bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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

Most 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

Crystalline 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

Preformed 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

Crystallization 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

The 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

New 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

Polyethylene 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

The 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

Dilatometers 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

Methods 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

The 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

Ferry'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.
cis‐trans Isomerization in polyisoprenes. Part IV. Conversion of gutta‐percha to a polymer which is rubber‐like at room temperature
Authors: Cunneen J. I. , Watson W. F.
Published: April 2003

Treatment of the partly crystalline polyisoprene gutta‐percha with thiolbenzoic acid, dibenzoyl disulfide, or sulfur dioxide transforms it into a polymer which is rubber‐like at room temperature. The vulcanizates obtained from treated gutta‐percha and ordinary gutta‐percha have been examined and found to differ markedly in their stressstrain properties. It is suggested that the above reagents cause trans‐cis isomerization in gutta‐percha and that these changes in configuration are responsible for the changes in physical properties.
Ultraclarification of solutions for light‐scattering measurements
Authors: Huque M. M. , Jaworzyn J. , Goring D. A. I.
Published: April 2003

A study of ultraclarification of aqueous solvents and solutions has been made by the ultracentrifugal technique of Dandliker and Kraut. Convenient optical arrangements for reducing stray scattering have been developed. Light‐scattering striations were found when solutions of cellulose trinitrate and lignin sulfonate were ultraclarified. With cellulose trinitrate, striations were accompanied by a downward bending of the θ = 0 line of the Zimm plot. The cause, elimination, and implications of these effects are discussed
Electron resonance measurements on radicals in gamma‐irradiated polydimethyl itaconate
Authors: Ovenall Derick W.
Published: April 2003

The electron resonance spectra of free radicals trapped in gamma‐irradiated polydimethyl itaconate are described. If the recent suggestions that only certain configurations of polymer radicals may be possible are taken into account, these spectra can be interpreted as arising from trapped propagating radicals.
The effect of molecular weight distribution on the physical properties of polystyrene
Authors: McCormick Herbert W. , Brower Frank M. , Kin Leo
Published: April 2003

Mechanical properties and melt viscosity have been measured on anionc polystyrene of narrow molecular weight distribution and thermal polystyrene of broad molecular weight distribution in an attempt to study the effect of molecular weight distribution. Tensile strength and elongation were found to depend upon some molecular weight between weight‐average and number‐average and not on number‐average molecular weight alone, as previously reported, while tensile impact strength depends upon weight‐average molecular weight, and modulus is essentially independent of molecular weight or molecular weight distribution. There is indication that high shear melt viscosity does not depend upon weight‐average molecular weight as does zero shear viscosity due to the effect of molecular weight distribution on non‐Newtonian flow characteristics. Complete analysis indicates little chance for a narrowing of the polymer distribution to permit an increased ease of fabrication without detrimental effects on the mechanical properties.
The optical behavior of spherulites in crystalline polymers. Part II. The growth and structure of the spherulites
Authors: Keith H. D. , Padden F. J.
Published: April 2003

Extinction patterns observed in spherulites of a number of polymers are shown to be in good agreement with the theoretical extinction curves calculated in Part I. The results establish the existence of regularly twisting crystal orientation in many of these spherulites. In the case of polyethylene the morphology of the spherulites is discussed in detail. Some consideration is given to the mechanisms by which fibrous spherulites are formed in polymer melts. Evidence is presented for the view that radiating fibrils grow and branch as fine dendritic crystals. Preferred molecular orientations in polymer spherulites are explained qualitatively on this basis.
Molecular distributions in polycondensations involving unlike reactants. VI. Independently distributed multivariate distributions
Authors: Case L. C.
Published: April 2003

Joint distributions and number‐ and weight‐average molecular weights have been derived for a number of independently distributed multivariate distributions. Use has been made of the fact that the means and variances of independent distributions are additive. It is shown that the ratio of the weight to number‐average molecular weights of an independently distributed multivariate distribution can be given in the following form:

where M̄ is the weight‐average molecular weight of the ith distribution. M̄ is the number‐average molecular weight of ith monovariate distribution.

