XVIII international symposium on macromolecular chemistry in Japan (Conclusion)

XVIII INTERNATIONAL SYMPOSIUM ON MACROMOLECULAR CHEMISTRY IN JAPAN (Conclusion)* I. YA. PODDUB~TYI, ~ . A. SLOVOKHOTOVAand B. P. SttTARKMA~ THE sections "Physical Properties of Polymers in Solution" occupied an important place in the work of the Symposium. Approximately 60 papers were presented at this section in addition to two papers read by P. Flory (U.S.A.) on the theme "Thermodynamics of Polymer Solutions" and Sh. Sodron (France) on "Physico-chemical Properties of Chain Maeromolecules in Solution". Both in the main papers and in a considerable number of sectional papers delivered general problems were discussed on the theory of polymer solutions, whereby the m a j o r i t y was characterized by a clearly marked tendency of transition from the idealized models to the calculation of maeromolecular parameters, for which the model is closest to real polymers and by a tendency to find accurate solutions of equations which link the thermodynamic and hydrodynamic behaviour of polymers in solution with the dimensions and shape of macromolecules. In R. Kirst's paper (German Federal Republic) a method was proposed for the calculation of the second virial coefficient o f osmotic pressure (A~), in which the Zimm and Kasass (J. Chem. Phys. 14: 164, 1946; 13: 800, 1959) equation was numerically solved for a persistent chain model of certain thickness. This approach enables a stricter theoretical t r eat m en t of A~ to be developed. Closely linked with this problems is Kh. Y a m a k a v a ' s (Japan) paper in which an a t t e m p t was made to develop a general theory of volumetric expansion ("swelling") of polymer chains expressed by a known coefficient, u, in which the effect of proximity on the excluded volume, v e r y strongly apparent in the case of rigid chains, is taken into account. The theory developed by Aleksandrovich (Israel) of the effect of excluded volume on macromolecular dimensions, based on the assumption of Gaussian distribution of contacts between the segments, is in satisfactory agreement with experimental data when a does not exceed two. Since for a > 2 no experimental data are so far available, it is difficult to judge the advantages of this theory. A group of papers was devoted to the theory of viscosity of polymer solutions. K. Kalide (Japan) from the analysis of equations showing the dependence of intrinsic viscosity on molecular weight, derived from various theories, or their combinations, formulated on equation system which links the values of Km and a in the equation [tl]~KmMa. These equations contain two parameters: Kin, which characterizes polymer configuration and a, dependent on the range of molecular weights in which the measurements were made. The theory developed facilitates this t r eat m en t of experimental data by which it is possible to calculate parameter Km and the limits within which this theory can be applied. The equations proposed fulfil their purpose for many polymers; they show a deviation from the theory for cellulose nitrates which is due to the washability of the spheres. I n the paper by M. Kurat, M. F u k a ts u and K. Osaki (Japan) it was pointed out t h a t in the K i r k w o o d - R a i z m a n approximation the ratio of intrinsic viscosity in t%solvents of annular macromoleeules to the intrinsic viscosity of linear molecules of the same molecular weight is 0.645. I n Ya. Y a m a g a t a ' s (Japan) paper a report was given of the anomaly in the concentration dependence of the viscosity of polystyrene solutions in toluene at very high dilution. In the author's view, it can be interpreted as the consequence of fully hydrodynamic isolation of spheres at very low concentrations. * Vysokomol. soyed. A9: No. 4, 956-968, 1967. 1070

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In the paper by G. Ferry and L. Holmes (U.S.A.) results are given of an investigation o f the features of Newtonian viscosity of polymer solutions; the data obtained were compared with the theories of Rouse (J. Chem. Phys. 21: 1272, 1953) and Zimm (ibid. 24: 269, 1956). The results of investigating the effect of polymer branching on the main parameters in solutions A~[y], the mean-square radius / S ~) and its ratio to the non-perturbed value were discussed in G. Berry's paper (U.S.A.). The author established t h a t the 0-temperature is pratically unaffected by branching; the thermodynamic parameter B, proportional to t h e excluded segment volume, for a branched polymer is less than for a corresponding linear one, and the ratio of (S~r)e/(S[ln)e when the uniformity of branching units is disrupted, becomes greater t h a n the calculated value. Both these effects are explained by the higher segment density near the angle of branching and disappear with very long branches. The effect of the nature of a 0-solvent on the unperturbed dimensions of maeromolecules (using the example of polystyrene) was dealt with in the paper of G. Couvy (Canada). The author established t h a t intrinsic viscosity and consequently the unperturbed molecular dimensions depend on the solubility parameter (specific cohesion) of the mixture Sin, whereby they are characterized by a m a x i m u m for 5m approximately equal to 5 of the polymer. A study of the selective adsorption of solvents by the polymer showed t h a t the main factor determining the differences in undisturbed molecular dimensions is solvent polarity. A very interesting method of obtaining accurate data of values of As and the excluded volume was proposed in the paper by N. Kuvakhara, T. Okazava and M. Kaneko (Japan). The method is based on the measurement of osmotic pressure in the range of moderately concentrated solutions (to a volumetric proportion of polymer of 0.25), for which the heterogeneity of segment distribution no longer exists (compared with the socalled new theory of Flory solutions) and the parameter of polymer-solvent interaction Z has a linear dependence on concentration. F r o m experimental values of )~ the actual value o f excluded segment volume and As can be found. The irrelevance of some main theses of the modern theory of solutions to low-molecular weight polymers was noted in the paper by G. Rossy, E. Bianchi, K. Kuniberti and E. Pedemonte (Italy). F r o m the earlier data derived by the authors and other scientists it follows t h a t the exponent a in the equation [O]--~KM :~ becomes 0.5 and constant K = K o at sufficiently low molecular weights and in good solvents. As in these solvents 0-conditions are not realized, the authors studied As for polystyrene and polymethylmethacrylate in the range of molecular weights for which a ~ 0.5 and the coefficient of volumetric expansion a ~ 1. A considerable increase was observed in A : with a reduction in molecular weight, which is explained by a marked increase in the excluded volume. Such an assumption cannot explain the fact, opposed to all theories, t h a t a = 1 when M ¢ 0 and the authors conelude t h a t the theory of solutions must be reviewed in the case of low-molecular weight polymers. A group of papers was devoted to problems of polymer chain conformation which determines equilibrium and kinetic flexibility. I n some of them, these problems were studied by means of optical rotation and dispersion. Of the results obtained the greatest interest is attached to those discussed in the paper of Ch. Overberger and T. Ioshimura (U.S.A.), according to which, contrary to data already known, synthetic polyamide obtained by condensation of dicarbonylchlorides with o-phenylenediamines has a helical conformation in polar solvents and a spherical one in non-polar solvents. In the lecture b y V. Ye. Eskin (U.S.S.R.) dealing with the complex study of structural conversion in macromolecules of atactic poly-B-vinyl naphthalene it was shown that at a temperature of ~ 60 ° the macromolecules of this atactic polymer in solution change into a state corresponding to lower degree of intramoleeular ordering. Several papers dealt with the structure and properties of rigid macromolecules. Among these, in particular, is the study of the thermody n am i c and hydrodynamic properties of cellulose nitrate solutions, which elucidates the

