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1977 Kargin Lectures
REPORTS 1977 KARGIN LECTURES P . V. KOZLOV* THE recent Kargin lectures organized, as in previous years, by the Scientific Council on High Molecular Weight Compounds attached to the Department of General a n d Technical Chemistry, U.S.S.R. Academy of Sciences, the Chemistry faculty of the M. V. Lomonosov State University, Moscow, the L. Ya. Karpov Scientific Research I n s t i t u t e of Physical Chemistry, the A. V. Topchiyev I n s t i t u t e of Petrochemical Synthesis, U.S.S.R. Academy of Sciences and the V. A. Kargin Scientific Research Institute of Polymer Chemistry a n d Technology--were held between 24 and 26 J a n u a r y , 1977. These lectures which coincided with the 70th birthday of V. A. Kargin and were therefore jubilee lectures, became a great forum of Soviet polymer science. 22 Papers were read which reflected most important trends of Soviet chemistry, physical chemistry and physics of high molecular weight compounds. Opening the Kargin lectures K. A. Andrianov, the Chairman of the Scientific Council on High Molecular Weight Compounds, U.S.S.R. Acexlemy of Sciences commented on the jubilee n a t u r e of these lectures a n d described the role of V. A. K a r t i n in the development of polymer science and polymer industry in this country. "The more the inevitable lapse of time divides us from living contact with Valentin Alekseyevich Kargin -- said K. A. Andrianov in conclusion--the deeper and wider the original wisdom and h u m a n i t y of this remarkable scientist appear to us." P. V. Kozlov read a paper on the creative work of V. A. Kargin on the morning session of 24 J a n u a r y . He gave full description of the scientific influence of V. A. Kargin on polymer science, described his significant and organizational work and dealt with the educational a n d public activity of this great Soviet scientist. N. M. Emanuel', V. A. K a b a n o v and S. R. Rafikov read papers in the same morning session. N. M. E m a n u c l ' read a paper "Structural and Kinetic Aspects of Breakdown and Stabilization of Polymers". He noted that prediction of the service life of polymer products under given conditions and operation, stabilization for a given period and finally stabilization, in order to obtain m a x i m u m durability were the main problems of scientific and technical progress in the theory and practice of stabilizing polymers. These problems could only be solved on the basis of quantitative kinetic theory. The relation between reaction kinetics and kinetics of molecular motion, primarily determined b y the physical structure of the polymer and its relaxation properties, is a special feature of chemical reactions in solid polymers. The problem of reactivity in solid polymers therefore is basically the establishment of the physical mechanisms of this bond and of kinetic theory giving a quantiative description of this effect. The relation between reactivity and physical structure and relaxation properties of polymers explained m a n y kinetic anomalies of solid phase reactions: the effect of supermoleeular structure a n d mechanical stress on thermal and oxidizing stability of polymers, the effect of external pressure a n d plasticization of polymers on radical reaction kinetics of chain * Vysokomol. soyed. A19: No. 8, 1903-1909, 1977. 2181
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extension and rupture in oxidation, the extensive distribution of rate constants and activat i e n energies and stepivise kinetics, the compensation effect, high activation energy of solid phase reactions, compared with reactions in the gaseous and liquid phases. Concrete examples were given in the paper, which illustrated these features of reactions in polymers. The structural micro-heterogeneity of polymers results in irregular distribution of reagents, considerable difference in average and local con centrations of macro-radicals, low molecular weight products and stabilizers, reactions in local regions--macro-reactors. A study was made of the effect of these factors on polymer breakdown and stabilization. The relation between reactivity and the structural and physical behaviour of polymers opens up new methods of controlling polymer stability and the efficiency of stabilizers by forming a given supermolecular structure, polymer orientation, b y mechanical stress and othe r effects. The physice-chemical aspects of ageing and stabilization are closely linked i n these ranges with the chemical technology of processing polymers. V. A. K a b a n o v ' s paper entitled "Catalysis with Active Cntres, Immobilized in Polymer Gels" described a new type of composite metal catalytic system, in which active centres are immobilized in the solid by special swelling mosaic polymer gel particles. Catalysts thus combine the advantages of homogeneous contact catalysts. The reaction catalysed not only takes place on the surface, b u t also internally in the swollen polymer particle. The specific effect of active centres used and immobilized in gel therefore may be as high as in homogeneous catalysis. Reaction products may therefore be easily removed from the catalyst phase formed, for example, as fairly strong elastic granules and removed from the reaction zone as a solutio~ n o t contaminated b y components of the catalytic system. Gel-like catalytic systems were used for polymerization of ethylene and other unsaturated hydrocarbons. A n exclusively high stability and selectivity is their distinguishing feature. The paper describes physical and chemical prerequisities of these very important properties. I t was shown, in particular, that during polymerization of ethylene new systems have a prolonged effect for hundreds of hours at 140-200 °, whereas active centres of the same type b u t not immobilized in gel, disappear in a few minutes at given temperatures. Using the principle of immobilization in gel enables composite organo-metallic catalysts to be converted from systems which can only act once and become transformed to stable contact catalysts. The paper b y S. R. Rafikov was concerned with thermal conversion of heat resistant polymers. These conversions normally take place in the polymers indicated in the diffusion range b y a very complex mechanism and are accompanied by the simultaneous separation of low molecular weight substances and structure formation in the polymer residue. Processes of breakdown and structure formation are the consequence of stepwise and parallel reactions, which are due to hemolytic and heterolytic mechanisms. The lecturer proposed a new principle for the stabilization of beat resistant polymers b y the addition to the macromolecule (or polymer system) of structures or stable compounds, which can active or breakdown at high temperatures and interest with active centres (with macroradicals or reactive groups) of the macromolecule. Iqumereus examples are given of the effective stabilization of polyarylenes, polyheteroarylenes and polysiloxanes by the addition of compounds containing halide, carborane, sulphur and metal, or macr0molecular chain structures. The evening session of 24 J a n u a r y , under the chairmanship of V. A. Kabanov, was opened b y a paper by ~T. A. Plate concerning features of the kinetic behaviour of higher alkylmethacrylates during radical polymerization. The paper examined kinetic features of radical bulk polymerization of alkyl methaerylares in tim methyl methacrylate, butyl methacrylatc, octyl methacrylate, dodecyl methacrylate and hexadecyl methacrylate, series. I t was shown that with an increase of the length of the aliphatic ester group, the rate constant of chain rupture regularly decreases; this reduction exceeds two orders of magnitude for hexadecyl methacrylate, compared with me-
