bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light‐scattering measurements on viscose solutions
Authors: Onyon P. F. 
Published: April 2003

AbstractAn exploratory study has been made of the application of light‐scattering measurements to viscose solutions. The effect of aging on molecular weight and second virial coefficient has been investigated for two types of viscose differing only in degree of initial xanthation. By controlled filtration procedures prior to measurement it is possible to obtion information on the upper range of particle size distribution; in this way the presence of a small fraction of material of very high molecular weight has been demonstrated in the viscoses examined. This finding is in accord with results obtained by previous workers using other techniques.
G‐F transformation of actin as a fibrous condensation
Authors: Oosawa Fumio , Asakura Sho , Hotta Ken , Imai Nobuhisa , Ooi Tatsuo 
Published: April 2003

AbstractThe physical feature of the G‐F transformation of action caused by a small amount of magnesium ions was investigated by measuring flow birefringence, light scattering, viscosity, and sedimentation of action solutions at various concentrations of actin and magnesium ions. All experimental results indicate that the G‐F transformation of actin can be regarded as a reversible fibrous condensation. When the concentration of actin is increased at a constant concentration of magnesium ions, fibrous aggregates of actin molecules, F‐actins, can be formed only above a critical actin concentration which is determined by the condition of medium and decreases rapidly with increasing concentration of magnesium ions. Above the critical concentration, all of the excess active actin molecules are transformed into F‐actins. These F‐actins are coexisting with active (G‐)actin molecules, the concentration of which is independent of the concentration of F‐actin and equal to the concentration of active actin at the critical point. The state of apparent units of F‐actins in solution is also determined by the condition of medium and independent of the concentration. With increasing concentration of magnesium ions, the apparent units of F‐actin become longer and longer and their thickness increases. Small globular aggregates are always observed below the critical point of formation of long fibrous aggregates. These experimental results show qualitative agreement with theoretical results obtained by one of the authors on fibrous and globular aggregations of charged macromolecules.
A novel catalytic polymerization of olefins. Part II. High polymerization of ethylene by Al‐TiCl4 catalyst
Authors: Fukui Kenichi , Kagiya Tsutomu , Yagi Tetsuya , Shimidzu Takeo , Yuasa Sachio 
Published: April 2003

AbstractA novel high polymerization of ethylene by Al‐TiCl4 catalyst is studied. The polymer yield increases with higher TiCl4 concentration and with larger amount of Al metal used. With an Al/TiCl4 mole ratio larger than 10, the conversion slightly decreases. The highest conversion is gained at 180°C., and higher reaction temperatures decrease remarkably the yield of solid polymer. The molecular wight of polymers increases with the Al/TiCl4 ratio, but it remains constant at Al/TiCl4 ratios larger than 3. It is highest at 180°C. With respect to the Al/TiCl4 mole ratio, the melting point has a relation similar to that of the molecular weight. It is also maximum at 180°C. The rate equation is determined by some kinetic studies, obtaining the formula ‐dP/dt = 4.37 [TiCl4] exp{‐4800/RT}P for a certain range of reaction conditions. A possible cationic mechanism for this polymerization is suggested.
Colligative properties of polyelectrolyte solutions. V. Activity coefficients of counter‐ and by‐ions
Authors: Nagasawa Mitsuru , Izumi Mikio , Kagawa Ikumi 
Published: April 2003

AbstractSimultaneous measurements of the activity coefficients of counter‐ and by‐ions in polyelectrolyte solutions were carried out. Sodium polyvinyl alcohol sulfate was used as the sample of polyelectrolyte and sodium chloride as the extraneous salt. The activity coefficient of sodium counter‐ion was determined by using a sodium amalgam electrode and that of chloride ion was determined by a sliver‐silver chloride elctrode. It was found that the activity coefficient of both counter‐ and by‐ions has little relationship with the volume of polymer coil, and that the additivity of counter‐ion activity found for hydrogen ion by Mock and Marshall holds also for sodium ion. It was also found that there is good agreement between the experimental results and the theory of Katchalsky and Lifson if we use their same theory for calculating the volume of polymer coil, although the volume is too large to be considered reasonable.
Gamma irradiation of polymers of arly and alkary methacrylates and acrylates
Authors: Graham Roger K. 
Published: April 2003

