Showing papers in "Polymer Science U.s.s.r. in 1982"
TL;DR: In this paper, a generalized equation derived for the spinodal allows for the formation of periodic heterogeneity (i.e. domain structure) in the volume-homogeneous state of heteropolymers.
Abstract: The part played by composition fluctuations in breaking up the volume-homogeneous state of heteropolymers has been analysed in some detail. A generalized equation derived for the spinodal allows for this breakup occurring by way of the formation of periodic heterogeneity (i.e. domain structure). The character of the density-density correlation function in the homogeneous state in the vicinity of the spinodal has been determined and relations between its parameters and the period of the domain structure are considered. The first stage of growth of the domain structure, where the linear theory of slightly nonequilibrium systems is applicable, is discussed.
46 citations
TL;DR: In this paper, the cyclization of poly(4,4′-oxydiphenylene) pyromellitamido acid in the solid phase under the effect of acetic anhydride in the presence of pyridine has been investigated.
Abstract: The cyclization of poly(4,4′-oxydiphenylene) pyromellitamido acid in the solid phase under the effect of acetic anhydride in the presence of pyridine has been investigated. From the IR spectra of the products of cyclization, the changes with time in the optical density of the absorption bands characteristic of o-carboxyamide groups and of imide and iso-imide rings have been followed. The process of chemical imidization is described by a scheme that includes the closing of o-carboxyamide groups to form imide and iso-imide rings as two parallel first order reactions as well as the isomerization of iso-imide rings to form imide rings as a reversible first order reaction. A probable mechanism for the chemical imidization of the polyamic acid is proposed on the basis of the kinetic data.
33 citations
TL;DR: In this paper, the spinodal temperature of the three-dimensional homogeneous state of a copolymer was investigated and the dependence of these values on chemical structure with random composition of the copolymers was analyzed by calculation for a number of mono-dispersed melts.
Abstract: A study was made of two-component (both block and graft) copolymer melts. Asymptotic (low content of one of the components) expressions were derived for the spinodal temperature of the three-dimensional-homogeneous state of a copolymer, which show a slight deviation from the temperature of spinodal of a duly selected system of “ruptured units”. The period of domain structure formed is approximately equal to the geometric mean of Gaussian dimensions of short A units and long B units. The dependence of these values on chemical structure with random composition of the copolymer was analysed by calculation for a number of mono-dispersed melts.
27 citations
TL;DR: In this paper, the morphology of polypropylene granules forming directly in the polymerization process was studied by scanning electron microscopy, and by adsorption and mercury-porometric methods.
Abstract: The morphology of polypropylene granules forming directly in the polymerization process was studied by scanning electron microscopy, and by adsorption and mercury-porometric methods. Separate structural elements were isolated which consisted of the polypropylene granules and a link was established between these and the structural elements of the catylast particles. A mechanism of formation of such granules has been established on the basis of the findings; it is suggested that the granules form on the internal surfaces of the porous catalyst.
25 citations
TL;DR: The results of the investigations of polymer crystallosolvates are generalized in this article, where the paths of formation of the crystallosols, characteristic features of their structure and the main most typical properties are examined.
Abstract: The results of the investigations of polymer crystallosolvates are generalized. The paths of formation of the crystallosolvates, the characteristic features of their structure and the main most typical properties are examined. Special attention is paid to phase equilibrium in systems with formation of crystallosolvates and certain practical aspects of the processing of such polymer systems.
24 citations
TL;DR: In this article, the authors used adiabatic and isothermal calorimetry for the first time to study thermodynamic properties of dl-lactide, poly lactide and thermodynamic parameters of polymerization.