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t h y l methacrylate, whereas the rate constant of chain extension and the microstructure of macromolecules formed remain practically constant and independent of the length of the ester group in this series. The life time of the macroradieal is ,~ 90 see for polyhexadecyl methacrylate which renders these systems very similar to "live" radical chains. Results obtained are explained from the point of view of retarded segmental mobility of maeroradieals in chain rupture as a result of structure formatlo~l of the m o n o m e r - - p o l y m e r system undergoing polymerization owing to the interaction of alkyl groups with each other, as is well known for comblike polymers containing long aliphatie branches in each monomer unit. At the same evening session A. lg. Praveduikov expressed his own and I. A. Gritskova's views when he read a paper concerning the rSle of diffusion in emulsion polymerization. I t was noted in the paper t h a t the discrepancy between the S m i t h - E v a r t theory a n d experimental results obtained in polymerization of several monomers in the presence of initiators a n d various emulsifiers is largely due to incorrect selection of parameters which determine the formation of polymer-monomer particles. Experimental results were givor~ in the paper confirming that in emulsion polymerization the concentrations of emulsifier and initiator during the formation of particles are n o t independent variables. The n u m b e r of polymer-monomer particles formed up to the moment of disappearance of the micollar soap will be determined b y the rates of two processes--of initiation and of transfer b y the mieelles of the monomer and emulsifier molecules formed b y latex particles. I t is only when a constant ratio is maintained between emulsifier and initiator in the system t h a t a linear relation is observed between the rate of polymerization and the concentration of the emulsifier. The paper b y N. S. Yenikolopyan about the preparatiou of filled eompositiolm directly during polymerization was read by F. S. D'yaehkovskii. V. A. Kargin considered the problem of creating effective inothods for obtaining a n d processing reinforced and fiUed plastics as one of the most importalXt problems requiring rapid solution. As predicted b y V. A. Kargin, this problem became extremely urgent in recent years. A fundalaentally new method of obtaining filled thermoplastic materials is opened up by the method of polymerizatiolt filling. The principle of this method is that the polymer-filler composition is formed during polymerization initiated on the filler surface. A n y solid inorganic substance m a y be a filler on the surface of which a n y kind of polymerization process is initiated (ionic-coordination, radical, or ionic process). Olefins, dienes, vinyl monomers, acrylates and reactive oligomers m a y be used as monomers. I t is natural that the ratio between filler and polymer can be regulated within wide limits. The method of polymerization filling enables the following problems to be solved: l) compositions with a high degree of filling (up to 90-95% content of inorganic nmterial) can be obtained with a tmiform distribution of polymer in the material; 2) the material can be solidified and its homogeneity increased by filli~lg the open pores and cracks with polymer; 3) the material may be rendered hydrophobic and its corrosion resistauce increased; 4) the problem of capsulating inorganic materials call be solved. Polymerization initiated a n d taking place on the filler surface has a n u m b e r of features correspondillg to kinetic regularities, structure and morphology of the polymer formed. Polymerization filling will, no doubt, enable us to solve importartt practical problems of croatiug highly filled structural materials in the near future. At the morning session on 25th J a n u a r y held trader the chairmanship of Yu. M. Malinskii six papers were read on the various trends in polymer science. The first paper was read b y P. M. Valetskii and was written by him, V. V. Korshak, S. V. Vinogradowa and N. I. Bekasova on the subject "Success in the Chemistry of Materials cor~taining Carborano".
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I t was noted in the paper t h a t the discovery of carborane enabled a now trend to be de= veloped in the field of hetero-organic polymers containing boron and carborane units. Me* thods were developed for the synthesis of carborane monomers, from which linear polyheteroarylene type polymers and reactive, thermo-setting oligomers were obtained. A study was made of the effect of the isomerism of carborano groups and the structure of groups consisting directly of a carborane nucleus on the properties of polymers containing earborane. A study of the properties of these polymers established that the specific behaviour o f polymers containing carborane during heating shows first of all in the formation of three dimensional (crosslinked) structures, where inorganic networks are combined with organio three dimensional macromolecules. This enabled polymers containing carborane to be recommended for the preparation of highly heat-resistant structural materials. The-paper b y Z. A. Rogovina and L. S. Sletkina dealt with fluorine containing cellulose derivatives. I t was noted in the paper that these derivatives are a new type of eompound~ methods of preparation of these compounds have been examined systematically by the authors of this paper in recent years. Experimental results are given concerning the preparation of different classes of cellulose derivatives containing fluorine using modern methods of organic chemistry--acylation with fluoro-ketenes and re-esterification of perfluorocarbo. :¢ylic acid ester with cellulose b y interaction with acid chlorides and l~-methylolamides o f fluorine-substituted cyanuric acids, o-alkylation of ~, fl-unsaturated compounds containing fluorine and synthesis of graft cellulose copolymers with fluoralkyl esters of unsaturated acids. I t was shown t h a t during the synthesis of various cellulose derivatives with a very low degree of substitution of 0.02-0.03, with an a m o u n t of graft polymer of 1.2-1.6 ~o, cellulose materials become non-wettable with water and what is particularly important, with organic oils of low surface tension. The measures and relations established during the synthesis of cellulose derivatives containing fluorine may, no doubt, be also used for obtaining other hetero-organic derivatives of this polysaccharide. Fibres were prepared from a synthetic graft cellulose copolymer with fluoralkylacrylatos. u n d e r industrial conditions, which m a y be used for imparting overalls with oil and water repellent properties for workers engaged in oil refining and petroleum chemistry. T. M. Birshtein read a paper on the investigation of molecular interaction and chain conformation in macromolecular solutions using the method of simulation with eomputers. Methods of computer simulation enable a wide range of problems to be examined involving the effect of segmental interaction on the strhcture of polymer chains and intermolecular structure. A study of the structure of two and three-block copolymers in dilute solutions using selective solvents indicates that individual macromoleeules of two block copolymcrs form a structure with a compressed block, the other one being swollen; these macromolecules combine to form micelles, the nucleus being formed from the precipitated component. I n three block copolymers precipitation of outer blocks produces an open chain struc* ture with compressed blocks at the ends. A network unit consisting of the components precipitated is the intermolecular structure in this case. Simulation of concentrated solutions show that with an increase of concentration, the structure of individual chains approximates to an unperturbed Gaussian sphere, typical o f dilute solutions under 0 conditions. The paper by Kh. U. Usmanov was concerned with studies of the structural and chemical modification of cellulose. The author briefly reviewed experimental investigations under his supervision on structural features of cellulose and cotton fibre and the correlation between structure and operational properties of cellulose materials. Investigations of the relation between the structure of cellulose materials and chemical properties were of special interest. These investigations, started on the initiative of V. A. IKargin, resulted in the development.