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anomalous properties of rigid polymers of this class in solution (G. V. Schulz and E. Penz e l - - G e r m a n Federal Republic). A comparative study of the hydrodynamic properties and the optical anisotropy of linear and cyclo-linear polyphenylsiloxanes, which enables the authors to conclude that the cyclo-linear (ladder-type) macromolecules have a high skeletal rigidity, was the subject of the paper by Y. N. Tsvetkov, K. A. Andrianova, Ye. L. Vinogradova, I. N. Shtennikova, S. B. Yakushkina and V. I. Pakhomova (Leningrad). Among the papers dealing with the properties of polyelectrolyte solutions a study of the viscosity of salt solutions of polyacrylic and polymethacrylie acids should be mentioned, which elucidates the problem of the effect of charge density in the solution on the free energy of electrostatic interaction, and correspondingly on the dimensions of poly-ions (I. l~oda, T. Teudzie a n d 1~I. N a g a s a v a - - J a p a n ) . Considerable interest is attached to the paper b y Kh. Inagaki and T. Miyamoto (Japan), in which the relation between the undisturbed dimensions and structures of polymer chains in solution and the ability of the polymer to form single crystals from dilute solutions was considered. The authors directly relate the lower flexibility of polyethylene chains, compared with polypropylene of a n y degree of tactieity, with the considerably greater ease of obtaining polyethylene single crystals. The section devoted considerable attention in its work to problems of the behaviour of bulk and other copolymers in solution. Attempts were made not only to reveal well known anomalies in the properties of bulk and graft copolymer solutions, and also to explain them on a molecular level. I. Kinoshita, D. Frolich and G. Benout (France) reported the results of an investigation into the behaviour of graft copolymers based on polymethylmethacrylate which differ in the number of graft polystyrene chains of a certain molecular weight. The P-temperature of both graft copolymers was the same and was intermediate between the P-temperatures of the corresponding homopolymers. At the same time the rotation radii of both specimens appeared to be different which led to the conclusion that on increasing the spacing density of side branches in P-conditions, volumetric effects do not disappear. A comparison of these results with viscosity data led us to conclude that the macromolecules of the graft copolymers studied have a special shape, so that the polymethylmethacrylate skeleton represents the interior of the sphere, and the branches of polystyrene its surface. The effect of composition on the dimensions of the chain for the case of a statistical styrene-methyl methaerylate copolymer was discussed in the paper of Kh. Nomura and T. Ivachilo (Japan). From light scattering data in a good solvent and the theoretical dependence of the volume expansion coefficient of a sphere ~3 on the excluded segment volume the undisturbed dimensions of copolymers macromolecules were determined; it was shown that the dependence of dimensions on the composition of a statistical copolymer is n o t linear. Preliminary theoretical calculations of the n u m b e r of contacts of the type AA, AB and BB considering the near and distant effect in statistical and block copolymers were made in the paper of M. Lotu-Maga (France). According to the author, the differences in the properties of solutions of these copolymers are directly related to the differences observed in the distribution of the above types of constants. Relatively few papers were presented in the section of new methods of investigating the properties of polymer solutions. However, several papers in this field were of definite interest. A series of papers devoted to chromatographic fractionation of polymers should first be mentioned. I n the paper by G. K a n t o v and E. Siefert (General Federal Republic) the construction of a chromatographic column (operated on the principle of precipitation chromatography) is discussed, in which one P-solvent is used and its dissolving power is gradually changed b y applying a temperature gradient along the column. Plans are being made for the continuous determination of the molecular weight of fractions b y an automatic recording instrument used for the measurement of light scattering. The construction of this device is described in a separate paper b y G. K a n t o v and R. K u n (German Federal Republic).

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For the fractionation of polymers according to molecular weights a method of filtration through gel has recently been successfully used. The filtration mechanism through polymer gels was discussed in the papers of G. Meyerhoff (German Federal Republic) and G. Moor and M. Arrington (U.S.A.). Both authors relate the separation during filtration through a polymer gel of a polymer into fractions of different molecular weights with its pore sizes, so that Moor to prove this compared the statistically evaluated molecular dimensions with the pore dimensions of glass spheres, with which the chromatographic column was filled. I n Kh. Utiyama's paper (Japan), in addition to discussing the theory of light scattering of solutions of flexible polymer chains consisting of anisotropie segments, a new method was proposed to characterize the optical anisotropy of segments from light scattering data. I t was shown that optical anisotropy is very sensitive to the microstructure of the chain. A method of determining polymer diffusion at high temperatures (up to 110 °) using a Tiselius device for eletrophoresis and the Philpot-Svensson optical system, was discussed in the paper by A. Koter, Kh. Matsud, K. Konishi and K. Takemura (Japan). I n the paper by I. Ya. Poddubnyi and V. A. Greehanovskii (U.S.S.R.) by studying the effect during sedimentation of hydrodynamic interaction between the macromolecules on the shape of experimental diagrams, a general equation was derived which describe the expansion of the sedimentation boundary allowing for polydispersion, diffusion and autocompression. A new approach was proposed to calculate the molecular weight distribution (MDW) of polymers b y a rapid ultracentrifuge method. Of undoubted interest is the paper b y M. Doula (U.S.A.) in which for the first time the idea of the macro-mass-spectrometer is proposed. I t is suggested t h a t the polymer should be changed to the state of isolated charged molecules by an "electropulverizer". I n the lecture the possible technical difficulties (low velocity of ions, difficulty in focusing the beam, etc.) and fundamental difficulties (determination of the ratio of charge to mass) are discussed. The possibility of studying m a n y interesting problems renders the development of this device very advisable. The papers b y T. K h o m m and M. Abe (Japan) and R. Zelinskii, O. Mac-Kingley and G. Short (U.S.A.) deal with the study of the molecular structure of elastomers. I n the first equations are derived for the dependence of sedimentation constants and intrinsic viscosity on molecular weight in 0-solvents for cis-polybutadiene, c/s-polyisoprene and butadiene-styrene rubber. I n the second paper data are given concerning the effect of MWD of polybutadiene of a given average molecular weight on the properties of vulcanizates. After the symposium an additional unofficial session on solutions was organized by the section (not included in the programme), with a limited n u m b e r of invited participants. Several papers were read and discussed at this session on the actual problems of investigating the properties of polymer solutions. Several papers dealt with the most urgent problems of investigating the properties of polymer solutions. Numerous papers were devoted to the general problems of the theory of solutions. The most interesting was the paper b y Kh. Y a m a k a v a (Japan) who developed the theory of light scattering b y polymer solutions in mixed solvents from the general theory of scattering b y multicomponent systems and studied conditions for determining true values of M, A2 and ( S ) from the apparent values derived from measurements in mixed solvents. We also note the paper b y G. Berry (U.S.A.), who compared experimental results obtained for characteristic macromoleeular parameters of linear polystyrene with theoretical equations relating these values. T. Kataki's paper (Japan) was devoted to the properties of bulk polymer solutions; this author investigated the dependence of [0] on molecular weight in different P-solvents for statistical and bulk copolymers of styrene with methyl methacrylate and concluded that in the event of A 2 ~ 0 , specific non-Gaussian conformations of spheres are observed for bulk polymers. Two papers were devoted to the investigation of thermodynamic and hydrodynamic properties of low-molecular weight polymers. A detailed review of the problem was contained in the paper of G. Rossi (Italy). Kh. Sotobayashi and ¥ u . Sprin-