Abstract: Adiabatic and isothermal calorimetry were used for the first time to study thermodynamic properties of dl-lactide, polylactide and thermodynamic parameters of polymerization of dl-lactide. Specific heat C°p was measured with an accuracy of ∼0·2% in the range of 8–330°K and 0·7% in the range of 330–430°K. Functions of H°(T)−H°(0), S°(T), G°(T)−H°(0) of the monomer and polymer were calculated for the range of 0–430°K. Zero entropy S°c(0) of the polymer was determined in the glassy state. Combustion enthalpy values of the monomer and polymer were measured and standard parameters of the formation of these substances ΔH°f, ΔS°f and ΔG°f, calculated. From results obtained thermodynamic parameters of polymerization of lactide ΔH°p, ΔS°p and ΔG°p were alculated for the range of 0–430°K; the upper maximum temperature of polymerization T°u was established.
16 citations
TL;DR: In this article, it was shown that a diagram of state with four regions (four-regional diagram) does not hold for a solution of semi-rigid macromolecules with extended segments.
Abstract: It is shown that a diagram of state with four regions (four-regional diagram) does not hold for a solution of semi-rigid macromolecules with extended segments. The proposed five-regional diagram contains a mean field region with paired collisions of segments. The width of this region increases with increasing rigidity of the chain. In the mean field region (with double and triple collisions of units) the density of eigen-units inside sections (blobs) determined by the correlation radius is smaller than the mean density of units in solution. The number of eigen-units in a “blob” and the number of contacts per “blob” are determined by the average concentration of the solution and do not depend on the rigidity of the chain.
15 citations
TL;DR: In this article, a study was made of the stretching of high density polyethylene and isotactic polypropylene in liquid media which swell the materials, and the deformation of crystalline polyolefines was largely determined by the propagation of specific microcracks.
Abstract: A study has been made of the stretching of films of high density polyethylene and isotactic polypropylene in liquid media which swell the materials. Under these conditions the deformation of crystalline polyolefines is largely determined by the propagation of specific microcracks. The presence of plasticizing media results in a significant reduction in the forced elastic limit and in the stress of stationary development of deformation. Changes in the mechanical properties of the PE and PP under these conitions are determined both by the plasticizing action of the liquid media and by their ability to reduce the surface energies of polymers.
15 citations
TL;DR: In this paper, the authors show that the difference in the structure of the two PE types mainly affects the small-scale relaxational transition in the crystalline phase, and the three high temperature transitions are similar to λ-processes in elastomers.
Abstract: The methods of relaxational spectrometry (from the spectra of internal friction) in low density PE have revealed eight physical relaxational processes (in the temperature interval from — 160 to T m = 109°C). Of them the two low temperature transitions correspond to the small scale movements of the CH 2 groups in PE chains in the amorphous and crystalline phases. The three following transitions are linked with the mobility of the segments in different structural regions (amorphous phase, interphasic layer and in the amorphous portions of the crystalline rays of the spherulites). The three high temperature transitions are similar to λ-processes in elastomers. From comparison with the data on relaxational spectrometry of high density PE it follows that the difference in the structure of the two PE types mainly affects the small-scale relaxational transition in the crystalline phase.
13 citations
TL;DR: In this paper, substitution reactions on a macromolecular system containing two different types of poly-anions, namely sodium polymethacrylate (A), sodium polyethylene sulphonate (B), and the poly-cations of poly 4-vinyl-N-ethylpyridinium bromide (C), were investigated.
Abstract: Substitution reactions were investigated on a macromolecular system containing two different types of poly-anions, namely sodium polymethacrylate (A), sodium polyethylene sulphonate (B), and the poly-cations of poly-4-vinyl-N-ethylpyridinium bromide (C). The reaction was carried out by adding to the water-soluble non-stoichiometric poly-electrolytic complex (PEC) portions of the competing polymer: PEC(AC) +B⇆PEC(BC)+A (1). Reaction (1) can have two mechanisms depending on the reaction conditions; firstly dissociation of PEC(AC) will cause the C-parts to enter the solution where their bonding of the B macromolecules will yield PEC(BC), and secondly by an electrostatic reaction of the B-parts with the ionic groups of C present in the defects (loops) of PEC(AC) to form mixed ternary PEC which are then transformed to PEC(BC) due to phase-separation of the solutions. Variation of the reaction (1) conditions (addition of a low mol.wt. electrolyte, a change of the length of the polymeric reagents, etc.) can result in an effective control of the substitution route in one or the other direction. The general validity of the process types described is shown.