AbstractPoly(benzyl methacrylate) and poly(phenyl methacrylate) appear to degrade exclusively on gamma irradiation; energies for main‐chain, carbon‐carbon bond breaking are 711 and 228 e.v., respectively, which indicates a strong protective effect of the benzene ring. Poly(phenyl acrylate) requires higher doses to cause gelation than do poly(benzyl acrylate) and poly(phenylethyl acrylate), the latter behaving similarly to poly(n‐alkyl acrylates). Absence of hydrogen on the carbon adjacent to the ester link appears to be required to affect the radiation behavior of polyacrylates.
On the coagulation of polymer latices by freezing and thawing
Authors: Barb W. G. , Mikucki W. 
Published: April 2003

AbstractThe particle size characteristics of coagulates obtained by freezing and thawing emulsions of polymers which are hard and glassy at normal temperatures, particularly polystyrene and styrene copolymers, have been studied. It is shown that for a given polymer the particle size distribution is principally determined by the macrostructure of the frozen mass, such as the size of the ice crystals formed and the concentration of polymer in the initial emulsion. The effect of chemical structure of the polymer on the freezethaw coagulation process is discussed and from the results it is suggested that the usual concept of a second‐order (glass) transition is not applicable to very fine latex particles of rigid polymers. This may also explain the formation of continuous films from fine latices at temperatures below the transition temperature of the bulk polymer.
Copolymerization of styrene with vinyl acetate and methyl methacrylate
Authors: Suzuki Momotaro , Miyama Hajime , Fujimoto Shiro 
Published: April 2003

AbstractBy the thermistor method, we measured rates of copolymerization of St(styrene)‐VA(viny1 acetate) and MM(methy1 methacrylate)‐St for various mixing ratios of the two monomers. In the St‐VA system, the large difference between the reactivity ratios of the two monomers causes a large error limit in values of 4, so that we could not find any essential regularities in the variation of 4 with successive mixing ratios. In the MM‐St system, however, where the difference of the two reactivity ratios is not so large, we can determine the values of 4 more precisely and obtain a concrete confirmation of Arlman's theory. As a result, we conclude that, for the MM‐St system (at. 24°C.), the termination constants for mixed radicals are larger than those for homogeneous radicals, and, furthermore, that the rate constant for a normal cross‐termination reaction is about 3 times larger than that of the cross‐termination reaction having a penultimate unit.
The effect of catalyst composition and structure upon the polymerization of butadiene and styrene by organosodium reagents
Authors: Morton Avery A. , Taylor Lloyd D. 
Published: April 2003

AbstractThe polymerizations of butadiene and of styrene by various organosodium reagents combined with sodium isopropoxide (or methylphenyl carboxide) and sodium chloride have been compared. In general a reagent which is a good promoter of 1,4‐polymerization of butadiene is a poor agent for isotactic polymerization of styrene and vice versa. Also, rapid polymerization of styrene seems unrelated to stereospecific polymerization of styrene. m‐Xylylsodium, combined with sodium isopropoxide and sodium chloride, was a preferred agent for isotactic polymerization of styrene but did not induce enough 1,4‐polymerization of butadiene to qualify as an alfin catalyst. Catalysts of this type might be called “albyl” systems in order to differentiate them from alfin catalysts. A definite relationship exists between the structure of the reagent and the polymer it produces. Therefore, adsorption of the monomer on the surface of the catalyst is probably the controlling and most important factor in polymerization induced by these reagents.
Low pressure polyethylene catalysts
Authors: Roha M. , Kreider L. C. , Frederick M. R. , Beears W. L. 
Published: April 2003

AbstractMost of the reported polymerizations of ethylene at atmospheric pressures utilize heterogeneous catalysts. This paper summarizes some studies of the polymerization of ethylene at atmospheric pressure with nonprecipitate titanium+4 catalyst systems. The nature of the alkyl metal used to make the catalyst influences the occurrence of reduction of titanium which produces the usual heterogeneous state. The highly active alkyl metals must be modified to decrease their reducing power. Electrophilic materials which are normally produced during the reduction step in the Ziegler catalysts must be present to obtain optimum activity of the nonprecipitate catalyst. The homogeneous titanium+4 catalysts described here are more active than the usual heterogeneous Ziegler catalyst. The catalyst formation is explained as due to the formation of complexes.
Crystalline poly(tert‐butyl acrylate)
Authors: Miller M. L. , Rauhut C. E. 
Published: April 2003