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ger (German Federal Republic) in their paper presented the results of an investigation into the intrinsic viscosity and second virial coefficient of styrene and ethylene glycol oligomers (from dimer to M,~ 104). The authors revealed several features in the properties of solutions, due to the transition of macromolecular shape from the stretched rod-shape to the spherical shape. Among the other papers we note the interesting paper b y M. Donkerslut, Zh. Good, Zh. Van-Aartsen and V. Prince (Holland) on the configuration of chains and undisturbed dimensions of polyethylene and isotactic polypropylene. The authors compared the results of their calculations with the experimental data found in the literature and the results of calculations made by other authors. The work of the section showed that the study of physico-chemical properties of solutions continues to occupy a leading place in the general complex of investigations of polymers. At the same time increasing importance is attached to the investigations in the field of conformation conversions of macromolecules of different structures and different degrees and types of ordering, which are directly related to the behaviour of polymers in bulk. The results of modern investigations into polymer structure were generalized in the paper b y A. Keller (Great Britain) entitled "Polymer Crystallinity", M. L. Huggins (U.S.A.) "Modern Investigations of Polymer Structure" and b y O. Vichterl (Czechoslovakia)entitled "Model Compounds as Means of Investigation in Polymer Science" given at the section "Structure of Polymer molecules and Polymer Systems". A. Keller in his paper first dealt with the problem of single crystal polymer structure by repeatedly demonstrating the already known system of polymer chain packing into a folded crystal. Crystalline lattice defects on the surface are bends in the chains during the formation of folds. I n t e r n a l crystal defects can be at the ends of polymer chains. The main defects occur on the crystal surface. Long loops formed by the chains on the crystal surface occur rarely, b u t apparently exist. To prove this, Keller cited several experiments on electron microscopic investigations on molecular weight loss by oxidation or etching b y acids and on the variation of single crystal dimensions. Further, Keller discussed the deformation mechanism of polymer crystals. According to the electron microscopic pattern during compression deformation, the lamellae slide in relation to each other. On injecting the molten specimen, the lamellae are situated almost in parallel on the surface of this specimen at a certain angle to the direction of injection. A measurement of the length of lamellae according to temperature showed that first on increasing temperature the length of lamellae increases and then, before melting of the polymer, a reduction is observed in the length of the lamellae. Problems raised in Keller's paper were discussed in m a n y sectional papers. The paper given b y T. Khama, T. Gore, T. K a v a n a n d C. Maeda, in particular, deals with the detailed study of the structure of polyethylene sigle crystals. I n this paper kinetics of crystallization from dilute solutions of polyethylene fractions of different molecular weights and the morphology of the single crystals obtained were investigated. I t was shown t h a t the rate of crystallization depends on molecular weight a n d that during crystallization additional fractionation of the polymer takes place. I t was also revealed t h a t at the same crystallization temperature the long period obtained from X-ray diffraction measurements at low angles varies in accordance with molecular weight and concentration, particularly in the range of low molecular weights. Density measurements showed that only for the highest molecular weight (ff/v= 150,000) is the density lower. A reduction in density is due to the presence of long loops. This is in agreement with the microphotographs obtained which show that the fraction of highest molecular weight does not give single crystals with well defined surface, as observed for all other fractions. Thus, these results support Keller's single crystals model in which in addition to steeply bending folds, there is a very small n u m b e r of long loops. I n Ituggins paper views were expressed explaining the causes of polymeric folded

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crystal formation. The basis of these views ist he fact that the arrangement of atoms forming the polymer molecule in the crystal is the result of both intermolecular and intramolecular interactions. Polymeric chain molecules (or molecular segments) can be packed into a regular (crystalline) structure at considerable distances in the direction of chain axis. However, as a result of gradual displacement of atoms or groups inside each molecule in relation to the surrounding molecules under the effect of intramoleeular forces of interaction from a certain critical limit, this structure becomes unstable. When this limit is achieved structural change can be expected. A variation in chain conformation with the formation of folds may be one such change. As an example Huggins proposed the following patterns for the formation of polyethylene single crystals: zigzag chains in linear polyethylene crystals are slightly twisted because of repulsion between the hydrogen atoms in the series of methylene groups on the same side of the molecule chain and these slightly twisted chains can be packed together without too strong intermolecular repulsion only at a certain distance in the direction of the chain axis. I n the paper b y V. Holland and P. Lindenmeyer (U.S.A.) a molecular theory was proposed which explains the formation of folds in polymer chains during crystallization from dilute solutions. According to this theory, the isolated polymer chain, greater by a certain critical value, can reduce its energy b y crystallizing in a regular conformation with folded chains. The molecule fully surrounded by other molecules in the crystal cannot reduce its energy in forming folds, as long as the molecule length does not exceed the critical thickness of the crystal. If all molecules are of the same length, the theory predicts the formation of a series of discrete metastable conditions dependent on crystallization temperature. For a polymer with a certain distribution of molecular lengths this series of discrete conditions can be replaced b y a continuous series u n t i l fractionation occurs during crystallization, as observed in the case when crystallization takes place at a lower rate, or from a dilute solution. A model of a folded polymer crystal was used in a n u m b e r of lectures given at the section. D. Hoffman (U.S.A.) proposed a simple theoretical examination for two stages observed during the isothermal growth of a lamella with a folded chain. At the first stage of crystallization the ends of c h a i n s - - " e i l i a " - - r e main projected beyond the limits of the crystal surface. At the second stage of crystal growth the "cilium" is drawn in the crystal surface. E. Fischer and D. Hinricksen (German Federal Republic) in their paper dealt with the analogies and differences in melting single crystals of polyethylene and stretched polyethylene. I t was shown b y I)TA t h a t in the case of a single crystal the melting point is displaced to higher temperatures after annealing and this corresponds to a growth in the dimensions of crystals earlier observed by X-ray diffraction at low angles. For a stretched specimen no marked displacement was observed in the melting point on annealing and there is no relation between the melting point a n d the long period. These and other observations are explained on the basis of a stretched polymer model, according to which most polymer chains are incorporated in different crystallites. R. Hoseman and V. Wilke (German Federal Republic) in their paper on paracrystallinity in linear high polymers noted that a significant feature of chain molecules is the ability to form folds on the boundary of paracrystalline grains contained in the socalled crystalline phase of polymers. The completely irregular chain segments are concentrated in the amorphous phase and at the grain boundaries. Japanese scientistis A. Nakadzhima, F. Khamada, S. Khaiyashi and T. Sumida reported data concerning the effect of solvents on the formation of single crystals from dilute solutions of polyethylene. They obtained experimental proof indicating that the surface irregularity of single crystals depends on the thermodynamic interaction between the polymer and solvent and on the molecular dimensions of the solvent. Results of electron-microscopic investigations of the effect of solvents on the molecular and supermolecular structures of polysaccharido derivatives and the influence of precipitants on the morphological structure of arnylose were reported in the paper b y G. Bittiger and E. Huzeman.