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of new original methods for the control of structural formations of cellulose and cotton fibre~ in order to prepare them for chemical processing, increase reactivity in relation to certain types of chemical reaction. A detailed study of.topochemical reactions typical of cellulose enables some of them (e.g. chemical grafting, cross-linking, etc.) to be carried out at an almost supermolecular level. The author considers that on being further developed, these studies, form the basis of the structural and chemical theory of cellulose which determines the scientific principles of chemical processing of cellulose, including chemical modification. S. P. Papkov and M. P. Iovleva read a paper on "Phase Conversions in Solutions of Rigid chain Polymers". The need, which has increased in recent years, for heat resistant materials, mainly prepared from rigid chain polymers aroused interest in tile solutions of these polymers, particularly in phase conversions. A brief description is given of the main theoretical problems involved in the field of concentrated solutions of rigid chain polymers. Among these are problems, such as solubility of rigid chain polymers and the stability of solutions, conditions and specific properties of forming a liquid crystalline state in systems with the participation of rigid chain polymers, effects of inhibited transition from the amorphous to the liquid crystalline and then into the truly crystalline state, morphological features of phase formations during precipitation of polymers from solutions, cases of spontaneous elongation of oriented materials obtained from polymers with increased chain rigidity and some other problems. I t is noted t h a t the ability of rigid chain polymers to undergo self-ordering explains the possibility of achieving a high and stable orientation of macromolecules along the fibre axis, which accounts for the unique strength properties of fibres of rigid chair~ polymers. A. A. Tager was concerned with thermodynamic displacement of polymers and examined methods of determining free energy, the enthalpy and entropy of mixing polymers with each other over the whole range of composition. I t was shown that in spite of existing views, the entropy of mixing of polymers is not zero and may reach high values positive or negative. The author formulated thermodynamic criteria of the mutual solubility of polymers, which equally concern polymer-oligomer and oligomcr-oligomer systems. 1. Mixing entropy should be negative, i.e. polymers should be able to form joint structures. 2. Mixing enthalpy should also be negative (exothermic mixing), which is possible if the energy of interaction of different molecules is higher than that of homogeneous ones. 3. The absolute value of AH should be higher than TAS; here A ~ < 0, i.e. spontaneous mixing occurs. When all the three conditions are fulfilled, the polymers are mutually soluble a n d form stable single phase systems. I f all the three conditions are not fulfilled, the polymers are mutually insoluble and a two phase thermodynamically unstable colloid system is formed. Most polymer-polymer systems occupy an intermediate position. These are two phase systems in a state of metastable equilibrium. From this point of view the stability of polymerpolymer systems is the rule and instability, the exception. I t was pointed out t h a t with a high molecular weight of coinponents to be mixed t h e upper critical temperature is not achieved for polymer-polymer systems. These systems are characterized by a reduction in stability during heating, i.e. have lower critical temperatures of mixing. At the evening session of 25 J a n u a r y held under the chairmanship of A. A. T a t e r three papers were read. I n a joint paper N. F. Bakeyev, A. L. Volynskii and ¥e. A. Sinevich dealt with "Structural and Mechanical Properties of Glassy Polymers" deformed in adsorption active media. The first part of the paper examined experimental restflts of the effect of adsorption active media on the mechanical behaviour of glassy polymers using polystyrene. As a result of analysing the relation between the limit of forced elasticity of polystyrene and the con-
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¢entration of surface active substances, in the dilute solutions of which deformation occured, it was found t h a t this relation conforms to the Duclos-Traub rule. This is evidence of the fact t h a t the effects observed are based on the adsorption reduction of strength, i.e. the Reb i n d e r effect. I n the second part of the paper experimental results were given concerning the structure .and behaviour of some glassy polymers previously deformed in adsorption active media. I t was shown that in this case the polymers acquire a whole n u m b e r of unusual properties. ~rhey show higher reversible deformations below the glass temperature, ability to undergo spontaneous elongation during annealing, etc. To explain the effects observed, a study was made of the structure of these polymers. I t was concluded that the unusual physics a n d mechanical behaviour of polymers deformed in adsorption active media is due to surface effects .and properties of the highly dispersed material formed as a result of micro-cracks growing during the deformation of polymers in liquid media. In the final part of the paper results were described of a study carried out with G. M. Lukovkin concerning fibrillization of polymers during cold drawing using computer simulation, I t was concluded from results t h a t fibrillisation of glassy and crystalline polymers is due t o structural heterogeneity; this causes stress concentration and local deformation. Polymer fibrils should be regarded as statistical units of macromolecules, of which the parameters .depend on the intensity of thermal motion, the elasticity modulus of the initial material a n d molecular interaction. The paper b y Yu. V. Ovchinnikov dealt with structural "ageing" of plasticized polyvinylchlorido. Experimental results of the variation of some physical, mechanical and electrical proporties of plasticized polyvinylchloride during ageing are given over a period of time, these being only due to structural conversions in the polymer-plasticizer system. The type and magnitude of changes in properties as a result of structural ageing are commensurate or .even prevail over changes iin properties of the material as a result of chemical transformations. A study was made of the effect on structural ageing of plasticized polyvinylchloride of t h e type of a plasticizer characterized b y thermodynamic compatibility with the polymer, t h e type of polymer, previous heat treatment and other factors contributing to structural conversions in the polyvinylchloride-plasticizer system. The author interprets the experimental results on the basis of ideas about conformation changes taking place in chain macromoloeules over a period of time, physical states of the polymer a n d plasticizer, interaction of the latter with active groups of the polymer and the heterophase n a t u r e of the system itself. A. I. Slutsker read a paper entitled "Kinetic Micromeehanics of the Decomposition o f Polymers". A study is made of polymer decomposition related to the rupture of chain molecules, bearing in m i n d oriented amorphous-crystalline polymers. There are three stages in the development of this decomposition: 1) rupture of individual macromolee~ules (initiating, 2) formation of crack nuclei, 3) extension of cracks. Conditions of decomposition at all :stages are decisively determited by the supermolecular structure of polymers. Decomposition is examined in detail by a n u m b e r of direct physical and physical and chemical methods. The kinetic n a t u r e of decomposition was established at all stages. Heat motion (thermal fluctuation) determines the from and type of rupture of the stressed polymer molecule. Using experimental results obtained a detailed analysis is made of the elementary stage o f thermal fluctuation rupture of this molecule and its energy a n d strustural consequences. T h e principles of kinetic micro-mechanics of decomposition of polymers are described. Six papers were read at the morning session of 26 J a n u a r y chaired b y A. S. Arzhakov. The paper b y M. M. K o t o u and I. V. Andreyeva " F o r m a t i o n and Transformation of Polymers of U n s a t u r a t e d Aldehydes,, was read b y I. V. Andreyeva.