In certain cases, the above expression is shown to be a very useful one.
Copolymerization of acrylonitrile and vinyl pyridine
Authors: Iwakura Y. , Tamikado T. , Yamaguchi M. , Takei K.
Published: April 2003

The copolymerization of acrylonitrile with 5‐ethyl‐2‐vinyl pyridine, 2‐vinyl pyridine, and 4‐vinyl pyridine has been investigated. The copolymer compositions have been determined by the titration of the copolymers in nonaqueous solvents with perchloric acid in glacial acetic acid, using methyl violet as an indicator. The reactivity ratios r1 and r2, respectively, have been determined in the three systems: AN/5‐ethyl‐2‐VP, (0.02 ± 0.02 and 0.43 ± 0.05); AN/2‐VP, (0.113 ± 0.002 and 0.47 ± 0.03); and AN/4‐VP, (0.113 ± 0.005 and 0.41 ± 0.09). The Q–e values for individual monomers have been calculated and compared with each other. The data obtained present no evidence for different reactivities of 2‐ and 4‐VP. The data shows that 5‐ethyl‐2‐VP has reactivity similar to those of above two monomers, but some difference caused by its ethyl group has been found. It has been also shown that the reactivity of 5‐ethyl‐2‐VP is quite identical with that of styrene.
Chain transfer of styrene and p‐chlorostyrene with benzaldehyde and p‐chlorobenzaldehyde
Authors: Platau G. , Eirich F. R. , Mesrobian R. B. , Woodward A. E.
Published: April 2003

Thermal polymerization of styrene and of p‐chlorostyrene at 100°C. in benzaldehyde and p‐chlorobenzaldehyde has been investigated. Intrinsic viscosities of the resulting polymers and per cent conversion‐time determinations have been made and are used to obtain DFn and second‐order rate constants, respectively, as functions of monomer concentration for the four systems. Chain transfer constants for each monomer in the two solvents and Qtr and etr values for benzaldehyde and p‐chlorobenzaldehyde are calculated and the results discussed.
Comparison of unperturbed molecular parameters of methacrylate polymers
Authors: Chinai Suresh N. , Valles Richard J.
Published: April 2003

Polyalkyl methacrylate polymers were prepared by the emulsion technique and fractionated. The intrinsic viscosity molecular weight relations were established in several ideal solvents. Light scattering determinations were run on polyalkyl methacrylates in an ideal and a nonideal solvent. The results of this experiment have proven that neither size nor shape of the solvent molecules has an effect on the dimensions of the unperturbed polymer. Also, it was shown that the unperturbed polymer dimensions are not altered by the choice of mixed or single theta solvents. It was found that the degree of chain extension increases as the size of the pendant groups (methyl, ethyl, and n‐butyl) increases.
Effects of temperature on the titration curve and molecular extension of polyelectrolytes
Authors: Ise N.
Published: April 2003

The temperature dependence of the potentiometric titration curve of a polyelectrolyte was analyzed in terms of an interionic interaction of theory. The extensionthe macroion in solutions was found to decrease with increasing temperature, in conformity with the temperature variation of the viscosity.
The thermal degradation of polyacrylonitrile
Authors: Kennedy J. P. , Fontana C. M.
Published: April 2003

The thermal degradation of polyacrylonitrile was studied in vacuum. A very rapid, explosive type of chemical transformation was found at 265°C., as indicated by sudden changes in color, infrared absorption, x‐ray diffraction, solubility, density, weight loss, and appearance. This reaction is discussed in terms of a free‐radical, branched‐chain mechanism and also in relation to a possible means of measuring degree of isotactic order along the polymer chain.
cis‐trans isomerization in polyisoprenes. Part V. The isomerization of natural rubber, gutta‐percha, squalene, cis‐ and trans‐3‐methylpent‐2‐ene, and cis‐polybutadiene, and its quantitative estimation
Authors: Cunneen J. I. , Higgins G. M. C. , Watson W. F.
Published: April 2003