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Considerable interest is attached to the papers of B. Wunderlich and B. Prime and also T. ]:)avidson and B. Wunderlich (U.S.A.) dealing with polymer crystals with fully stretched chains. Crystals with stretched chains have now been obtained from polyethylene, polyoxymethylene, polycaprolactam and polytetrafiuorethylene. Thermodynamic and morphological investigations showed that these polymer crystals are nearest to equilibrium. Therefore it became possible to discuss the problem of equilibrium melting of polymers on the basis of experimental data. I n the first paper theoretical and experimental characteristics are given for melting polyethylene crystals with stretched chains with a wide molecular weight distribution. The second paper reports the special cell developed by the authors for differential thermal analysis during crystallization and melting polymer at high pressures and temperatures. I n this cell under these conditions, ethylene-propyleno and e t h y l e n e - b u t - l - e n e copolymers were crystallized. Japanese scientists, K. Takamitsava and T. Oiyama studied b y DTA the effect of molecular weight on melting of polyethylene. For high-molecular weight fractions of polyethylene on increasing crystallization time the peak on the thermogram, corresponding to melting of the polymer, breaks down into a high-temperature and low-temperature one. The high-temperature peak relates to melting of crystallites, crystallizing at the temperature of crystallization, T x and the low-temperature peak to melting of less stable crystallites formed during quenching after crystallization during a given time. The dependence of m a x i m u m melting point, T m, on crystallization temperature, T~, differs for polyethylene fractions of high and low molecular weights. The authors explain this difference by the fact that when crystallization of low-temperaturs polyethylene is carried out at atmospheric pressure with low degrees of supercooling, crystallites with stretched chains are formed. For such crystallites the melting point is almost independent of crystallization temperature. I n the paper b y I. Mitsuishi and M. Ikeda (Japan) two exothermal peaks were reported (at 120 and 238 °) on the thermogram showing the crystallization of polyethylene terephthalate. Electron-microscopic studies showed t h a t crystallization at 120 ° takes place with the formation of fibrils, whereas during crystallization at 238 ° spherulites grow from sheaf-like fibrils. A. Odadzhima, T. Ueno and T. Meada (Japan) reported X-ray investigations of orthorhombic and monoclinic polyethylene crystals over a wide range of temperatures from -- 180 ° to 120°C. Based on this investigation it was assumed that the monoclinic form can be stable thermodynamically at very low temperatures. I n Vichterl's paper it is pointed out t h a t model compounds can be used to study: 1) reactivity, 2) mechanical properties and 3) structure of polymers. The most important problem to be solved b y model compounds is the interpretation of polymer structure. The chief methods of studying polymer structure are infrared spectroscopy (IRS) and ~MI~ spectra of high resolving power. The most important information on polymer structure, in Vichterl's view, is obtained by IRS and additional information gained by NMR. To illustrate this statement, Vichterl gave examples of the interpretation of the structure of polyvinyl chloride, polyvinyl alcohol and polyvinyl acetate. At the sectional meeting Czech scientists Shtokr, Shnaider, Kolinskii, Riska and Lira reported their method of determining the tacticity of polyvinyl chloride (PVC) b y IRS. When determining the degree of tacticity by this method of PVC specimens obtained in the temperature range of ~- 50 to -- 50 ° it appeared that the tacticity of various specimens differs b y a m a x i m u m of 4%. The slight difference in the tacticity of specimens produced over a wide range of temperature, together with the considerable difference in physical properties, e.g. in solubility, point to the fact that tacticity is not the sole factor determining physical properties. As is well known, solubility depends on the content of anomalous structures. Consequently, the amount of these anomalous structures should be more sensitive to variations in polymerization conditions. I n the paper by Japanese scientists Sager, Matsur, and Miatsav, from an investigation of IRS of low-molecular weight model compounds and their analysis in relation to the

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spectra of corresponding high-molecular weight polymers of polyoxymethylene (POM) and polyethylene glycol (PEG), it was shown that the molecular conformation of P E G varies markedly from the helical to random convolution during melting of the polymer, whereas POM hardly becomes disordered on melting. Consequently, the fusion entropy of P E G is higher and it can be expected that its melting point is lower. I n fact, the melting point of P E G is 66 ° n a d of POM 178 °. Such a difference between the melting points of these two polymers can be partly due to their molecular conformation in the liquid state. Czech scientists Doskochilova, Sikora, Pivkov, Oberainger and Lira also reported the results of a study of the molecular structure and I~MI~ spectra of polymethylacrylate models, which is part of a systematic investigation of the conformation of model compounds of vinyl polymers. The use of high resolution I~MR techniques made it possible to study the microstructures of solutions of such polyelectrolytes as polyethylene-imine and obtain detailed information on the structural variations of polyelectrolyte segments in charged, uncharged and coordination states. This study was reported in the paper by Kang-DzhenL ' y u (U.S.A.). Three papers were devoted to the study of free radicals in irradiated polymers by means of E P R spectra. I n the paper of M. Ivasaki and K. Toriiama (Japan) free radicals and their variation under the effect of ultraviolet light in a ~,-irradiated copolymer of tetrafluorethylene and hexafiuorpropylene were investigated. I t was found that on irradiating this copolymer three types of radical - - C F 2 - - C F - CF2-- (Ri), ~ CF2-- CF2-- O'(R2) and ~ CF 2 - C'(CF3) CF~ ~ (1~3) are formed. Generally speaking, radical R3 should be more stable t h a n radical R1. However, in the copolymer it appeared that radical R3 is less stable thermally than radical R1. The authors explain this by the fact t h a t a large part of the 1~8 radicals is in the amorphous part, as the groups of CF3 hinder regular crystallization of the polymer chain. Under the effect of ultraviolet light at 77°K the shape of the E P R singal changes, which the authors explain by the conversion of radical R3: -

-

-

CF~

I

-

CF~

ho

I

~ ~ C F 2 - - C - - C F ~ ~ ~ ~:~ ~ ~ C F 2 - - C F - - C F 2 ~ ~ Radical R4 is thermally converted to radical Rs. The effect of steric conformation of radicals on the hyperfine structure in E P R spectra was pointed out in Kusumoto's (Japan) paper, which dealt with the study of E P R spectra of polypropylene with a varying stereospecifie nature. The effect of polymer chain conformation on the EPI% spectrum of irradiated high polymers was also studied in the paper of Kashivabara, Soma and l~ara (Japan) using the example of polyethylene (PE) and isotactic polypropylene (IPP). I t was shown that, on heating I P P irradiated at 77°K to room temperature, an intensive loss of alkyl radicals occurs at two temperatures near 170°K and 262°K, i.e., at temperatures corresponding to defrosting of molecular motion in PP. By the subtraction of spectra obtained at corresponding temperatures, free radical spectra were obtained which disappear at temperatures of 170 and 262°K and the possible steric configuration of polymer chains surrounding these free radicals was calculated. I n Okada and Mendel'kern's paper (U.S.A.) results are reported of an investigation into the irradiation of polyethylene (PE) in the completely molten state. Data previously obtained were confirmed, according to which the effectiveness of cross-linking P E in the molten state is twice as high for a highly crystalline specimens as for amorphous PE. Below 100 ° the effectiveness of cross-linking becomes comparable for these specimens. I t is very important t h a t during irradiation in the molten state with a low dose, the radiation yield of hydrogen, G(H~) markedly depends on the average molecular weight; G(H2) increases