12 citations
TL;DR: In this article, the features of the glass transition of amorphous layers of oriented, flexible polymers were studied and the connection of glass formation with the functional distribution of length of cross chains was discussed.
Abstract: The features of the glass transition of amorphous layers of oriented, flexible polymers were studied. The micro-regions, whose chains do not participate in meanscale segmental (microbrownian) motion were considered to be glassy, Chain rigidity was observed by NMR. It is concluded that the wide distribution of glass transition points is due to the entropy factor, related to the variety of lengths of cross (tie) chains. The connection of glass formation with the functional distribution of length of cross chains is discussed. Thermal glass transition is compared with the mechanical one, caused by stretching forces.
TL;DR: In this article, the theory of time dependence of the strength of polymer glasses in surface active media has been examined and expressions for the rate of crack growth and also equations of durability in these media, generalizing the analogous results in a vacuum, obtained earlier.
Abstract: The theory of time dependence of the strength of polymer glasses in surface active media has been examined. Expressions are proposed for the rate of crack growth and also equations of durability in these media, generalizing the analogous results in a vacuum, obtained earlier. Relations for safe stress, the level of reduction of the potential barrier, the length of the stress range, increasing the region of time dependence of glass strength in the medium, are derived. The Rehbidner constant in the equation describing the effect of the medium on the process of fracture was calculated. The quantitative calculations for on organic glass in the vapour of vacuum oil and PVC in water are given and are in agreement with experiment.
TL;DR: In this article, a model of the lipid bilayer is described, which consists of a system of interacting aliphatic chains tied by one of the ends to a flat impermeable surface and capable of shifting along it.
Abstract: A model of the lipid bilayer is described constituting a system of interacting aliphatic chains tied by one of the ends to a flat impermeable surface and capable of shifting along it. To maintain constant density periodic boundary conditions are introduced. The transitions between states (conformational changes of the chains and their disposition within the isolated cell) have been simulated with a computer by the Monte Carlo method. The details of chemical structure of the chains, the braking and correlation of internal rotations and the fluctuation of the valent and torsional angles are taken into account. Depending on the area A per chain the author has calculated the mean square size of the chains 〈r2〉), the parameter of the orientation order S and the mean number of the contacts between the monomer units 〈W〉 and the characteristics of the distribution of the monomer units in space (g2(R), ϱ1, etc.). It is shown that with fall in A (starting from A ∼ 〈r2〉0 where the value 〈r2〉0 refers to the isolated chain tied by an end to the impermeable surface) the system passes into the state with a clearly marked orientation ordering of the chains. The main role is played by the steric interactions of the chains. On the basis of the theory of similitude it is shown that for A ⪡ 〈r2〉0, 〈r2〉 ∼ l 103 N2 (p/A)23 and S∼l43 (p/A)23 (l is length of the skeletal bond; N is the number of bonds in the chain; p=a/d; a is the persistent length; d, the diameter of the chain). The expressions obtained are compared with the data of computer calculation and the experimental findings.
TL;DR: In this paper, the temperature shifts of the equatorial and meridional X-ray reflexions of PE, polycaproamide and PVA have been measured in the region 5-400 K. Gradual excitation of the torsional and bending vibrations has been established leading to transverse expansion and longitudinal compression of the crystallite lattice.
Abstract: The temperature shifts of the equatorial and meridional X-ray reflexions of PE, polycaproamide and PVA have been measured in the region 5–400 K. Gradual excitation of the torsional and bending vibrations has been established leading to transverse expansion and longitudinal compression of the crystallite lattice. The characteristic temperatures of the vibrations have been evaluated. The expansion coefficients are compared for the polymers considered with different intermolecular interaction.