cis‐trans isomerizations have been effected in natural rubber, gutta‐percha, squalene, cis‐ and trans‐3‐methylpent‐2‐ene, and cis‐polybutadiene by treatment with thiol acids, sulfur dioxide, and allied reagents. Natural rubber, and gutta‐percha, and cis‐ and trans‐3‐methylpent‐2‐ene have been converted into equilibrium mixtures of similar isomeric composition (57% trans at 140°C.). A sensitive infrared method of analysis has been developed for estimating cis and trans double bonds in polyisoprenes.
The correlation between activities of polyelectrolytes, measured by the light‐scattering and osmotic methods
Authors: Alexandrowicz Z.
Published: April 2003

The aim of this work was to demonstrate the clear‐cut correlation between the results of light‐scattering and osmotic measurements, primarily in the case of polyelectrolytes. The correlation is expressed to terms of formulas whose forms are adapted to the specific nature of each of the several possible kinds of comparison. Experimental results of both methods are given for water solutions of ionized PMA, PAA, and BSA. A special technique for the optical clarification was found to be indispensable for obtaining reasonably reliable light scattering results. The osmotic measurements were carried out in a special concentration osmometer. The osmotic coefficients ϕ, calculated from the results of both methods, are compared and found to be in reasonable accord. This justifies, in our belief, the use of light scattering as a method for measuring the activities of ionized polyelectrolytes. The method of treating the results is shown to be advantageious also in the case of nonelectrolytes.
Light‐scattering measurement of the osmotic activity of a polyethylene glycol solution
Authors: Alexandrowicz Z.
Published: April 2003

The osmotic coefficients were determined for aqueous solutions of a polyethylene glycol sample (Carbowax 6000) by means of light scattering. An equation is given for a simple computation of this coefficient. Light scattering was determined in the concentration range 0.5–20%. Above 3%, the scattered intensities do not increase with concentration. The computed osmotic coefficients are unusually high. High osmotic pressures can thus be obtained with concentrated solutions of PEG‐6000.
The concentration osmometer
Authors: Alexandrowicz Z.
Published: April 2003

A “concentration osmometer” which is easy to operate and very simply constructed is described. The principle of the measurement is based on the comparison of the unknown solution to a standard (in this case, a solution of polyethylene glycol Carbowax 6000 in water) which has a known calibrated value of the activity of water. During the measurement, the concentration of the two solutions changes as a result of free flow of water across the dividing semipermeable membrane, while the pressure in both solutions remains equal. By measurement of the amount and the direction of flow, the concentration of the standard which would be in equilibrium with the unknown solution can be interpolated. Examples are given of experiments performed with solutions of ionized PMA. The apparatus described has been employed in a concentration range of activities 10−1 to 10−4 M.
Glass temperature of copolymers
Authors: Dimarzio E. A. , Gibbs J. H.
Published: April 2003

According to a recent theory of the glassy state, chain stiffness is the main determinant of the glass transition. In this paper the theory is applied to the problem of predicting the glass temperatures of copolymers of varying composition and therefore varying chain stiffness. It is found that a simplified treatment leads to an equation which is identical in form to the Gordon–Taylor equation but whose coefficients have a different physical significance. Evaluation of these coefficients requires knowledge of only the structures of the homopolymers. This simplified treatment can be applied to various types of copolymer systems but amounts to more of an approximation in the case of random copolymers of the addition (vinyl) type than in the case of random copolymers of the condensation type. The glass temperatures of the condensation copolymer system polyethylene adipate/terephthalate are predicted within experimental error. The average per cent deviation between theory and experiment for 10 well‐characterized vinyl type copolymer systems is found to be 6.4%. In order to illustrate the applicability of the equation to systems not normally considered as copolymeric, the glass temperatures of the polymer system poly‐n‐alkyl methyl methacrylate (varying n) are correlated.
Kinetics of spherulite and crystallite growth in isotactic polystyrene
Authors: Kenyon A. S. , Gross R. C. , Wurstner A. L.
Published: April 2003