AbstractCrystalline poly(tert‐butyl acrylate) was prepared with lithium dispersions, n‐butyllithium, and lithium plus n‐butyllithium as catalysts. Methyl acrylate, n‐, see‐, and iso‐butyl acrylate gave only amorphous polymer under the conditions that produced crystalline poly(iert‐butyl acrylate). Very pure monomer was necessary for the preparation of crystalline poly(tert‐butyl acrylate) with lithium dispersions. That the poly(tert‐butyl acrylate) was crystalline was shown by x‐ray diffraction, observation with the polarizing microscope (preparation of birefringent spherulites) and the electron microscope, study of infrared absorption, softening point, and density, and finally by preparation of crystalline polymethyl acrylate from crystalline poly(tert‐butyl acrylate) by ester interchange. The nuclear magnetic resonance spectrum of the crystalline poly(tert‐butyl acrylate) showed no evidence of band splitting and the viscosity‐slope constant, k′, was the same for crystallizable and noncrystallizable polymer.
Promoted molybdena‐alumina catalysts in ethylene polymerization: Kinetic considerations
Authors: Friedlander H. N. 
Published: April 2003

AbstractPreformed transition‐metal oxides on high‐surface supports and precipitated catalysts from transition‐metal salts and aluminum alkyls produce linear polyethylene and stereoregular polyolefins. An introductory study of the kinetics of ethylene polymerization with a specially prepared preformed solid catalyst was undertaken as an aid in understanding the catalytic action. At constant pressure, ethylene uptake is linear. The rate depends on amount of catalyst and on ethylene concentration at various temperatures and pressures. The molecular weight of the product is primarily a function of temperature. The observed rate and its dependence on ethylene concentration and temperature are consistent with bound‐ion‐radical polymerization in a chemisorbed ethylene layer. The equations are similar in form to those based on a coordinate‐anion Polymerization mechanism. Further study will be needed to distinguish between these mechanisms, because they differ essentially only in the electronic environment of the growing chain end and in the movement of the growing reaction center during polymerization.
Crystallization kinetics of isotactic polypropylene
Authors: Griffith J. H. , Rånby B. G. 
Published: April 2003

AbstractCrystallization kinetics of Hercules polypropylenes were studied between 133 and 155°C. using dilatometers. The crystallization rates of these samples became too rapid below 133°C. for accurate dilatometric measurements. One sample (A) was a commercial sample containing stabilizer and 9% extractable polymer (with boiling n‐heptane). B was an experimental extracted sample containing no stabilizer. A portion of B was thermally degraded under vacuum at 350°C. for 7 hr. (C). The DPn′s of A, B, and C were 2300, 7300, and 1200, respectively. Their melting points were determined dilatometrically, under conditions approaching equilibrium, and were 175, 176, and 173°C., respectively. 95% of the crystallization can be described by an Avramitype equation with an n value of 3, indicating a three‐dimensional growth with residual nucleation or a two‐dimensional growth with spontaneous nucleation. The heterogeneities may result from catalyst residues. The crystallization rate of A was lower than that of B or C at a given temperature, possibly due to the presence of atactic polymer. At a given temperature C crystallized faster than B, which may be an effect of the difference in molecular weight. Plotting the rate as a function of the degree of undercooling (ΔT) increases the difference between B and C.
Anisotropic light scattering by flowing flexible macromolecules
Authors: Nakagaki Masayuki , Heller Wilfried 
Published: April 2003

AbstractThe dityndallism (anisotropic light scattering upon orientation or deformation of molecules or particles) to be expected from flexible macromolecules deformed in laminar flow is calculated for all angles of observation of practical interest. The model used is based on the assumption that the deformed molecule can be approximated by a statistical spheroid. The hydrodynamic part of the theory is based upon a treatment already published, while the optical part of the theory is based upon Rayleigh's treatment of spheroids, considering in addition its unpublished recent extension by Stevenson. Numerical evaluation of the equations arrived at lead to the expectation that dityndallism can give quantitative information on the shape of flexible macromolecules whose degree of swelling is known, or on the degree or swelling of macromolecules whose statistical shape is known.
Probability model theory of chain‐end activated polymer degradation. II. Second‐order radical termination
Authors: Gordon Manfred , Shenton L. R. 
Published: April 2003