TL;DR: In this paper, a study was made of the kinetics of interaction of m-chlorophenylisocyanate with oligobutadienols, and it was shown that the second order reaction rate constants decreases with a reduction in the concentration of OH groups.
Abstract: A study was made of kinetics of interaction of m-chlorophenylisocyanate with oligobutadienols and oligobutadienediols of different molecular weights in the interval of 323–342°K. It was shown that the second order reaction rate constants decreases with a reduction in the concentration of OH groups. Using kinetic and spectroscopic data a study was made of the effect on the rate of interaction of OH groups with each other and with π-electrons of CC bonds of oligomer. Heat effects of urethane formation were determined.
TL;DR: In this article, the flow birefrigence, diffusion, sedimentation and intrinsic viscosity have been studied of 28 fractions of cellulose dinitrate (CDN) solutions with a 12·1% nitrogen content.
Abstract: The flow birefrigence, diffusion, sedimentation and the intrinsic viscosity have been studied of 28 fractions of cellulose dinitrate (CDN) solutions with a 12·1% nitrogen content. The comparison of the results with the molecular characteristics of cellulose nitrate samples having a differing N-content has shown that an increase of the nitro-groups increases the rigidity equilibrium and the absolute optical anistropy of the monomer chain unit present in cellulose nitrates.
TL;DR: In this paper, the authors measured the moduli of elasticity and the equilibrium degrees of swelling of the gels themselves and the dry networks obtained from them as a function of the molecular mass of the crosslinked oligomer and the concentration of the polymer at the moment of crosslinkage.
Abstract: The authors have investigated gels based on regular networks obtained by crosslinking α,ω-dihydroxyoligodimethylsiloxane at different degrees of dilution in solution. They measured the moduli of elasticity and the equilibrium degrees of swelling of the gels themselves and the dry networks obtained from them as a function of the molecular mass of the crosslinked oligomer and the concentration of the polymer at the moment of crosslinkage. The values of the molecular mass obtained from these data between the nodes M c are compared with the actual M c set by the molecular mass of the crosslinked oligomer. The conditions of applicability of the theory of high elasticity and the limits of the possible regulation of the properties of the gels and “dry” networks by changing the conditions of crosslinkage are demonstrated.
TL;DR: In this article, the changes in crystalline polymers caused by simultaneous action of high pressures and shear strains were studied by differential scanning calorimetry, and it was shown that the crystallinity of some polymers may be increased as a result of high pressure treatment.
Abstract: The changes in crystalline polymers, caused by simultaneous action of high pressures and shear strains, have been studied by differential scanning calorimetry. Polymer treatments were performed at room temperature and 5–60 kbars pressure. HDPE, LDPE, PP, PEO polycaproamide, PETPh, polybutylene terephthate, polyurethane and some blends of these polymers were studied. A new peak was found in the thermograms of polymers which have a glass transition point below room temperature. It was shown that the crystallinity of some polymers may be increased as a result of high pressure treatment.
TL;DR: In this paper, the non-equilibrium anionic copolymerization of hexamethyl cyclotrisiloxane with the stereoisomers of 1,3,5-trimethyl-1, 3, 5-triphenyl cyclotriscoilane was studied and the microstructure of the corresponding copolymers evaluated using first order Markovian statistics combined with the data obtained from the PMR spectra.
Abstract: The non-equilibrium anionic copolymerization of hexamethyl cyclotrisiloxane with the stereoisomers of 1,3,5-trimethyl-1,3,5-triphenyl cyclotrisiloxane has been studied and the microstructure of the corresponding copolymers evaluated using first order Markovian statistics combined with the data obtained from the PMR spectra.