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eta/.

with higher MI~. There is a very close correlation betwene G(H~) and the loss of terminal double bonds, i.e. the vinyl groups are traps for hydrogen atoms. This is the cause of the dependence of G(H2) on M N. At the section "Physical Properties of Solid Polymers, Melts and Concentrated Polymer Solutions" over 80 papers were read. Some papers were reviews and contained information which had been published in the literature between 1964 and 1966. Sectional papers were divided into subsections: high-elasticity, visco-elastic and dielectric properties, molecular motion, mechanical properties, physical properties of polymer mixtures, glass-transition, thermal conductivity, electrical properties, diffusion and surface effects, rheological propreties of melts and concentrated polymer solutions. Allen, Gee, Kircheim, Price and Paget (Great Britain) studied the thermo-elastic properties of b u t y l rubber within the elongation range of 1.05--2.0. Values of (Of/0T)L, V were determined b y both direct and indirect methods. I t was found that the agreement of data obtained b y these two methods is less satisfactory for butyl rubber t h a n for natural rubber, which is explained b y the relatively higher energetic effect of the latter. For b u t y l rubber an increase is observed in the internal energy during elongation at constant volume. The data obtained qualitatively prove the Flory theory for a Gaussian chain network, the distance between the ends depending on temperature. G. Mark and Flory (U.S.A.) studied elongation isotherms of polydimethylsiloxane with a varying degree of cross-linking during expansion in a solvent, in order to determine the constants in the Muni-Rivlin equation under conditions as near to equilibrium as possible. Unlike earlier studies, they did not reveal hysteresis effects, which is due to the satisfactory approximation to equilibrium conditions. I t was found that the coefficient C2 of this equation depends on the network characteristics. The authors came to the conclusion that this coefficient can be used to calculate the temperature coefficient of the dimensions of the undisturbed polymer chain. K. l~agai and T. Isikava (Japan) calculated the photoelastic coefficients for polydimethylsiloxane using the Flory-Creshendi-Mark model and compared the data obtained with Tsvetkov and Grishchenko's experimental data. I t was found that the data agree only if the conformation parameters adopted for the calculation markedly differ from the parameters used in Flory's study. The experimental dependence of the physical properties of polyurethanes of various compositions on structure was studied b y T. Tanaka and T. Iokoyama (Japan). Such structural factors were investigated as chemical chain structure, lateral methyl groups, type of cross-linking agent, polar groups. All these factors have a strong effect on the physical properties of polymers, including high-elastic behaviour. Kh. Yanai (Japan) studied the high-elastic properties of crystallizing and non-crystallizing elastometers in swollen and non-swollen states. I t was found that unlike non-crystallizing elastomers, the crystallizing types show increased stress on swelling in the stretched state which is due to crystallization and melting under the effect of stress and solvent. The effects observed are qualitatively explained by the swollen network theory, b u t quantitative analysis has so far been impracticable. I n the paper by T. Oiama, K. Ire, M. Nisumura and M. One (Japan) a description is given of a new device for the simple and rapid determination of the temperature dependence of viseo-elastie properties. I n point of fact, the device takes the form of dynamometric scales, in which the sphere is the indenter. The device is fully automatic in operation: loading and the change of temperature are effected according to a given programme, the curves are recorded on a diagram tape. An interesting feature of the device is the place where the sphere enters the polymer and which automatically changes from cycle to cycle. T. K h a t a and 1~. Yamaguchi (Japan) studied relaxation effects in polyethylene

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tercphthalate b y measuring the dielectric loss factor over a wide range of temperatures. They pointed out that according to the theory, a temperature time superposition can be established. At high temperatures a second absorption peak was found, the position of which depends on the degree of erystallinity. T. Ueko, K. ,M.urakama, T. Kusano and S. T a m u r a (Japan) investigated stress relaxation in heterogeneous polymer systems: polymer mixtures a n d block copolymers. For all these cases the distribution of relaxation time was determined. For the block-copolymer of styrene with butadiene two ranges were found. I n some respects this copolymer behaves as a mechanical mixture. I n the second half of the paper the authors sought to derive an equation to determine the chemical rheological behaviour of the polymer from the point of view of the location of rupture: in the main chain or in the cross-link. I n E. Yana5ek's paper (Czechoslovakia) low-temperature mechanical dispersion was described in polymers with polar groups (acrylates) swollen in different solvents. I n the case of polyethylene glycolmethacrylato two types of dispersion maxima were found, one of which depends on the nature and concentration of the solvent while the other is independent of these factors. Two papers read b y G. Peterson and B. R e n b y (Sweden) reported results of dynamic mechanical investigation of polyvinylchloride and chlorinated polyvinylchloride. I n the first case transition ranges were found which correspond to the glass-transition temperature and a secondary transition at --55 °. Activation energies were derived for segment motion and for group vibrations along the chain. For chlorinated polyvinylchloride the transition range corresponding to glass-transition is displaced in the direction of higher temperature and the secondary m a x i m u m is at --35 °. The position of these transitions depends on the chlorine content. A. l~isioka and I. K a t e (Japan) investigated dielectric losses in polypropylene and poly-4-methylpent-1-ene. I t was found that the dielectric losses are mainly determined b y a slight dipole moment of the methyl groups. For polymethylpentene the m a x i m u m loss was at 50 ° and an abnormally sudden reduction of losses occurs above this temperature which, according to the authors, was due to structural changes in the crystalline phases. I n the papers b y N. Koipumi, S. Yano and F. Tsui (Japan) the dielectric properties of polytetrafluoroothylene and a tetrafluorethylene-hexafluoropropylene copolymer were compared. I f the first polymer revealed the properties of a typical nonpolax substance, for the second a loss peak exists at 110 ° which is due to the slightly polar nature of the copolymer. J. Sibayama a n d M. Kodama (Japan) reported studies of crosslinked polymers obtained in the presence of a solvent causing swelling. Copolymcrs of divinylbenzene, ethylene glycolmethacrylate, methyl methacrylate and styrene were studied in different ratios. I t was found t h a t the characteristic parameters of the visco-elastic behav. iour of eopolymers depend on the history of the specimen: conditions of eliminating the solvent, repeated swelling, etc. The authors explain the results obtained by network topology, reflecting the variations in the m u t u a l position of chains after various treatments. R. Kerns, R. Ralston and E. Vanderbery (U.S.A.) reported studies of the properties of epichlorohydrin elastomers (both homopolymer and copolymer with ethylene oxide), which have excellent dynamic mechanical properties. Data were cited in the report of the tangent of mechanical losses of these elastomers with various fillers. I t was found that for these polymers the Mullins effect is observed during elongation. The Mullins effect is due to the variations in the polymer phase. The increased flexibility of elastomers of this type is attributed b y the authors to the presence of oxygen atoms in the main chain. The authors correlate the presence of oxygen atoms in the polymer chain with relatively considerable lack of ordering of the elastomer in the relaxed state, which accounts for the considerable entropy variation during relaxation from the stretched state. These properties favourably distinguish this class of elastomers from elastomers with only carbon chains.