AbstractNew analytical solutions are obtained for the kinetics of degradation when activation affects only the chain ends, and all chain ends have equal reactivity, using the following improvements in the models used. The initial polymer chains are distributed in size, following the radical‐combination type of distribution function (self‐convoluted exponential), rather than the chains being of equal size (homodisperse). The radical termination reaction is taken either kinetically of first order or second order. The latter case has not previously been solved exactly, because in the previous schemes of derivation it renders the differential equations nonlinear. Not unexpectedly, the results on the rates of decay of weight or molecular weight are very similar for first‐order and second‐order radical termination. The improvements in the model undoubtedly make these calculations more realistic than those previously available, but the results do not at all improve the fit of existing data on the rate of decay of the mean chain length with conversion in the degradation of polymethyl methacrylate. Probably this happens because the results are sensitive to the incursion of minor side reactions not yet taken into account.
Interpolyesters containing pinic and homopinic acids
Authors: Wielicki Edward A. , Boone Charles J. , Evans Robert D. , Lytton Marion R. , Summers Hugh B. , Hedrick Glen W. 
Published: April 2003

AbstractPolyethylene pinate‐4,4′‐biphenyldicarboxylate, polyethylene homopinate‐4,4′‐biphenyldicarboxylate, and polyethylene pinate‐terephthalate interpolymers were all prepared on a laboratory scale by ester‐interchange reactions. The polymer, fiber and film‐forming properties were examined. In the biphenyl systems, little difference was noted between pinate and homopinate; both formed filaments and films in the 40‐70 mole‐% pinic ranges. In the pinate‐terephthalate system this occurred in the 0‐40 mole‐% pinic range only. Both pinic and homopinic esters are thermally stable at polymerization temperatures of 250‐290 °C. for the time necessary to form high molecular weight interpolyesters. Their internal plasticization of highly crystalline, aromatic systems is useful in controlling the properties of interpolyesters from these systems. The crystalline melting points of polyethylene pinate‐terephthalate was a continuous, almost straight line relationship over the composition range studied. In the biphenyl systems, a discontinuity appeared in the melting point‐composition curves at 30‐40 mole‐% pinate or homopinate concentration. Possible reasons for this are suggested. An analytical method for determining 4,4′‐biphenyldicarboxylic acid is given.
The photolysis of polyethylene terephthalate
Authors: Osborn K. R. 
Published: April 2003

AbstractThe photolysis of films of polyethylene terephthalate has been studied over a wide variation of exposure conditions. The rate of polymer bond rupture was measured by the change in molecular weight. The rate of energy absorption upon exposure to near ultraviolet light was determined from an analysis of the emission characteristics of the light sources used and the absorption characteristics of the polymer. The overall quantum yield for the photolysis was found to be 5 × 10−4 bonds ruptured per photon. This quantum yield is shown to be independent of the wave length of the light absorbed in the spectral region studied. Further, analysis of the effect of film thickness on the rate of bond rupture indicates that the reactions are initiated only by the light absorbed in the strong ultraviolet absorption band characteristic of the pure polymer. The quantum yields for the photolysis of this polymer and others reported in the literature are compared and related to the effect of changes in physical state on the reactions of simple monomeric systems. It is concluded that the low values typical of many polymers are a result of rapid recombination of free radicals due to a low mobility in the solid state.
Melting characteristics of polyethylenes. A comparative study of low‐pressure and irradiated polyethylenes
Authors: Marker Leon , Early Robert , Aggarwal Sundar L. 
Published: April 2003

AbstractDilatometers of simple design were used to determine the relationship between specific volume and temperature for several different kinds of polyethylene: samples with densities of approximately 0.91 and 0.96 made at high and low pressures, respectively, and samples of low‐density material which had been irradiated with 106−108 roentgens supplied by 800‐kv. electrons. It was found that polyethylene made at low pressures is not only more crystalline than that made at high pressures, but also that it melts much more sharply. Despite the fact that irradiation raises the softening temperature of polyethylene, we have shown that the melting point of the crystalline regions of polyethylene is not thereby increased. It was found that in highly irradiated polyethylenes, the volume change with temperature deviates from linearity at 150°C. and rises rapidly at 170°C.
Determination of branching in a randomly branched polydisperse polymer
Authors: Kilb Ralph W. 
Published: April 2003