The rates of spherulite and crystal growth in isotactic polystyrene have been studied as a function of temperature by microscopic, x‐ray, and density methods. The effects of molecular weight and degree of isotacticity upon the spherulite growth are shown. Degree of isotacticity is the predominant factor in growth rate. Maximum rate of spherulite growth was observed at 175°C., while the maximum rate of crystal growth was observed at 190°C. Some evidence exists that polystyrenes made with the use of heterogeneous catalysts of the Ziegler type consist of heterogeneous blocks of isotactic and atactic polymers rather than polyblends.
Hydrolysis of polyacrylamide and acrylic acid–acrylamide copolymers
Authors: Smets G. , Hesbain A. M.
Published: April 2003

The hydrolysis of polyamides has been studied in buffered acid solution at 110°C. at an amide concentration of 0.05 M. In the case of polyacrylamide, the reaction was carried out in acetate buffer at different values of the ratio r (acetic acid/sodium acetate). The initial velocity is low and is proportional to the concentration of acetic acid; the rate constant is equal to 2.6 × 10−6; this reaction accelerates, however, as soon as the degree of conversion exceeds 3 to 5%. In the case of copolymers of acrylamide and acrylic acid (r1 = 1.38 and r2 = 0.36, respectively), the reaction proceeds in two distinct steps, of which the first is about 50 to 100 times more rapid than the second. By carrying out the reaction with copolymers of different composition (70, 74.5, 85, and 88 mole‐% acid) and varying the degree of neutralization for each (r = 2, 10, and 49), it is shown that the rapid first step results from the interaction between an amide group and an undissociated, directly neighboring acid group, which moreover must be present in a welldetermined stereochemical position. The stereospecificity of the kinetics of this reaction was demonstrated by the difference in the behavior of two copolymers of the same over‐all composition but different internal structure. The slow second step of the hydrolysis of the copolymer corresponds sensibly to the action on polyacrylamide by external acid; the retardation is a consequence of the fact that the requirements of vicinality and stereospecificity are not satisfied for the residual for the amide groups.
Interfacial polycondensation. II. Fundamentals of polymer formation at liquid interfaces
Authors: Morgan Paul W. , Kwolek Stephanie L.
Published: April 2003

If a solution of a fast‐reacting diacid halide in a water‐immiscible solvent is brought together with an aqueous solution of a diamine without stirring, a thin film of high polymer is formed at once at the interface. Polyurethanes and polyamides in particular form tough films which can be grasped and pulled continuously from the interface as a folded rope of film. This unstirred interfacial polycondensation not only provides a dramatic demonstration of polymer formation but has permitted the observation of polymerization behavior and the study of the effects of many variables upon the process. The polymer‐forming reactions proceed by nucleophilic displacement, and many have rate constants of at least 102–104 1. mole−1 sec. −1. Polymers derived from diamines were found to form in the organic solvent phase. Therefore the rate of polymer formation is controlled by the transfer of diamine from the aqueous phase. It is believed that the liquid interface does not have any beneficial orienting effect on the reactants but that it provides for the regulated flow of one reactant into an excess of the other. Furthermore, the aqueous phase provides for the removal of the interfering byproduct, hydrogen halide, from the polymerization site. Some of the interrelated variables which have been studied and which are discussed in relation to the physical mechanism are the solvent sensitivity of the polymer, partition coefficients of the reactants, reactant concentration, duration of the polymerization, and the addition of monofunctional reactants, detergents, and salts. The formation of polyphenyl esters is discussed briefly.
Interfacial polycondensation. V. Polyterephthalamides from short‐chain aliphatic, primary, and secondary diamines
Authors: Shashoua Victor E. , Eareckson William M.
Published: April 2003