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I t follows from the paper t h a t polymers were synthesized from unsaturated aldehydes and examined, producing reproducible results; polymer structure was examined in detail. High molecular weight polymers with vinyl type units in t h e main chain were obtained by radical polymerization, anionic polymerization produced vinyl and acetal type units. During polymer synthesis both under conditions of radical polymerization using redox systems and anionic polymerization secondary reactions take place spontaneously with aldehyde groups in polymer chains, namely: polymerization to form cyclic structures, chain transfer and Tishchenko reaction to form lactone structures. A study of causes and the mechanism of ring formation of aldehyde groups in polymer chains made it possible to control this process. The statistical distribution of various lmits in polymer chains was established. MWD-s of modified acrolein polymers obtained using various redox systems were compared. To obtain metacrolein and acrolcin polymers with a high aldehyde group content and yield, methods were proposed for static heterophase polymerization with specific redox systems. Reactions were carried out in polymer chains both to obtain polymers containing hydroxyl and to study disproportionation of aldehyde groups during polymer synthesis. Disproportionation of aldehyde groups on a polymer should be regarded as a polymerization process at the carbonyl group with chain transfer. V. P. Zubov read a paper entitled: "Alternating Copolymerization by a Radical Mechanism". He examined problems of mechanisms of elementary stages of alternating copolymerization and the kinetic description of these reactions, which are of considerable theoretical and practical value. The t y p e of active centre and the mechanism of chain extension could be established for a number of systems by E P R . I t was shown in particular t h a t chain extension in alternating copolymerization m a y be carried out both by stepwise addition of individual monomer molecules and binary complexes to growing macroradicals. In the latter case two types of growing macroradical could exist simultaneously, which did not transfer with accepter and donor end units in a polymerizing system. By copolymerization of vinyl esters with maleic acid derivatives a s tu d y was made of the effect of eomonomer structure on transition from one limiting mechanism of chain extension to aimther and the relation between the mechanism of chain extension and the ability of monomers to form donor-accepter complexes in solution. A study was made of a kinetic system to give ~ quantitative description of alternating copolymorization, which is based on determining the composition of the monomer mixture at the m a x i m u m rate of copolymerization with different monomer concentrations. The system makes it possible, in particular, to determine the effect of adding free monomers and their complexes on the reaction of extension under actual experimental conditions. In his paper V. Ye. Gul' dealt with the principles of adhesive interaction of polymers with metals using general views of adhesive interaction of polymers. Noting that adhesive interaction is due to a reduction of the free surface energy of the adhesive--substrate system, the author emphasized t h a t adhesion is normally evaluated by its inadequate characteristics--specific energy of adhesive decomposition. H e noted t h a t if adhesion A=Si~,~n~U~ (S~ being t h e initial contact surface; h i - - n u m b e r of adhesion bonds; U t - - b o n d energy cf the ith character, respectively), adhesive strength A =K (Sl,~n~U~), where K is a function which reflects conditions of decomposition (rate of separation, temperature, coefficient of excess strain). Comparing the time and temperature relation of adhesive strength and the iuitial contact surface, we demonstrated the mechanism of formation of Sin o v e r a period of time and found it to be micro-rheological for t h e case of adhesion of a polyolefln melt to aluminium f()il. In his paper Yu. S. Lipatov dealt with the structure and properties of mutually penetrating polymer networks (MPN). We examined a new type of polymer composition obtained by forming a three dimensional erosslinked polymer in the matrix of another cross linked polymer. The preparation of these mutually penetrating networks was studied by swelling the network m a t r i x in the reaction system capable of forming a second network. Using MPN
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based on polyurethane a n d a styrene-butadiene copolymer a n d polyurethane and polyuret t ~ e acrylate, thermodynamic parameters characterizing MPN were examined and the proportion evaluated of the transition layer formed as a consequence of the incompatibility of -components during the formation of MPN and onthlapics a n d free energies of mixing two networks, were determined. I t was shown that the transition layer has a marked effect on the structure a n d thermodynamic properties of MPI~, this being a zone where thermodynamic incompatibility of components is observed. Processes of forming MPN are determined to a large extent b y the structure of the network matrix; adsorption interaction with its comp o n e n t s forming the second network, influences conditions of formation of the penetrating network and its structure. Results arc given of investigating a new class of mutually penetrating networks synthe:sized for the first time from oligoester acrylates and a styrene-butadiene benzene eopolymer .obtained b y the mechanism of "live" anionic polymerization. Small angle X-ray scattering was used to determine quantitatively the parameters, which characterize the heterogeneity o f a three dimensional structure and dimensions of heterogeneity. I t was shown that structural heterogeneity of MPN is a factor which determines basic properties. V. A. Ponomarenko read a paper on "Ionic Polymerization of tteterocycles". He examined thoroughly the problems of structure and reactivity of active centres of cationic, .anionic a n d coordination-anionic polymerization of hetor-o cycles. The kinetic isotropic effect using 13C a n d 1~C provides reliable information about the structure of the active centres indicated. Using this method, in particular, experimental proof was obtained for the first time t h a t the cyclic oxonium ion is the active centre in cationic polymerization. The polymer chain has a marked effect on structure, stability and the activity of centres of ionic polymerization. During anionic and coordination-anionic polymerization of ~-oxides, ~-thio-oxides of N-carboxyanhydrides of ~-aminoacids the last units fo the polymer chain form an asymmetrical c o o r d i n a t i o n sphere around the metal and the cation, which is similar to the right and left ~pirals of polypeptides, which accounts for the formation of enantiomorphous active centres, the stability and activity of which depend on the type of metal or cation and the structure of the last 6-10 polymer chain units combined with them, particularly their micro-structure, ~he donor ability of hetero-atoms and the type of lateral groups, The formation of these active ccntres explains not only steroospecific, b u t also stereo-selective polymerization of the heterocycles mentioned during coordination-anionic and anionic polymerization. A paper was read at this session b y V. G. Baranov a n d S. Ya. Frenkel' on "Topomorp h i s m and Phase Dualism of Polymers". Finally, S. A. Arzhakov, member of the Organizing Committee of Kargin Lectures in 1977 summarized these jubilee lectures and noted the broad front of the theme of these lectures, their profoundness and the considerable scientific interest attached to them. "These lectures--said S. A. Arzhakov--refiect a considerable development in fundamental studies ~arried out in the field of polymer science, in this country; they became a true forum of theoretical achievement in macromolecular chemistry a n d p h y s i c s , - being a worthy expression of the memory of V. A. Kargin. S. A. Arzhakov proposed that the next Kargin lectures be held in 1978 in the V. A. Karg i n Scientific Research I n s t i t u t e of Polymer Chemistry and Technology", V. A. Kargin • eing the founder a n d first scientific head of this Institute.