AbstractMethods are presented for the determination of degree of branching in a randomly branched polymer with tetrafunctional branch units. Typical examples of such polymers are irradiated linear polymers and copolymers of divinyl and monovinyl monomers. The most practicable method is found to be the comparison of the intrinsic viscosity of the branched polymer to the intrinsic viscosity of the corresponding linear polymer of the same weight‐average molecular weight. Agreement is found with previously published experimental data on polymers of known degrees of branching. It is also found that the ratio of the mean square radius to the weight‐average molecular weight for the polydisperse branched polymer is completely independent of degree of branching. Consequently, light‐scattering data alone on the polydisperse polymer is not sufficient to determine branching.
Rate of formation and decay of free radicals in γ‐irradiated polymethyl methacrylate by means of electron spin resonance absorption measurements
Authors: Ohnishi Shun‐Ichi , Nitta Isamu 
Published: April 2003

AbstractThe rate of formation of the free radicals in polymethyl methacrylate by γ‐irradiation, the rate of decay of the free radicals in vacuum and in the presence of air after irradiation, and also the rate of decay of the oxygenated radicals have been measured by means of electron spin resonance absorption measurements. The formation of the free radicals can be expressed in the beginning range of irradiation up to 10 hr. (7.1 × 106 r.) by the equation [R·] = 5.8 × 10−7 tanh (6.4 × 10−5t), where [R·] is the concentration of the free radicals in moles/cm.3 and t is the time of irradiation in seconds. Assuming the rate of formation follows the equation d[R·]/dt = k′I ‐ k[R·]2, where I is the dose rate, the rate constants, k′ and k, of the formation and of the decay of the free radicals are calculated to be k′ = 1.9 × 10−13 moles cm.−3 r−1 and k = 110 moles cm.3 sec.−1, respectively. The G‐value for the radical formation can be estimated to be 0.16 from this k′‐ value. A discussion on this small G‐value obtained is given in the paper, and it is supposed that the G‐value 0.16 may be that for the formation of the long‐living radicals in γ‐irradiated polymethyl methacrylate. The decaying processes of the radicals in vacuum and in the presence of air and those of the oxygenated radicals after irradiation are to be interpreted as reactions of the second order. The rate constants k′s of the decaying processes are estimated and tabulated. Comparing the k values under different conditions among themselves, some interesting features may be pointed out. The k‐value 110 during irradiation is very much larger than that 3.3 after irradiation. The k‐value 1130 in the presence of air is still larger. A discussion on these points is also given. In the case of decay of the radicals in vacuum, log k was plotted against reciprocal of absolute temperature and a straight line was obtained. From the slope, the activation energy was estimated to be 28 kcal./mole. When this value is compared with the activation energy 27 ± 10 kcal./mole estimated by Powles for the motions of chain segments in polymethyl methacrylate, it may be concluded that the motions of the chain segments are of primary importance for the rate determining step of the decaying reaction of the long‐living radicals.
Theoretical consideration of the effect of crystallinity on the viscoelastic properties of polyethylene
Authors: Takemura Tetuo 
Published: April 2003

AbstractFerry's reduction is applicable to amorphous polymers, but there is no reduction corresponding to Ferry's available for crystalline polymers. Here will be proposed a method of reduction based on a simple mechanical model, with the degree of crystallinity and draw ratio as its parameters. Confirmation of this method was attained from the stress relaxation curve of polyethylene for a draw ratio equal to 1. In this case, we have only to use log E + log T0/T − log Λ/(1 + Λ), log t − (ε/k) (1/T − 1/T0) + log T/T0 instead of log E, log t, where, Λ is the degree of crystallinity and ε′ the term corresponding to the activation energy of viscosity. A satisfactory master curve was obtained. The master curve due to frequency change could be obtained in the same way; however, this has not yet been confirmed, there being no appropriate data.