High molecular weight polyterephthalamides were synthesized from a homologous series of primary diamines (ethylenediamine to hexamethylenediamine) by the interfacial polycondensation method. These polymers were found to be extremely high‐melting (300–450°C). and difficult to dissolve. Fibers were prepared by dry spinning from solutions in trifluoroacetic acid. A study of the polymer melting points and the fiber modulus as a function of the diamine chain length showed an alternation of properties with the number of carbon atoms, odd or even, in the diamine chain. All the polymers were highly crystalline and gave orientable fibers. As a comparison to the highly intractable polyterephthalimides from the primary diamines, a series of polymers from secondary diamines (N,N′‐dialkyl ethylenediamine to N,N′‐dialkyl hexamethylenediamine) were prepared. In contrast to the polymers from the primary diamines, these N‐alkylated derivatives were extremely soluble. In fact, some of them were even water‐soluble when prepared as low molecular weight products (ηinh ≤ 0.2). The N‐alkylated polymers melted at least 70°C. lower than the corresponding polyterephthalamides from the primary diamines. The N‐methylated derivatives were crystalline, while the N‐ethylated ones were amorphous. These results illustrate the importance of hydrogen bonding in determining the melting points and solubility characteristics of polymers.
Interfacial polycondensation. VI. Polyamides based on 4,4′‐sulfonyldibenzoic acid
Authors: Stephens C. W.
Published: April 2003

The preparation of eleven soluble polyamides based on 4,4′‐sulfonyldibenzoic acid by interfacial polycondensation with the use of aliphatic and alicyclic diamines is reported. Polymer melt temperatures of those polyamides prepared from aliphatic diamines decreased with increasing chain length and amount of chain branching in the diamine. The usual odd‐even alternation of melting points was noted. Cyclic secondary diamines gave higher‐melting polyamides than straight‐chain diamines, despite the lack of hydrogen bonding. Solubility decreased with increasing melting point, except for the polyamides based on cyclic diamines, which were both soluble and high‐melting. Fiber properties are reported for those polymers which were spun.
The mechanism of poly(vinyl chloride) stabilization by barium, cadmium, and zinc carboxylates. I. Infrared studies
Authors: Frye Alfred H. , Horst Raymond W.
Published: April 2003

Deterioration in poly(vinyl chloride) is due primarily to zipperlike elimination of hydrogen chloride from the polymer chain, with formation of colored and easily oxidizable polyenes. Baum and Wartman have shown that elimination is initiated by rupture of certain particularly labile carbon‐chlorine bonds. The stability of poly(vinyl chloride) is enhanced by incorporation of various additives, among which are the barium, cadmium and zinc salts of certain carboxylic acids. To gain insight into the way these compounds retard deterioration, the infrared spectra of a series of poly(vinyl chloride) films, with and without admixed barium, cadmium, and zinc 2‐ethylhexanoate, were studied after various heat treatments. These studies have shown the presence of a band at 5.75 μ in the spectra of the films containing the 2‐ethylhexanoates which is absent from the spectra of the unmixed components. The intensity of the band varies with the particular salt, temperature, and duration of heat treatment. Absorption at 5.75 μ is attributed to the carbonyl stretching frequency of an aliphatic ester. The spectra of vinyl acetate–vinyl chloride copolymers show such bands. We propose that the stabilizing action of barium, cadmium, and zinc salts of carboxylic acids arises in part from esterifying displacements of labile chlorine atoms.
Existence of a sharply defined maximum relaxation time for monodisperse polystyrene
Authors: Tobolsky A. V. , Murakami K.
Published: April 2003

Heretofore, the master stress relaxation curves of amorphous polymers could only be resolved by approximation methods into a continuous distribution of relaxation times. This is obviously not entirely satisfactory in all cases, e.g., for Maxwellian stress decay or if the Rouse distribution for the rubbery flow region were truly applicable. A new procedure (termed Procedure X) is proposed where is favourable cases the master stress relaxation modulus in the rubbery flow region can be resolved in to a discrete distribution of relaxation times, including a well defined maximum relaxation time. This procedure was applied to monodisperse and polydisperse polydisperse polystyrene, the latter of heterogeneity index 1.5. It appears that Procedure X gives resonably well defined values for at least the two highest relaxation times in these two cases.
Molecular orbital considerations on the reactivities of vinyl compounds. II. Ionic polymerizability
Authors: Fueno Takayuki , Tsuruta Teiji , Furukawa Junji
Published: April 2003