Translated by E. S~.ME~Z
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extension and rupture in oxidation, the extensive distribution of rate constants and activat i e n energies and stepivise kinetics, the compensation effect, high activation energy of solid phase reactions, compared with reactions in the gaseous and liquid phases. Concrete examples were given in the paper, which illustrated these features of reactions in polymers. The structural micro-heterogeneity of polymers results in irregular distribution of reagents, considerable difference in average and local con centrations of macro-radicals, low molecular weight products and stabilizers, reactions in local regions--macro-reactors. A study was made of the effect of these factors on polymer breakdown and stabilization. The relation between reactivity and the structural and physical behaviour of polymers opens up new methods of controlling polymer stability and the efficiency of stabilizers by forming a given supermolecular structure, polymer orientation, b y mechanical stress and othe r effects. The physice-chemical aspects of ageing and stabilization are closely linked i n these ranges with the chemical technology of processing polymers. V. A. K a b a n o v ' s paper entitled "Catalysis with Active Cntres, Immobilized in Polymer Gels" described a new type of composite metal catalytic system, in which active centres are immobilized in the solid by special swelling mosaic polymer gel particles. Catalysts thus combine the advantages of homogeneous contact catalysts. The reaction catalysed not only takes place on the surface, b u t also internally in the swollen polymer particle. The specific effect of active centres used and immobilized in gel therefore may be as high as in homogeneous catalysis. Reaction products may therefore be easily removed from the catalyst phase formed, for example, as fairly strong elastic granules and removed from the reaction zone as a solutio~ n o t contaminated b y components of the catalytic system. Gel-like catalytic systems were used for polymerization of ethylene and other unsaturated hydrocarbons. A n exclusively high stability and selectivity is their distinguishing feature. The paper describes physical and chemical prerequisities of these very important properties. I t was shown, in particular, that during polymerization of ethylene new systems have a prolonged effect for hundreds of hours at 140-200 °, whereas active centres of the same type b u t not immobilized in gel, disappear in a few minutes at given temperatures. Using the principle of immobilization in gel enables composite organo-metallic catalysts to be converted from systems which can only act once and become transformed to stable contact catalysts. The paper b y S. R. Rafikov was concerned with thermal conversion of heat resistant polymers. These conversions normally take place in the polymers indicated in the diffusion range b y a very complex mechanism and are accompanied by the simultaneous separation of low molecular weight substances and structure formation in the polymer residue. Processes of breakdown and structure formation are the consequence of stepwise and parallel reactions, which are due to hemolytic and heterolytic mechanisms. The lecturer proposed a new principle for the stabilization of beat resistant polymers b y the addition to the macromolecule (or polymer system) of structures or stable compounds, which can active or breakdown at high temperatures and interest with active centres (with macroradicals or reactive groups) of the macromolecule. Iqumereus examples are given of the effective stabilization of polyarylenes, polyheteroarylenes and polysiloxanes by the addition of compounds containing halide, carborane, sulphur and metal, or macr0molecular chain structures. The evening session of 24 J a n u a r y , under the chairmanship of V. A. Kabanov, was opened b y a paper by ~T. A. Plate concerning features of the kinetic behaviour of higher alkylmethacrylates during radical polymerization. The paper examined kinetic features of radical bulk polymerization of alkyl methaerylares in tim methyl methacrylate, butyl methacrylatc, octyl methacrylate, dodecyl methacrylate and hexadecyl methacrylate, series. I t was shown that with an increase of the length of the aliphatic ester group, the rate constant of chain rupture regularly decreases; this reduction exceeds two orders of magnitude for hexadecyl methacrylate, compared with me-
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t h y l methacrylate, whereas the rate constant of chain extension and the microstructure of macromolecules formed remain practically constant and independent of the length of the ester group in this series. The life time of the macroradieal is ,~ 90 see for polyhexadecyl methacrylate which renders these systems very similar to "live" radical chains. Results obtained are explained from the point of view of retarded segmental mobility of maeroradieals in chain rupture as a result of structure formatlo~l of the m o n o m e r - - p o l y m e r system undergoing polymerization owing to the interaction of alkyl groups with each other, as is well known for comblike polymers containing long aliphatie branches in each monomer unit. At the same evening session A. lg. Praveduikov expressed his own and I. A. Gritskova's views when he read a paper concerning the rSle of diffusion in emulsion polymerization. I t was noted in the paper t h a t the discrepancy between the S m i t h - E v a r t theory a n d experimental results obtained in polymerization of several monomers in the presence of initiators a n d various emulsifiers is largely due to incorrect selection of parameters which determine the formation of polymer-monomer particles. Experimental results were givor~ in the paper confirming that in emulsion polymerization the concentrations of emulsifier and initiator during the formation of particles are n o t independent variables. The n u m b e r of polymer-monomer particles formed up to the moment of disappearance of the micollar soap will be determined b y the rates of two processes--of initiation and of transfer b y the mieelles of the monomer and emulsifier molecules formed b y latex particles. I t is only when a constant ratio is maintained between emulsifier and initiator in the system t h a t a linear relation is observed between the rate of polymerization and the concentration of the emulsifier. The paper b y N. S. Yenikolopyan about the preparatiou of