TL;DR: In this article, the authors investigated the cationic polymerization of e-caprolactone initiated by (C 2 H 5 ) 3 O+SbF − in the presence of ethylene glycol at 20-60°C.
Abstract: Kinetic and PMR spectroscopic methods have been used to investigate the cationic polymerization of e-caprolactone initiated by (C 2 H 5 ) 3 O+SbF − in the presence of ethylene glycol at 20–60°C. Alcohols markedly increase the rate of polymerization of e-caprolactone, the process changing to a mechanism in which the polymeric chain grows at end hydroxyl groups through the preliminary transfer of a proton to the monomer (“hydroxo-mechanism”). The difference in the basicity of the hydroxyl groups of the compounds formed in the initial linking of the monomer causes preferential growth of the chain at one of the ends. In such systems, the molecular mass of the polymer is determined by the monomer: addition ratio.
TL;DR: In this article, the main processes occurring on exposure of saturated polymers to ozone and their possible applications in scientific research and technology are considered, and the kinetics and mechanism of the processes of interaction of ozone with the macromolecules in solution and in the solid phase are discussed.
Abstract: The main processes occurring on exposure of saturated polymers to ozone and their possible applications in scientific research and technology are considered. It is shown that the reaction of ozone with the CH bonds of the macromolecules is accompanied by the formation of carbonyl and peroxide functional groups which accumulate parallel and independently of one another. As intermediate products, peroxide radicals are present in the system. The kinetics and mechanism of the processes of interaction of ozone with the macromolecules in solution and in the solid phase are discussed.
TL;DR: In this article, a study was made of the polymerization of butadiene under the action of sodium organic derivatives in hydrocarbon media in the presence of 4,4-dimethyl-1,3-dioxane (DMDO).
Abstract: A study has been made of the polymerization of butadiene under the action of sodium organic derivatives in hydrocarbon media in the presence of 4,4-dimethyl-1,3-dioxane (DMDO). In benzene, ethyl benzene and cyclohexane polymerization occurs quantitatively and a high molecular weight polymer is obtained; in the presence of toluene the MW and (in some cases) the polymer yields are lower as a result of metallation of the solvent. Butadiene polymerization in mixtures of DMDO and hydrocarbons is accompanied by chain termination, apparently as a result of abstraction of a labile acetal hydrogen from DMDO.
TL;DR: In this paper, the interaction between an initiator, 4-azo-bis-4-cyanpentanoic acid, and a calcium carbonate surface, and aspects of polymerization in the presence of a filler which is also a carrier of the active initiating sites have been studied.
Abstract: The interaction between an initiator, 4-azo-bis-4-cyanpentanoic acid, and a calcium carbonate surface, and aspects of polymerization in the presence of a filler which is also a carrier of the active initiating sites have been studied. It has been shown that the kinetic parameters for the initiator's thermal decomposition, for initiation and for the polymerization of various monomers may be substantially altered by the adsorption of the initiator on to the surface of a solid phase.
TL;DR: In this paper, the dependence of ring-formation on the structure of diglycidyl ethers in reactions with aromatic amines is discussed, and the relationship between the probability of ring formation and the equilibrium elasticity of network systems is demonstrated.
Abstract: The dependence of ring-formation on the structure of diglycidyl ethers in reactions with aromatic amines is discussed The structure of the network polymer and the conformational tendency to cyclization in the oligomers under consideration are analysed on the basis of a statistical model An interconnection between the probability of ring-formation and the equilibrium elasticity of the network systems is demonstrated The tendency towards the formation of ring structures in systems based on diglycidyl ortho-ethers has been established experimentally, a fact which is in agreement with the theoretical calculations
TL;DR: In this paper, the interference micromethod has been used to study the phase equilibrium in polyvinyl chloride+linear oligoether acrylates of the p-ethylene and p-oxyethylene dimethacrylate type.