The β‐carbon localization energies Lβ+ and Lβ− for electrophilic and nucleophilic additions to vinyl compounds, respectively, were calculated according to the simple LCAO MO method and were compared with the experimental results so far reported on the ionic polymerizability of these compounds. The larger the cationic (or anionic) polymerizability of a monomer, the smaller was the value of Lβ+ (or Lβ−) for it. It was also verified in terms of localization energies that the vinyl monomers which are not amenable to radical polymerization tend to polymerize more easily by either of the two ionic mechanisms. By applying Jaffé's first order perturbation method, Lβ+ and Lβ− of each monomer were expressed as functions of the Coulomb integral parameters of the heteroatoms involved. Although the values of Lβ+ and Lβ− did not agree perfectly with the direct results obtained from secular equations, the discrepancy in both cases could be minimized when each of the Coulomb integral parameters employed in the perturbation approximation was empirically taken as 0.6 times as large as that used in the direct variation calculation. The procedure was successfully applied to the interpretation of the substituent effect on the cationic polymerizability of styrene.
Molecular orbital considerations on the reactivities of vinyl compounds. III. Polarographic reduction
Authors: Fueno Takayuki , Asada Kameo , Morokuma Keiji , Furukawa Junji
Published: April 2003

The polarographic half‐wave reduction potentials E1/2 of several vinyl (including vinylidene) monomers were measured and were discussed on the basis of the molecular orbital theory. The current‐voltage curves were determined in a 0.05 M solution of tetra‐n‐butylammonium iodide in the mixture of dioxane and water (3:1 by volume). The values of E1/2 were read against the saturated calomel electrode. It was found that E1/2 is correlated with xiv by E1/2 = 2.33 xiv−0.80, where xiv stands for the root of the MO secular equation for the π‐electronic system of the vinyl monomer corresponding to the lowest vacant level. Some of the monomers could not be reduced in the range of the applied potential less negative than − 3.0 volt vs. SCE, which was reasonably explained by their relatively large values of −xiv. It was suggested that the polarographic reducibility of vinyl monomers is roughly parallel to their anionic polymerizability. Furthermore, the lowest vacant π‐orbital energies of vinyl compounds were calculated according to the first order perturbation method. The results obtained thus were in good accordance with those calculated directly from the secular equations. It was also shown that the first ionization potentials of vinyl compounds were roughly related to their highest occupied π‐electronic energies.
The effects of attenuation and secondaray scattering on the determination of the second virial coefficient by light scattering
Authors: Carpenter D. K.
Published: April 2003

The effects of attenuation and secondary scattering on the determination of molecular weights and second virial coefficients by light scattering are investigated. The correction to the molecular weight due to these effects is small unless the reference standard has a high turbidity. The correction to the second virial coefficient is negligible in good solvents but becomes relatively more important as the ⊖‐condition is approached. Determination of the ⊖‐temperature for a polymer‐solvent system by light scattering can be in error by as much as several degrees under certain conditions, viz., large cells, large values of the constant H = (32π3n20/3Naλ4)(dndc)2, and small values of the Flory‐Krigbaum entropy parameter ψ1.
Light‐scattering measurements on selected polyamides (nylons)
Authors: Beachell Harold C. , Carlson Douglas W.
Published: April 2003

A series of polyamides (nylons) formed by polymerizing an aliphatic diamine with an aliphatic acid or by polymerizing an aliphatic amino acid has been investigated by light‐scattering techniques in the solvent 2,2,3,3‐tetrafluoropropanol with 0.1 N sodium trifluoroacetate, as added electrolyte. The series investigated consisted of nylon 6, nylon 66, nylon 610, and Zytel 61. The refractive index gradient (dn/dc) for these polyamides was found to be 0.190 cm.3/g., and the light‐scattering constant H was taken as 9.59 X 10−6 cm.2./g.2, both values being determined for 4358‐A. incident radiation. Molecular weights, second virial coefficients, and molecular dimensions have been determined for theses polymers.
The morphology of semicrystalline polymers. Part I. The effect of temperature on the oxidation of polyolefins
Authors: Hawkins W. L. , Matreyek W. , Winslow F. H.
Published: April 2003

