Experimental results obtained during the past 50 years in studying the compatibility between the components in rubber-containing blends and solutions under static conditions and in the presence of mechanical field have been surveyed and analyzed. Phase diagrams of polymer-polymer and polymer-polymer-solvent systems are presented. Causes of phase separation of the systems are considered. The corresponding phase diagrams are analyzed with respect to the chemical macromolecular structure of polymer components. Changes in phase separation temperatures of the polymer systems under shear deformation are discussed; inversion in the effect of the mechanical field on the solubility of the constituent components is described; at low strain rates, solubility appears to be improved, whereas at high strain rates, solubility decreases.
 
Polycaproamide composites are synthesized by the anionic activated bulk polymerization of ɛ-caprolactam in the presence of 0.1–5.0 wt % of multiwalled carbon nanotubes and using low-molecularmass monofunctional (N-acetyl-ɛ-caprolactam) and macromolecular polyfunctional (aromatic polyimides) activating agents. The effect of nanotubes on the polymerization of ɛ-caprolactam is studied, and this effect is shown to become more pronounced as the concentration of nanotubes is increased. The effect of nanotubes on the microstructure, phase composition, water sorption, thermophysical, mechanical, and friction characteristics of poly(caproamide) is analyzed.
 
The synthesis and properties of carbochain polymers with side azole groups containing three and four heteroatoms are considered. The data on the synthesis of vinyl derivatives of oxadi-, tri-, and tetrazoles and their polymerizability are systemized and generalized. The potential of polymer-analogous transformations for preparation and modification of polyvinylazoles are demonstrated. The structure-property relationships for the mentioned polymers are analyzed.
 
This review summarizes the data on catalytic addition polymerization of norbornene and its derivatives catalyzed by various transition-metal complexes. Studies on the copolymerization of norbornene with α-olefins are considered. The survey mostly covers papers published in 2000–2006.
 
The complexation of DNA with a dendrimer with the successive addition of the dendrimer solution to the solution of DNA leads to the appearance and accumulation of compact particles with a diameter of D h = 100 ± 10 nm that coexist with particles whose dimensions coincide with those of free DNA molecules (D h = 450 ± 50 nm). The fraction of large particles decreases regularly; moreover, when the equimolar ratio of charged groups of interacting components is achieved, these particles disappear. The coexistence of practically free DNA molecules and a compact soluble negatively charged complex is confirmed by a sedimentation assay. Further addition of the dendrimer up to a certain ratio of charged groups of the components, much higher than unity, brings about phase separation, while at a large excess of charge groups of the dendrimer (above fivefold), the system turns out to be fully single-phase and composed of compact (110 ± 10 nm) cationic soluble complexes. Owing to the positive charge and small size of complex particles no greater than a critical value of 150 nm, the particles possess an important ability to interact with a positively charged cell membrane and to enter a living cell via endocytosis.
 
Conditions of synthesis and molecularmass characteristics of polymeric RAFT agents 
Substitution constants k subs for the reaction of tertbutyl radical with polymeric RAFT agents 
The spin-trapping technique is used for the first time to study the kinetics and mechanism of addition and fragmentation elementary events in reversible addition-fragmentation chain-transfer pseudoliving radical polymerization. As shown by the example of the spin-trap-reversible addition-fragmentation chaintransfer agent model system, the constants of addition (substitution) of the model tert-butyl radical to polymeric reversible addition-fragmentation chain-transfer agents (poly(styrene dithiobenzoate), poly(n-butyl acrylate) dithiobenzoate, etc.) are one to two orders of magnitude higher than the constants of addition reactions involving low-molecular-mass reversible addition-fragmentation chain-transfer agents (tert-butyl dithiobenzoate, benzyl dithiobenzoate, di-tert-butyl trithiocarbonate, and dibenzyl trithiocarbonate). This circumstance makes it possible to significantly widen the synthetic possibilities of reversible addition-fragmentation chain-transfer polymerization. Rate constants of the fragmentation reaction for a number of intermediates are estimated, and the relationship between their structure and stability is ascertained. For the model reaction of the interaction (addition and fragmentation) of the tert-butyl radical with low-molecular-mass reversible addition-fragmentation chain-transfer agents, equilibrium constants are calculated via the methods of computational chemistry.
 