Abstract: The interference micromethod has been used to study the phase equilibrium in the systems polyvinyl chloride+linear oligoether acrylates of the p-ethylene and p-oxyethylene dimethacrylate type. The diagrams of the phase state obtained for all the systems studied are characterized by the presence of an upper critical temperature of dissolution the value of which depends on the chemical nature and the molecular mass of the oligomers. Comparison of the experimental and calculated data shows that the analytical description of the phase diagrams satisfactorily fits into the theory of Flory-Huggins. The chemical nature and length of the chain of the oligoether acrylates studied fundamentally influence the value of the parameter of interaction and its temperature dependence. These factors also influence change in the excess chemical potential, the mixing enthalpy and the non-combinatorial mixing entropy.
TL;DR: In this article, a study has been made of the cold drawing of amorphous polyethyleneterephthalate under strain in an adsorption-active medium as a function of the rate of deformation.
Abstract: A study has been made of the cold drawing of amorphous polyethyleneterephthalate under strain in an adsorption-active medium as a function of the rate of deformation. A relationship has been found between mechanical behaviour of the polymer under a constant rate of deformation in an adsorption-active medium, and processes of formation and development of specific microcracks. The existence of distributions according to microcrack (craze) growth rates revealed the importance of the role played by microdefects and microheterogeneity in the formation and growth of microcracks.
TL;DR: In this article, the phonon theory of strength was examined; these formulae relate the activation energy of mechanical breakdown U0 and coefficient ψ of the formula of Zhurkov long-term strength with Young's modulus and the Gruneisen coefficient.
Abstract: Formulae of the phonon theory of strength were examined; these formulae relate the activation energy of mechanical breakdown U0 and coefficient ψ of the formula of Zhurkov long-term strength with Young's modulus and the Gruneisen coefficient. Oriented fibres based on aromatic para-polyamides, polyamidohydrazides, linear polyarimides and polyacrylnitrile were investigated. Experimental evaluation confirmed the validity of the formulae proposed and enabled dimensions of thermal fluctuations causing failure to be established.
TL;DR: In this article, the polymer crown ethers, cryptands and cyclodextrins were considered and various ways of synthesizing such macromolecular macrocyclic compounds were presented.
Abstract: The paper considers the polymer analogues of the widely known crown ethers, cryptands and cyclodextrins. It presents various ways of synthesizing such macromolecular macrocyclic compounds. It discusses the interaction of the polymer crown ethers, cryptands (including ionites) and their open-chain analogues-polypodands with cations, inorganic and organic anions and neutral molecules. It analyses polycomplexes with the participation of polymer crown ethers and podands. It takes a brief look at the problems of the practical application of macromolecular macrocyclic compounds and their open-chain analogues.
TL;DR: In this article, the authors have determined the size of the crystallites and distortions of the lattice over the temperature range 5-350°K. The possible causes of the observed rise in the level of the distortions in the direction transverse to the molecular axes with fall in temperature are discussed.
Abstract: From the angular diffraction width of the X-ray reflexions 002, 200, 020 and 110 for samples of oriented polyethylene with large (up to 100 nm) and small (∼ 15 nm) crystallities the authors have determined the size of the crystallites and distortions of the lattice over the temperature range 5–350°K. The possible causes of the observed rise in the level of the distortions in the direction transverse to the molecular axes with fall in temperature are discussed.
TL;DR: In this paper, the results of study of the processes of intramolecular structuring in comb-like polymers using the dielectric polarization method are generalized, and it is shown that unlike the usual flexible-chain linear polymers, the macromolecules of comb-based polymers are characterized by the presence of an intramolescular structure.
Abstract: The results of study of the processes of intramolecular structuring in comb-like polymers using the dielectric polarization method are generalized. It is shown that unlike the usual flexible-chain linear polymers the macromolecules of comb-like polymers are characterized by the presence of an intramolecular structure. This phenomenon predetermines the processes of molecular structuring at supermolecular level too, which may be used in study of the nature of the liquid-crystalline states of polymers.