filled eompositiolm directly during polymerization was read by F. S. D'yaehkovskii. V. A. Kargin considered the problem of creating effective inothods for obtaining a n d processing reinforced and fiUed plastics as one of the most importalXt problems requiring rapid solution. As predicted b y V. A. Kargin, this problem became extremely urgent in recent years. A fundalaentally new method of obtaining filled thermoplastic materials is opened up by the method of polymerizatiolt filling. The principle of this method is that the polymer-filler composition is formed during polymerization initiated on the filler surface. A n y solid inorganic substance m a y be a filler on the surface of which a n y kind of polymerization process is initiated (ionic-coordination, radical, or ionic process). Olefins, dienes, vinyl monomers, acrylates and reactive oligomers m a y be used as monomers. I t is natural that the ratio between filler and polymer can be regulated within wide limits. The method of polymerization filling enables the following problems to be solved: l) compositions with a high degree of filling (up to 90-95% content of inorganic nmterial) can be obtained with a tmiform distribution of polymer in the material; 2) the material can be solidified and its homogeneity increased by filli~lg the open pores and cracks with polymer; 3) the material may be rendered hydrophobic and its corrosion resistauce increased; 4) the problem of capsulating inorganic materials call be solved. Polymerization initiated a n d taking place on the filler surface has a n u m b e r of features correspondillg to kinetic regularities, structure and morphology of the polymer formed. Polymerization filling will, no doubt, enable us to solve importartt practical problems of croatiug highly filled structural materials in the near future. At the morning session on 25th J a n u a r y held trader the chairmanship of Yu. M. Malinskii six papers were read on the various trends in polymer science. The first paper was read b y P. M. Valetskii and was written by him, V. V. Korshak, S. V. Vinogradowa and N. I. Bekasova on the subject "Success in the Chemistry of Materials cor~taining Carborano".
2184
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I t was noted in the paper t h a t the discovery of carborane enabled a now trend to be de= veloped in the field of hetero-organic polymers containing boron and carborane units. Me* thods were developed for the synthesis of carborane monomers, from which linear polyheteroarylene type polymers and reactive, thermo-setting oligomers were obtained. A study was made of the effect of the isomerism of carborano groups and the structure of groups consisting directly of a carborane nucleus on the properties of polymers containing earborane. A study of the properties of these polymers established that the specific behaviour o f polymers containing carborane during heating shows first of all in the formation of three dimensional (crosslinked) structures, where inorganic networks are combined with organio three dimensional macromolecules. This enabled polymers containing carborane to be recommended for the preparation of highly heat-resistant structural materials. The-paper b y Z. A. Rogovina and L. S. Sletkina dealt with fluorine containing cellulose derivatives. I t was noted in the paper that these derivatives are a new type of eompound~ methods of preparation of these compounds have been examined systematically by the authors of this paper in recent years. Experimental results are given concerning the preparation of different classes of cellulose derivatives containing fluorine using modern methods of organic chemistry--acylation with fluoro-ketenes and re-esterification of perfluorocarbo. :¢ylic acid ester with cellulose b y interaction with acid chlorides and l~-methylolamides o f fluorine-substituted cyanuric acids, o-alkylation of ~, fl-unsaturated compounds containing fluorine and synthesis of graft cellulose copolymers with fluoralkyl esters of unsaturated acids. I t was shown t h a t during the synthesis of various cellulose derivatives with a very low degree of substitution of 0.02-0.03, with an a m o u n t of graft polymer of 1.2-1.6 ~o, cellulose materials become non-wettable with water and what is particularly important, with organic oils of low surface tension. The measures and relations established during the synthesis of cellulose derivatives containing fluorine may, no doubt, be also used for obtaining other hetero-organic derivatives of this polysaccharide. Fibres were prepared from a synthetic graft cellulose copolymer with fluoralkylacrylatos. u n d e r industrial conditions, which m a y be used for imparting overalls with oil and water repellent properties for workers engaged in oil refining and petroleum chemistry. T. M. Birshtein read a paper on the investigation of molecular interaction and chain conformation in macromolecular solutions using the method of simulation with eomputers. Methods of computer simulation enable a wide range of problems to be examined involving the effect of segmental interaction on the strhcture of polymer chains and intermolecular structure. A study of the structure of two and three-block copolymers in dilute solutions using selective solvents indicates that individual macromoleeules of two block copolymcrs form a structure with a compressed block, the other one being swollen; these macromolecules combine to form micelles, the nucleus being formed from the precipitated component. I n three block copolymers precipitation of outer blocks produces an open chain struc* ture with compressed blocks at the ends. A network unit consisting of the components precipitated is the intermolecular structure in this case. Simulation of concentrated solutions show that with an increase of concentration, the structure of individual chains approximates to an unperturbed Gaussian sphere, typical o f dilute solutions under 0 conditions. The paper by Kh. U. Usmanov was concerned with studies of the structural and chemical modification of cellulose. The author briefly reviewed experimental investigations under his supervision on structural features of cellulose and cotton fibre and the correlation between structure and operational properties of cellulose materials. Investigations of the relation between the structure of cellulose materials and chemical properties were of special interest. These investigations, started on the initiative of V. A. IKargin, resulted in the development.