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Several papers are devoted to the s t u d y of molecular motion in polymers. I n S. Sobadzhima's (Japan) paper the proton magnetic resonance method was used for the s t u d y of concentrated poly-7-benzyl-L-gntamate solutions in the liquid-crystalline state. The film formed from liquid crystals in a magnetic field revealed an oriented texture during the X - r a y investigation. K. Y a m a g a t a and T. Tsuchiya (Japan) calculated the second moment of the absorption band for stretched polytetrafluoroethylene based on the assumption t h a t aU the molecular chains rotate round the axis of the main chain. The calculated values agree with experimental data, which proved the r o t a r y nature of transition in this polymer at room temperature. S. Ivayanagi, Kh. Nakane and I. Sakurai (Japan) investigated the structure and molecular motion in trans-l,4-polybutadiene. They found t h a t contrary to N a t t a ' s data, this polymer belongs to the monoclinic system. During phase transition it changes into the hexagonal system. This feature has so far remained unexplicable. F o r polytetrafluoroethylene a m a r k e d reduction was observed in the retardation time in the direct proximity to the phase transition temperatures. K. Khikisi. A, Chiba and L. Furuichi (Japan), studying polyoxmethylene and polyoxyethylene b y nuclear magnetic resonance, came to the conclusion t h a t the molecules perform either r o t a r y or oscillatory motion in the crystalline regions. The angular dependence of line width was studied a¢~ different temperatures and the results established the oscillatory model of motion, which is also supported b y results of X - r a y analysis. "When investigating polymethylene b y NMR and b y dynamic and mechanical methods, S. Matsuoka, I. Isida and K. Aloizio (U.S.A.) found t h a t crystal morphology dependent on crystallization conditions influences the nature of mechanical losses. I f the polymer crystallizes in bulk, it is characterized b y a large low-temperature peak a t --110% I f polymer morphology is characterized b y stretched polymer chains, the relative heights of peaks are reversed. Henee, the authors eonelude t h a t the first peak is related to the motion of interlamellar regions and the second to defect motion in the crystals. T. Khidesima (Japan) investigated mechanical losses in polyethylene in the presenee of solvents. He revealed t h a t solvents displace the gl-peak in the direction of low temperatures and increase its intensity, whereas the a2-peak remains unchanged. I t follows from these results t h a t the first peak is v e r y closely related to the amorphous phase a n d the second to the crystalline phase. M. Takayanagi and T. Matsuo (Japan) used the dynamicmechanical m e t h o d to investigate the visco-elastic properties of monocrystals of polyethylene and trans.l,4-polybutadiene. T. Tatsumi (Japan) found for the first case t h a t four types of "crystalline absorption" exist for single crystals: a peak which is typical of annealed specimens; a peak typical of isothermally crystallized specimens and peaks due to structural variations in the specimens and to melting of crystals. I n the second case the effect of annealing was studied and it was found t h a t during annealing the conversion temperature of crystals alters b y a p p r o x i m a t e l y 15 ° due to simultaneous variation of crystal thickness. To elucidate this effect, the Keller model was used. The author considers t h a t this behaviour of crystals is caused b y the distribution of loops at the ends of folds. Several studies were made of the mechanical properties of oriented polymers, in order t o elucidate the properties of single crystals. I n the paper b y K. Nakamae, K. Kadzi and S. Vadano (Japan) the assumption was examined t h a t when determining the elasticity modulus stresses are evenly distributed in the length and width of the crystal. The s t u d y carried out on polyvinyl alcohol a n d polyethylene specimens of varying degrees of crystallinity and orientation confirmed this assumption, which provides a basis for calculating the elasticity modulus of single crystals. K. Isikava, K. Miyasaka and M. Maeda (Japan) investigated residual deformations in polyethylene crystals b y X - r a y diffractometry. I t was found t h a t the rate of deformation of the fibre depends on the residual deformation of crystals. K. K o b a y a s i and T. Nagasava (Japan) reported investigations of elastic recovery in polyethylene, stretched to varying degrees. After cyclic loading of specimens cut at dif-

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ferent angles in relation to the direction of stretching, structural variations were investigated by a diffractometric method, whereby certain lattice distortions were revealed as dependent on the angle at which the specimen is cut. The authors explain these distortions by bending of crystals which, in addition to interlamellar slip, is responsible for the peculiar elastic behaviour of the polymer. K. Kavai, T. Oda, S. ~ o m u r a and T. Khasimoto (Japan) investigated elastic recovery in polyvinyl alcohol and polyethylene specimens oriented to varying degrees. As well as investigating the elastic properties, birefringence, light scattering and X-ray diffraction were also studied. Crystal orientation was explained on the basis of spherulite deformations, the crystalline planes, which form the spherulite, being oriented units. A certain deformation takes place simultaneously with orientation. The structural changes in polyethylene terephthalate occurring during neck formation while stretching were investigated b y S. Isizaki and T. Kobayasi (Japan), As a result of the study critical rates of deformation were established for amorphous and crystalline polymers. I t is assumed that in an amorphous specimen the chains slip, while in a crystalline specimen the chains open and the crystallites rupture; in the latter case the amorphous chains are more rapidly oriented t h a n in a purely amorphous specimen. R. Kitamaru, Kh. Chu a n d V. Tsui (Japan) observed the crystallization of slightly cross-linked polyethylene in the stretched state. The nature of the kinetic curves cannot be explained b y any of the well known mechanisms of nucleation. I n every case the rate of oriented crystallization was higher t h a n the rate of isotropic crystallization. A group of papers devoted to optical methods of studying polymer deformation is of interest. S. Onogi, T. Asada and T. F u k u i (Japan) measured the variation of birefringence during stress relaxation for quenched and annealed polyethylene films. I t was found t h a t in a certain range of temperatures the principle of temperature-time superposition can be used. The shear factor for the mechanical properties is higher t h a n for optical ones, which indicates that the temperature dependence of mechanical a n d optical properties cannot be described b y the same mechanism of deformation. R. Yamada, K. Khayasi a n d S. Onosh (Japan) carried out simultaneous studies of the dynamic modulus and photo-elastic properties according to frequency for numerous polymers, and found that measurements of birefringence and dichroism combined with mechanical measurements produce new information on the deformation mechanism of polymers. T. Kavaguehi, T. Ire, Kh. K a v a i and R. Stein (Japan), using methods of X-ray diffractometry, determined the time of crystal orientation in polyethylene in a fairly wide frequency range of mechanical effects. For the orientation of axis 110 an activation energy of 45 keal/ /mole was found. Legran also used low-angle X-ray techniques for the study of the orientation of crystalline phases during stress relaxation. He found that the orientation of crystals occurs during a period of 0 - 1 - 5 see, after which no changes whatsoever occur. R. Gore, T. Takenaka, Dzh U m e m u r a a n d S. Khayasi developed a special method for the simultaneous measurement of stresses and infrared dichroism and used it for the investigation of relaxation in n a t u r a l rubber and polyethylene. I t was found that in rubber relaxation it is due to the orientation of the amorphous phase, while in polyethylene, to the orientation of the crystalline phase. Comparatively few pap.0rs investigated the mechanical properties of polymers. V. E n o a n d iYi. Isikava (Japan) studied the tear resistance of polymer films. They pointed out that the energy required for tearing the film is satisfactorily correlated with the surface energy. The tear energy in the direction perpendicular to the direction of orientation depends to a lesser extent on the degree of stretching the film t h a n in the parallel direction. The tear of films was also studied by S. Yamasita, T. Kotani and Dzh. F u r u k a v a (Japan), who pointed out that the tear resistance is not only related to the tensile strength of the film, b u t also to the moduls and the breaking elongation. S. Fukukhara, I. Suzuki and S. Omoto

