bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractTreatment 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

AbstractA 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

AbstractThe 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

AbstractMechanical 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

AbstractExtinction 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

AbstractJoint 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

AbstractThe 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

AbstractThermal 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

AbstractPolyalkyl 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.
The thermal degradation of polyacrylonitrile
Authors: Kennedy J. P. , Fontana C. M. 
Published: April 2003

AbstractThe 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

Abstractcis‐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

AbstractThe 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

AbstractThe 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

AbstractA “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

AbstractAccording 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

AbstractThe 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

AbstractThe 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

AbstractIf 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

AbstractHigh 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

AbstractThe 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

AbstractDeterioration 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

AbstractHeretofore, 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

AbstractThe 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.