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of new original methods for the control of structural formations of cellulose and cotton fibre~ in order to prepare them for chemical processing, increase reactivity in relation to certain types of chemical reaction. A detailed study of.topochemical reactions typical of cellulose enables some of them (e.g. chemical grafting, cross-linking, etc.) to be carried out at an almost supermolecular level. The author considers that on being further developed, these studies, form the basis of the structural and chemical theory of cellulose which determines the scientific principles of chemical processing of cellulose, including chemical modification. S. P. Papkov and M. P. Iovleva read a paper on "Phase Conversions in Solutions of Rigid chain Polymers". The need, which has increased in recent years, for heat resistant materials, mainly prepared from rigid chain polymers aroused interest in tile solutions of these polymers, particularly in phase conversions. A brief description is given of the main theoretical problems involved in the field of concentrated solutions of rigid chain polymers. Among these are problems, such as solubility of rigid chain polymers and the stability of solutions, conditions and specific properties of forming a liquid crystalline state in systems with the participation of rigid chain polymers, effects of inhibited transition from the amorphous to the liquid crystalline and then into the truly crystalline state, morphological features of phase formations during precipitation of polymers from solutions, cases of spontaneous elongation of oriented materials obtained from polymers with increased chain rigidity and some other problems. I t is noted t h a t the ability of rigid chain polymers to undergo self-ordering explains the possibility of achieving a high and stable orientation of macromolecules along the fibre axis, which accounts for the unique strength properties of fibres of rigid chair~ polymers. A. A. Tager was concerned with thermodynamic displacement of polymers and examined methods of determining free energy, the enthalpy and entropy of mixing polymers with each other over the whole range of composition. I t was shown that in spite of existing views, the entropy of mixing of polymers is not zero and may reach high values positive or negative. The author formulated thermodynamic criteria of the mutual solubility of polymers, which equally concern polymer-oligomer and oligomcr-oligomer systems. 1. Mixing entropy should be negative, i.e. polymers should be able to form joint structures. 2. Mixing enthalpy should also be negative (exothermic mixing), which is possible if the energy of interaction of different molecules is higher than that of homogeneous ones. 3. The absolute value of AH should be higher than TAS; here A ~ < 0, i.e. spontaneous mixing occurs. When all the three conditions are fulfilled, the polymers are mutually soluble a n d form stable single phase systems. I f all the three conditions are not fulfilled, the polymers are mutually insoluble and a two phase thermodynamically unstable colloid system is formed. Most polymer-polymer systems occupy an intermediate position. These are two phase systems in a state of metastable equilibrium. From this point of view the stability of polymerpolymer systems is the rule and instability, the exception. I t was pointed out t h a t with a high molecular weight of coinponents to be mixed t h e upper critical temperature is not achieved for polymer-polymer systems. These systems are characterized by a reduction in stability during heating, i.e. have lower critical temperatures of mixing. At the evening session of 25 J a n u a r y held under the chairmanship of A. A. T a t e r three papers were read. I n a joint paper N. F. Bakeyev, A. L. Volynskii and ¥e. A. Sinevich dealt with "Structural and Mechanical Properties of Glassy Polymers" deformed in adsorption active media. The first part of the paper examined experimental restflts of the effect of adsorption active media on the mechanical behaviour of glassy polymers using polystyrene. As a result of analysing the relation between the limit of forced elasticity of polystyrene and the con-
'2186
P.V. KozLov
¢entration of surface active substances, in the dilute solutions of which deformation occured, it was found t h a t this relation conforms to the Duclos-Traub rule. This is evidence of the fact t h a t the effects observed are based on the adsorption reduction of strength, i.e. the Reb i n d e r effect. I n the second part of the paper experimental results were given concerning the structure .and behaviour of some glassy polymers previously deformed in adsorption active media. I t was shown that in this case the polymers acquire a whole n u m b e r of unusual properties. ~rhey show higher reversible deformations below the glass temperature, ability to undergo spontaneous elongation during annealing, etc. To explain the effects observed, a study was made of the structure of these polymers. I t was concluded that the unusual physics a n d mechanical behaviour of polymers deformed in adsorption active media is due to surface effects .and properties of the highly dispersed material formed as a result of micro-cracks growing during the deformation of polymers in liquid media. In the final part of the paper results were described of a study carried out with G. M. Lukovkin concerning fibrillization of polymers during cold drawing using computer simulation, I t was concluded from results t h a t fibrillisation of glassy and crystalline polymers is due t o structural heterogeneity; this causes stress concentration and local deformation. Polymer fibrils should be regarded as statistical units of macromolecules, of which the parameters .depend on the intensity of thermal motion, the elasticity modulus of the initial material a n d molecular interaction. The paper b y Yu. V. Ovchinnikov dealt with structural "ageing" of plasticized polyvinylchlorido. Experimental results of the variation of some physical, mechanical and electrical proporties of plasticized polyvinylchloride during ageing are given over a period of time, these being only due to structural conversions in the polymer-plasticizer system. The type and magnitude of changes in properties as a result of structural ageing are commensurate or .even prevail over changes iin properties of the material as a result of chemical transformations. A study was made of the effect on structural ageing of plasticized polyvinylchloride of t h e type of a plasticizer characterized b y thermodynamic compatibility with the polymer, t h e type of polymer, previous heat treatment and other factors contributing to structural conversions in the polyvinylchloride-plasticizer system. The author interprets the experimental results on the basis of ideas about conformation changes taking place in chain macromoloeules over a period of time, physical states of the polymer a n d plasticizer, interaction of the latter with active groups of the polymer and the heterophase n a t u r e of the system itself. A. I. Slutsker read a paper entitled "Kinetic Micromeehanics of the Decomposition o f Polymers". A study is made of polymer decomposition related to the rupture of chain molecules, bearing in m i n d oriented amorphous-crystalline polymers. There are three stages in the development of this decomposition: 1) rupture of individual macromolee~ules (initiating, 2) formation of crack nuclei, 3) extension of cracks. Conditions of decomposition at all :stages are decisively determited by the supermolecular structure of polymers. Decomposition is examined in detail by a n u m b e r of direct physical and physical and chemical methods. The kinetic n a t u r e of decomposition was established at all stages. Heat motion (thermal fluctuation) determines the from and type of rupture of the stressed polymer molecule. Using experimental results obtained a detailed analysis is made of the elementary stage o f thermal fluctuation rupture of this molecule and its energy a n d strustural consequences. T h e principles of kinetic micro-mechanics of decomposition of polymers are described. Six papers were read at the morning session of 26 J a n u a r y chaired b y A. S. Arzhakov. The paper b y M. M. K o t o u and I. V. Andreyeva " F o r m a t i o n and Transformation of Polymers of U n s a t u r a t e d Aldehydes,, was read b y I. V. Andreyeva.