The synthesis and structure of organo-inorganic nanocomposites prepared by intercalation of monomers or polymers into the interlayer galleries of layered matrices are analyzed. General features and the mechanism of the intercalation process, as well as materials used for this purpose, mostly often naturally occurring materials (clays, silicates, layered phosphates, chalcogenides, and other moieties hosts), are discussed. Mechanisms governing the intercalation of monomers or polymer repeating units into the interlayer galleries as guests are compared. One of the most widespread and commercially important intracrystalline chemical reactions is the incorporation of monomer molecules into pores or layered lattices of the host substances with subsequent post-intercalation transformations into polymer, oligomer, or hybrid-sandwich products. This strategy is used for the design of organo-inorganic self-assembling nanocomposites as multilayers (P/M)n, where M and P are nanosized oppositely charged layers of an inorganic component and a polymer. Particular emphasis is placed on nanocomposites based on polyconjugated conducting polymers (polyaniline, polypyrrole, etc.) and various mineral matrices, as well as on semiconductor polymer-metal chalcogenide inclusion nanocomposites. Basic application areas of hybrid nanomaterials are considered.
 
The main features of the manifestation of polymer characteristics of macromolecular nanoobjects are summarized and analyzed in comparison with classical linear systems. This study is primarily focused on dendrimers that exhibit qualitative changes in their characteristics after passing from lower to higher generations within the same homologous series. The above changes are shown to be typical for other representatives of a similar class of polymers.
 
The equilibrium Kerr effect and its dynamics are investigated in isotropic melts of the comb-shaped LC polymer poly(4-[(4′-cyano-1,1′-biphenyl-4-yl)oxy]butyl-2-acrylate) and its copolymers with acrylic acid or methyl methacrylate and isotropic melts of the LC ionomer containing rubidium ions in a wide temperature range. A sharp change in the temperature dependence of relaxation times for the induced macroscopic orientational order is found for the LC copolymers and the LC ionomer in the temperature range 10–15 K higher than the temperature of the nematic-isotropic phase transition. In contrast, the phenomena caused by the small-scale dynamics, such as electric conductivity and dipole relaxation, are approximated by the conventional Arrhenius type dependence, and the equilibrium electrooptical properties of the copolymers are well characterized via the Landau-De Gennes model. The nonclassical behavior of macroscopic relaxation times may be associated with temperature variations in the contribution of main polymer chains to the orientation macroscopic dynamics of the melt, in which the decisive role is played by side mesogenic groups.
 
Optical density at λ= 310 nm vs. concentration of LaCl 3 for a DNA solution in 0.005 M NaCl at [DNA] = (1) 0.001, (2) 0.002, (3) 0.003, (4) 0.004, and (5) 0.005%.
Phase diagram for DNA solutions in 0.005 M NaCl containing lanthanum ions.
AFM images of DNA cast on the surface of mica from solutions containing 0.0005 mol/l of (a–d) magnesium or (d–g) manganese. The concentrations of ethanol are (a) 10, (b, f) 20, (c) 55, (d) 75, (e) 0, and (g) 35 vol %.  
Changes in the tertiary structure of a high-molecular-mass DNA in solution that result from the addition of trivalent lanthanum ions, including intramolecular structuring of the macromolecule, are studied by atomic-force microscopy. The effect of bivalent magnesium and manganese ions on the structure of DNA in an aqueous-alcohol solution is analyzed. The data are compared with the results of viscometry, dynamic light scattering, flow birefringence, circular dichroism, and UV spectrophotometry.
 
Items are classified according to the requirements on their sealing, and general demands on the degree of sealing of structures used in various branches of industry are described. The coefficients of media diffusion obeying the Fick and Henry laws through many polymeric materials are given. Factors affecting the diffusion coefficients are considered. The technology of contour sealing along the outer surface of technological shells and internal surface of final items is described. Advantages and disadvantages of each sealing method considered are shown. The technological specific features of local sealing of dismountable joints are described. The technology of sealing of flanged and nipple joints is discussed.
 
Top-cited authors
Anatoly Zinchenko
  • Nagoya University
Vitaly Vorobiov
  • Institute of Macromolecular Compounds Russian Academy of Sciences
Michael A. Smirnov
  • Institute of Macromolecular Compounds Russian Academy of Sciences
Alexander Yakimansky
  • Russian Academy of Sciences
Maria P. Sokolova
  • Institute of Macromolecular Compounds of the Russian Academy of Sciences, St.Petersburg, Russia