1082

I. YA. PODDUBNYI e t a / .

(Japan) studied the strength and concentration of nylon 6. They found t h a t a reduction in the strength of nylon at increased temperature is due to the increased length of hydrogen bonds and reduced crystallinity. Higher concentration force is due to the same causes, a n d in addition to the decomposition of micro-crystallites and the entropy effect. The frictional properties of polyamides were investigated b y K. Matsubara, M. Vatanabe and K. Karasava (Japan), who found t h a t critical load depends on the slip rate and the product of load and rate is almost constant. I. Yamaguchi and S. Amano (Japan) attempted to investigate the relation between hardness and internal stress arising during the measurements. They came to the conclusion that hardness increases with higher compressive stress and decreases with higher tensile stress. I n Okamoto's paper the visco-elastic properties of low- and high-pressure polyethylene and mixtures were investigated b y a dynamic method. A comparison of experimental data with the theory based on a two-phase mechanical model appeared to be fully satisfactory. I t was also pointed out that the properties of a crystalline polymer mixture can be expressed by the properties of components and their volumetric proportions. S. Yamada, S. Sakadziri and It. Khirako (Japan) investigated the mixing of polymers of poor compatibility (polycarbonate and polyethylene). The properties of the mixture and the nature of phase dispersion was studied in accordance with the method and conditions of mixing. I t was found that melt viscosity of the mixture decreases in comparison with the viscosity of pure components. The specific impact viscosity of the mixture is higher t h a n t h a t of the pure components and passes through the maxi m u m at a polyethylene content of about 5%. I n the paper b y B. P. Shtarkman (U.S.S.R.) problems of structural variation in polyvinylchloride during processing were discussed. I t was pointed out t h a t the initial globular structure has a marked effect on processing of polymers with and without a plasticizer. S. Yamasita, Dzh. F u r u k a v a and T. Vatanabe (Japan) reported investigations of the structure and mechanical properties of vulcanized mixtures of various synthetic elastomers. They pointed out that the mechanical properties depend both on the degree of heterogeneity of the mixture and on the vulcanizer. Co-vulcanization was observed in m a n y systems. E. Ototska and F. Eirick (U.S.A.) studied the properties of copolymers of butadiene with acid and basic groups and the salts and mixtures of these copolymers. Polyelectrolyte rubbers of this type have a high glass-transition temperature and high elasticity modulus. Network density is also high because of the interaction between functional groups. The variations of properties with temperature are so sudden as a result of dissociation that the principle of temperature-time superposition for the glass-transition temperature appears to be incorrect. G. Allen, It. Aierst, Y. Cleveland and Ch. Price {U.S.A.) investigated the heat of solution of polystyrene vitrified under conventional conditions and under pressure. I n both cases the heats appeared to be similar, regardless of the fact t h a t specimen densities varied markedly. The results obtained have not so far, been explained by conventional glass transition theories. I. Uematsu and K. K h o n d a (Japan) proposed two equations to calculate the glass transition temperature of Copolymers of a n y type from the glass-transition temperatures of homopolymers which, unlike earlier equations, can take into account the presence of maxima, glass transition temperature being dependent on copolymcr composition. One of these is a modification of the Gordon-Taylor equation and the other, a modified version of the Gibbs-Dimartio equation. I n both cases the authors allowed for the effects of variation in volume and bond length. The equations derived can be used for stereospecific copolymers of various types. A. Shimazaki (Japan) investigated thermal expansion curves of epoxy resins of varying degrees of cross-linking. He found t h a t below and above the glass-transition temperature the dependences of specific volume on the degree of cross-linking are contradictory. This effect is explained b y the author from the point of view of theories of the free volume and natural volume of macromolecules. Glass-transition in epoxy resins was also investigated b y 1~. Site (Japan), who

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studied the effect of separate components of the system, concentration of the agent accelerating solidification, and process conditions. He explained the data obtained b y segment motion. I. Vada, I. K h o t t a and R. Suzuki (Japan) observed two glass-transition temperatures and two ranges of scattering in polypropylene and attributed them to two types of amorphous phase, one of which is rich in atactic chains and the other in isotactic chains. From these views they explained the variations in glass-transition temperature after annealing and ageing. V. Lotz, Yu. W h i t m a n and A. KovaSs (France) carried out dilatometric and structura 1 investigations of styrene and ethylene oxide block copolymers. Specimens with a varying component ratio have a glass-transition temperature corresponding to polystyrene and a melting point corresponding to polyethylene oxide. Up to a polystyrene content of 0.5 weight fractions the polymer morphology has a spherulitie nature; at higher polystyrene content spherulites were not observed. The special features of transitions the authors explained from the point of view of microphase theories, whereby a Keller folded model was used. F. Miiller (German Federal Republic) investigated the anisotropy of thermal conductivity and dependence on conditions of polymer stretching. The author came to the conclnsion that b y using these data a more detailed view can be established of the deformation mechanism of polymers and the network structure near the glass-transition temperature. S. Oka and K. Yamane (Japan) in their paper derived a ratio between the thermal conductivity of cellular plastics and the volume fraction of cells. Statistical models of cellular plastics with open and closed pores were studied. M. Iosephovich, L. Iou, D. Perichson, S. Dezai6r and R. Bouv~ (France) investigated the electrical properties of semiconductor polymers obtained b y the polycondensation of aniline. A study was made of the dependence of properties on polymer structure and polymerization conditions. The electrical properties of polyvinylpyrene were studied by Isizuka et al. I t was found that polyvinylpyrene is a photoconductor and the greatest effect was obtained on illuminating the positive electrode. A further study was made of the dark current and the dependence of all characteristics on the wave length of incident light. M. Krizhevskii, A. Shimanskii and Yu. Piotrovskii (Poland) investigated the conductivity of polyethylene, polyvinylchloride and polyvinyffiuoride and revealed two types of conductivity. I n v a c u o and in inert gases n-type conductivity is produced by discharge carriers which pass through the polymer volume from the metallic electrodes. This conductivity increases during illumination and shows a strong polarization. Oxygen reduces these effects. The second type of conductivity is revealed on saturating the specimens with water, it is ionic and a negative photoeffect is observed. R. Ross (U.S.A.) measured the surface tension of several molten polymers b y the suspended drop method. I n K. Tsuda's paper (Japan) a study was made of the diffusion of dyes in polymer fibres which had been stretched to varying degrees. The coefficient of diffusion in the longitudinal direction appeared to be much higher than in the transverse direction. The ratio of diffusion coefficients in the longitudinal and transverse directions appeared to be dependent on the molecular shape of the penetrant, whereby for ellipsoid molecules it is higher t h a n for spherical ones. The diffusion of dioctyl phthalate into extruded polyvinylehloride was investigated by S. Oikava, A Simazaki and T. Sakura (Japan). The distribution measured showed a deviation from the second Fick law. I t was found that the rate of diffusion depends on the density of the extruded specimen. U. Buss (U.S.A.) proposed an explanation of certain viscosity effects on the basis of the mural contact of molecules. I n his view high polymer viscosity in the melt involves large energy losses when there is a slip in the contact. At high rates of shear these contacts cause the formation of molecular globules which rotate as a whole, causing elastic turbulence. These causses, in the author's view, explain the roughness of the extruded material and the formation of gel-like particles when mixing the solutions. S. Onisi and S. Ire (Japan)