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I t follows from the paper t h a t polymers were synthesized from unsaturated aldehydes and examined, producing reproducible results; polymer structure was examined in detail. High molecular weight polymers with vinyl type units in t h e main chain were obtained by radical polymerization, anionic polymerization produced vinyl and acetal type units. During polymer synthesis both under conditions of radical polymerization using redox systems and anionic polymerization secondary reactions take place spontaneously with aldehyde groups in polymer chains, namely: polymerization to form cyclic structures, chain transfer and Tishchenko reaction to form lactone structures. A study of causes and the mechanism of ring formation of aldehyde groups in polymer chains made it possible to control this process. The statistical distribution of various lmits in polymer chains was established. MWD-s of modified acrolein polymers obtained using various redox systems were compared. To obtain metacrolein and acrolcin polymers with a high aldehyde group content and yield, methods were proposed for static heterophase polymerization with specific redox systems. Reactions were carried out in polymer chains both to obtain polymers containing hydroxyl and to study disproportionation of aldehyde groups during polymer synthesis. Disproportionation of aldehyde groups on a polymer should be regarded as a polymerization process at the carbonyl group with chain transfer. V. P. Zubov read a paper entitled: "Alternating Copolymerization by a Radical Mechanism". He examined problems of mechanisms of elementary stages of alternating copolymerization and the kinetic description of these reactions, which are of considerable theoretical and practical value. The t y p e of active centre and the mechanism of chain extension could be established for a number of systems by E P R . I t was shown in particular t h a t chain extension in alternating copolymerization m a y be carried out both by stepwise addition of individual monomer molecules and binary complexes to growing macroradicals. In the latter case two types of growing macroradical could exist simultaneously, which did not transfer with accepter and donor end units in a polymerizing system. By copolymerization of vinyl esters with maleic acid derivatives a s tu d y was made of the effect of eomonomer structure on transition from one limiting mechanism of chain extension to aimther and the relation between the mechanism of chain extension and the ability of monomers to form donor-accepter complexes in solution. A study was made of a kinetic system to give ~ quantitative description of alternating copolymorization, which is based on determining the composition of the monomer mixture at the m a x i m u m rate of copolymerization with different monomer concentrations. The system makes it possible, in particular, to determine the effect of adding free monomers and their complexes on the reaction of extension under actual experimental conditions. In his paper V. Ye. Gul' dealt with the principles of adhesive interaction of polymers with metals using general views of adhesive interaction of polymers. Noting that adhesive interaction is due to a reduction of the free surface energy of the adhesive--substrate system, the author emphasized t h a t adhesion is normally evaluated by its inadequate characteristics--specific energy of adhesive decomposition. H e noted t h a t if adhesion A=Si~,~n~U~ (S~ being t h e initial contact surface; h i - - n u m b e r of adhesion bonds; U t - - b o n d energy cf the ith character, respectively), adhesive strength A =K (Sl,~n~U~), where K is a function which reflects conditions of decomposition (rate of separation, temperature, coefficient of excess strain). Comparing the time and temperature relation of adhesive strength and the iuitial contact surface, we demonstrated the mechanism of formation of Sin o v e r a period of time and found it to be micro-rheological for t h e case of adhesion of a polyolefln melt to aluminium f()il. In his paper Yu. S. Lipatov dealt with the structure and properties of mutually penetrating polymer networks (MPN). We examined a new type of polymer composition obtained by forming a three dimensional erosslinked polymer in the matrix of another cross linked polymer. The preparation of these mutually penetrating networks was studied by swelling the network m a t r i x in the reaction system capable of forming a second network. Using MPN
~188
,
P.V.
KOZLOV
based on polyurethane a n d a styrene-butadiene copolymer a n d polyurethane and polyuret t ~ e acrylate, thermodynamic parameters characterizing MPN were examined and the proportion evaluated of the transition layer formed as a consequence of the incompatibility of -components during the formation of MPN and onthlapics a n d free energies of mixing two networks, were determined. I t was shown that the transition layer has a marked effect on the structure a n d thermodynamic properties of MPI~, this being a zone where thermodynamic incompatibility of components is observed. Processes of forming MPN are determined to a large extent b y the structure of the network matrix; adsorption interaction with its comp o n e n t s forming the second network, influences conditions of formation of the penetrating network and its structure. Results arc given of investigating a new class of mutually penetrating networks synthe:sized for the first time from oligoester acrylates and a styrene-butadiene benzene eopolymer .obtained b y the mechanism of "live" anionic polymerization. Small angle X-ray scattering was used to determine quantitatively the parameters, which characterize the heterogeneity o f a three dimensional structure and dimensions of heterogeneity. I t was shown that structural heterogeneity of MPN is a factor which determines basic properties. V. A. Ponomarenko read a paper on "Ionic Polymerization of tteterocycles". He examined thoroughly the problems of structure and reactivity of active centres of cationic, .anionic a n d coordination-anionic polymerization of hetor-o cycles. The kinetic isotropic effect using 13C a n d 1~C provides reliable information about the structure of the active centres indicated. Using this method, in particular, experimental proof was obtained for the first time t h a t the cyclic oxonium ion is the active centre in cationic polymerization. The polymer chain has a marked effect on structure, stability and the activity of centres of ionic polymerization. During anionic and coordination-anionic polymerization of ~-oxides, ~-thio-oxides of N-carboxyanhydrides of ~-aminoacids the last units fo the polymer chain form an asymmetrical c o o r d i n a t i o n sphere around the metal and the cation, which is similar to the right and left ~pirals of polypeptides, which accounts for the formation of enantiomorphous active centres, the stability and activity of which depend on the type of metal or cation and the structure of the last 6-10 polymer chain units combined with them, particularly their micro-structure, ~he donor ability of hetero-atoms and the type of lateral groups, The formation of these active ccntres explains not only steroospecific, b u t also stereo-selective polymerization of the heterocycles mentioned during coordination-anionic and anionic polymerization. A paper was read at this session b y V. G. Baranov a n d S. Ya. Frenkel' on "Topomorp h i s m and Phase Dualism of Polymers". Finally, S. A. Arzhakov, member of the Organizing Committee of Kargin Lectures in 1977 summarized these jubilee lectures and noted the broad front of the theme of these lectures, their profoundness and the considerable scientific interest attached to them. "These lectures--said S. A. Arzhakov--refiect a considerable development in fundamental studies ~arried out in the field of polymer science, in this country; they became a true forum of theoretical achievement in macromolecular chemistry a n d p h y s i c s , - being a worthy expression of the memory of V. A. Kargin. S. A. Arzhakov proposed that the next Kargin lectures be held in 1978 in the V. A. Karg i n Scientific Research I n s t i t u t e of Polymer Chemistry and Technology", V. A. Kargin • eing the founder a n d first scientific head of this Institute.
Translated by E. S~.ME~Z