Oxidation rates of several uninhibited polyolefins were determined in the temperature range 40–140°C. The logerithm of the induction period increased linearly with 1/T, no changes in slope being noted in the melting range with polythylene. At the lower temperatures branched polythylenes were more susceptible to oxidation than the linear types. In the solid statem, oxygen uptake of both modifications were substantially less than that observed for the molten polymer. The amount of oxygen reacting in the solid state was shown to be inversely proportional to the per cent crystallinity, which indicates that reaction with oxygen takes place only in the amorphous region of these semicrystalline polymers. Isotactic polypropylene was only slightly less reactive than the atactic form, and both were more reactive than polyethylene. The effect of temperature on the activity of several moderately effective anotioxidants in branched polythylene was measured. These data also conform to linear Arrhenius‐type plots. Activation energies were specific, however, for each antioxidant and varied considerably; thus, an antioxidant rated as relatively ineffective under accelerated testing conditions could be quite effective within the temperature range over which it would normally be used as a polythylene protectant. Carbon black, which is comparable with some to the less effective thermal antioxidants under accelerated test conditions, provided an unexpected high order of protection for polyethylene below the melting point. This increased protection in the solid state was attributed to the impermeability of the crystalline phase to oxygen and increased concentration of the bulky carbon (antioxidant) particles in the amorphous region.
Electron microscope observations on microgel and linear macromolecules of polyacrylonitrile
Authors: Heyn A. N. J.
Published: April 2003

The presence of microgel particles, which were expected on the basis of other indirect measurements to occur in polyacrylonitrile solutions, is directly demonstrated in these solutions with the electron microscope. The particles are spherical in shape and have a uniform size of about 500 A. These microgel particles are probably crosslinked or branched giant molecules. On the side of these particles linear molecular threads are observed. Their bundling together into microfibrils is also observed.
The effect of hydrogen bonding addends on the dilute solution viscosity of poly(acrylamide) and unionized poly(acrylic acid) and poly(methacrylic acid)
Authors: Eliassaf J. , Silberberg A.
Published: April 2003

The effect of various addends on the specific viscosity of dilute aqueous unionized poly(methacrylic acid) (PMA) solutions, unionized poly(acrylic acid) (PAA) solutions, and poly(acrylic acmide) (PAAm) solutions was investigated. The addition of sodium and lithium chloride decreases the specific viscosity of PMA and PAA but leaves PAAm unaffected. The addition of ethanol to aqueous unionized PMA causes a decrease in specific viscosity up to 15% of the addend and an increase at higher alcohol content. The specific viscosity of PAA is increased and that of PMA decreased by ethanol. Urea and acetic acid addition decrease the specific viscosity of PMA and increase that of PAA. Urea does not affect the specific viscosity of PAAm. Guanidine hydrochloride addition decreases the specific viscosity of PMA. Perfluorooctanoic acid addition increases and caprylic acid decreases the specific viscosity of PMA, whereas neither of them affects PAA. It is assumed that the specific viscosity is a measure of the degree of intramolecular bonding. The results are discussed on the basis of a model which considers separately the effect of the addend on the polymer and on water. It is shown that for intramolecular bonding to decrease, (fA/fW)exp {−(Δμ°A − Δμ°W)/kt} must be larger than unity. In this expression, which represents the effectiveness of addend in replacing water on the chain, fA and fW are the activity coefficients of addend and water, respectively, and (Δμ°A − Δ°W) is the free energy change when addend replaces water on the chain. Results from the literature are included in the discussion.
Birefringence in swelling crosslinked polymer beads
Authors: Gurnee Edward F.
Published: April 2003

The radial distribution of birefringence in a swelling polystyrene–divinylbenzene copolymer bead is measured from the optical patterns observed with a polarizing microscope. This birefringence arises from the restraining influence of the nonswollen core on the exterior shell of gel. It is found that the birefringence is negative in sign, and exhibits a sharp maximum at the gel‐core interface.