1084

I. YA. PODDUBN¥I et al.

studied the adsorption of various organic compounds and water by fibres, on the surface of which polystyrene had been grafted. I t appeared that such graft fibres can be useful for the recovery of these substances in small quantities from the solutions since adsorption takes place without deformation and rupture of fibres. K. Megiro, M. Ueno and K. Yamaguehi (Japan) studied the surface pressure isotherms of films of partially or wholly substituted polyvinylbenzals in water. I t was found that the m a x i m u m area for partially substituted polymers is larger t h a n for fully substituted polymers. A reduction in area is explained by the immersion of the hydrophilie part of polymer molecules in the aqueous phase and b y the formation of a contracting film. I n salt solutions the limiting area of partially substituted polymers increases, which is explained b y the salting out of hydrophilie components of maeromolecules from the aqueous phase. I. Aoki (Japan) studied adhesion between isotactic polypropylene and chlorinated polypropylene. He found that the bond strength of these two polymers is influenced by conditions of chlorination of polypropylene, isotacticity before chlorination, chlorine content a n d doubling conditions. As all these factors are due to crystallinity, the author attempts to explain the adhesion properties of these polymers from this point of view. Problems of adhesion were also discussed in K. Nakao's (Japan) paper. Assuming t h a t the cohesive strength is proportional to tensile strength and adhesive strength to fluidity, he tried to find a corresponding expression for the resistance to separation. For the dependence of resistance to separation on layer thickness he found a fairly simple expression. The paper generalized some data on the adhesion of sulphonated polyethylene to metallic surfaces. O. Inagaki, S. Khirose, T. Sacki and S. Okamura (Japan) reported certain properties of synthetic paper based on polyvinylalcohol fibre and vinylone. On processing the mixture in conventional paper-producing machines, polyvinylalcohol fibres swell and ensure a good adhesion bond. S. Onogi, T. Masuda a n d N. Miyanaga (Japan) proposed an expression to determine the relation between the molecular weight of the polymer a n d the concentration of the polymer solution at constant viscosity: c . M ~ / ~ c o u s t . The value of fl/g for a given polymer-solvent system is independent of molecular weight and concentration and is only related to molecular dimensions in solution. The relation between molecular weight and melt viscosity was discussed in S. Imai's (Japan) paper. The discussion followed the point of view of molecular interaction between the maeromolecules without a n y reference to views on "contacts". From the discussions it follows, in particular, t h a t a t high molecular weights log ~~M½. S. Sisida (Japan) proposed a semi-empirical equation for S-shaped curves of polymer fluidity based on the assumption that viscosity is related to macromolecular viscosity in shear. The parameters of the equation can be easily calculated from experimental data. I t was pointed out that one of the parameters related to macromoleeular deformation, should be equivalent to the inlet correction during flow in the capillary. This assumption was experimentally investigated" a n d showed satisfactory agreement. K. Arakava and N. Takenaka (Japan) investigated the relaxation properties of aqueous polyethylene glycol solutions at ultrasonic frequencies and calculated the activation energy from the temperature relations of relaxation maxima. The absorption of ultrasonic vibrations in various polymer solutions was also studied b y Mikyahkara and Nomura: they derived a relation between the absorption coefficients and solution concentration. S. Nakamura and A. Tobol'skii (Japan, U.S.A.) carried out an extensive study of the viscoelastic properties of amylose, plasticized with dimethyl-sulphoxide. The investigations were made with a very wide range of plasticizer concentrations and it was found that with high amylose concentrations it exists as erystallites immersed in a plasticized medium and at low concentrations it homogeneously dissolves in the plasticizer. By extrapolation of data on the concentration dependence of glass-transition temperature, a glass-transition temperature was obtained for pure amylose at about 320 °. S. Kuroiva and M. Nakamura (Japan) proposed a description of the relaxation mechanism for Newtonian flow using

Problems of the chemistry and physico-ehemistry of polyurethanes

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a model which consists of several visco-elastic groups, each of them composed of m a n y Maxwell elements. Newtonian viscosity and the relaxation times were calculated for this model using X-operation according to Tobolskii. A satisfactory agreement was obtained with experimental data. T. Minesita, T. Vata~abe and S. Ono (Japan) investigated the flow of polyvinyl pyrrolidone solutions of different concentrations through capillaries. I t was found that viscosity depends to a great extent on capillary diameter. A reduction of viscosity on increasing capillary diameter was explained b y the liquid layer of a thickness of 10-4-10 -3 cm on the walls of the capillary as a result of steric hidrances in the heat motion of polymer molecules caused by pressure. T. Arai, I. Suzuki and N. Akino investigated pressure distribution along the axis of the mouthpiece for obtaining tubes on the screw type extruding machine. These measurements somewhat clarify the physical meaning of correction coefficients for the steady flow of visco-elastic liquid in the a n n u l a r capillary. I n addition, these data make it possible to conduct a more detailed study of the case of the Barus effect. I t is difficult to generalize from the above mentioned brief annotations of papers read at the 8th Section of the Symposium, as the subjects were extremely varied. This fact, in itself, proved to some extent the great interest in the study of physical and physico-chemical properties of polymers and polymer systems. I t is important to note that not only new methods, b u t chiefly new combined methods, are being used to study the properties of polymers. I n this respect a combination of mechanical and structural methods is of particular interest, which as mentioned was fairly widely used b y m a n y lecturers. Attention is given to the fact that a considerable proportion of the papers at the symposium came from Japanese authors. This was not only due to the location of the symposium b u t also to the extensive development of research in the field of polymers in Japan. All the papers were of high scientific level and were actively discussed b y those taking part in the symposium. Translated by E. SEMER~.

PROBLEMS OF THE CHEMISTRY AND PHYSICO-CHEMISTRY OF POLYURETHANES* YU. S. LIPATOV An~O~G a large number of polymers and polymeric materials known at present polyurethanes occupy a special place both in the variety of their practical application in the national economy and in the n u m b e r of specific properties. This explains the great interest in problems of chemistry, physieo-ehemistry and technology of polyurethanes both abroad and in our country. The scientific technical conference on the chemistry and physico-chemistry of polyurethanes, which was held in Kiev from the 10th to 13th October 1966, was devoted to the detailed discussion of the problem of polyurethanes, analysis of studies made and determination of the prospects of further investigations. The conference was organized b y * Vysokomol. soyed. A9: No. 4, 968-969, 1967.