bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarity in copolymerization
Authors: Ham G. E.
Published: April 2003

Independent means of assaying free radical copolymerization polarity (e) values from ionic copolymerization data are outlined. Interpretation of ionic (carbanionic and carbonium) copolymerization data in general in the light of these same e values is discussed. An extension of Wall's equation:

to allow prediction of ionic copolymerization reactivity of untested combinations is offered. For carbanionic systems:

where P1 and P2 are empirical functions of the polarity e of Alfrey and Price. For carbonium systems:

where N1 and N2 are different empirical functions of the polarity e. Advantages and limitations of the technique are discussed.
How to treat tensile data of rubber. II. A computational method
Authors: Kase Shigeo
Published: April 2003

An effective method for dealing with tensile data of rubber, based on previously described frequency distributions, is presented and its advantages over graphic methods are described.
Polymers and group interactions. I. Synthesis of polyampholytes
Authors: Vrancken M. , Smets G.
Published: April 2003

It is possible to obtain a polyampholyte characterized by the presence of primary amine and carboxylic functions by a method based on the mutual reaction of functional groups along the polymeric chain. The great advantage of this method is the production of copolymers of a new type, from which the internal structure is well defined. In the present case the method is based upon interaction of an acyl chloride unit with a neighboring isocyanate function; these isocyanate functions have been introduced into the chains by two different methods, the Curtius reaction (sodium azide on polyacroyl chloride) and the Lossen reaction (hydroxylamine base on polyacroyl chloride). The solvents used were dioxane and dimethylformamide; the reactions were performed at ebullition. Higher boiling solvents yield an increasing amount of insoluble material. Both syntheses give end‐products with the same properties. The structure of the polymers has been established from conductometric and potentiometric titration curves and also from nitrogen analysis. It was found that the interactions produce the formation of rings along the chain, and that these interactions are limited, as can be foreseen from statistical reasons; the residual groups remain free and become carboxylic functions after hydrolysis, or they react further and are transformed into amino functions. The final products are to be considered as copolymers of vinylamine and acrylic acid with a predominant alternate structure, and in which a given amount of amino groups have reacted with a neighboring acid function yielding lactam rings. However, these pyrrolidone units may be easily opened by alkaline hydrolysis, yielding thereby a polymeric chain with free amino and carboxylic functions, from which the proportions are approximately equivalent at high nitrogen content (12.5–13% N2). At lower nitrogen content the proportion of free carboxylic functions predominates; e.g., at 9.8% N2 there is an excess of 24% acidic functions. Determinations before and after hydrolysis allow the establishment of the internal structure of the copolymers; the proposed structure has been confirmed by benzoylation and deamination reaction and analysis of the benzoylated and deaminated copolymers.
Polymerization of diallyl phthalate
Authors: Haward R. N.
Published: April 2003

Using a simple statistical model, the probability of intramolecular reaction is calculated for the polymerizing diallyl phthalate molecule. The calculation is based on the assumption of the free rotation of bonds and a restriction of the chains considered to 9 and 11 links. Allowance is made for the different types of terminal structure produced during the reaction. The result agrees with the experimental work of Simpson in that an appreciable probability is found. (Theoretical 31%, experimental 41%, saturated groups). It is probable that the accuracy of the results obtained has been increased by reason of the fact that different imperfections in the model affect the result in opposite senses.
How to treat tensile data of rubber. III. Least squares adjustment
Authors: Kase Shigeo
Published: April 2003

An alternative method based on least squares adjustment is presented for evaluating tensile data on rubber.
Adsorption of high polymers from solution on to solids. II. Adsorption of polystyrene on charcoal
Authors: Jellinek H. H. G. , Northey Helen L.
Published: April 2003

Rates of adsorption of polystyrene on to charcoal from methyl ethyl ketone solutions are influenced by water present in the solvent causing resting periods. These resting periods disappear when water‐free solvent is used. The type of adsorption isotherm and molecular weight relationship are not influenced by the presence of water. The temperature coefficient for rate of adsorption is small.
The curing of silicone rubber with benzoyl peroxide
Authors: Bueche A. M.
Published: April 2003

The formation of crosslinks in silicone rubber by benzoyl peroxide was studied by tension and swelling techniques as a function of curing conditions and filler content. The ability of benzoyl peroxide to form crosslinks was found to decrease markedly as the peroxide concentration was increased. The peroxide seems to form crosslinks in an amount independent of the concentration of the silica filler. High crosslink concentrations were found to be necessary to fully utilize the polymer‐filler attachments. Values for the bulk and solution densities of silicone gum and the specific volume of the filler in silicones were determined. The melting point of benzoyl peroxide immersed in silicone gum is reported. The aging of silicone gum at 150°C. in air was found to neither increase nor decrease the number of crosslinks.
Ring opening in lactam polymers
Authors: Conix André , Smets G.
Published: April 2003

Apparent first‐order rate constants and activation energies for the alkaline hydrolysis of polyvinylpyrrolidone, polyactam, vinylpyrrolidone‐maleic acid copolymer, N‐isopropyl‐γ‐valerolactam, butyrolactam, and pyrrolidone‐N‐acetic acid were determined in order to study the influence of structure on the stability of the lactam ring. It was found that the behavior toward alkaline hydrolysis of polyvinylpyrrolidone closely resembles that of its low molecular analogue N‐isopropyl‐γ‐valerolactam. It has been shown that a carboxyl function substituted near the lactam ring has a favorable influence on the ease of hydrolysis. Alkyl substitution on the lactam nitrogen, however, makes the lactam more resistant against hydrolysis.
Non‐Newtonian viscosities in dilute aqueous solutions of sodium carboxymethylcellulose
Authors: Fujita Hiroshi , Homma Terutake
Published: April 2003

The reduced viscosity vs. concentration relation was measured for sodium chloride solutions of sodium carboxymethylcellulose (Na‐CMC of DP ≓ 400 and DE ≓ 0.7) in a range of low concentrations (0.003 to 0.09 g./100 ml.), and the data obtained were analyzed following the procedure of Pals and Hermans. The results confirmed in many aspects findings which had previously been made in the literature, and supplied values of the necessary molecular quantities for our own sample. They indicated that our Na‐CMC molecule was relatively uncoiled even in solutions of high ionic strength. The Huggins slope constant was found to increase approximately linearly with increasing reciprocal of the ionic strength of the solution. Next, the shear dependence of reduced viscosity in dilute solutions of this polyelectrolyte was investigated by the use of a viscometric apparatus which was especially designed for accurate measurements at low shear rates. The shear rate region investigated was from about 50 to 1000 sec.−1. The measurements were made on salt‐free solutions and on solutions of constant ionic strength; in both cases only the regions of sufficiently low concentrations were treated. In the salt‐free solutions the ηsp/C vs. q (q is shear rate) curves showed an upward curvature rather than a quadratic dependence at the limit of shear rate. In this case, the initial slope of each curve increased markedly with increasing dilution. The plots of ηsp/C vs. q for solutions of constant ionic strength (ca. 0.0015 mole/l.) were approximately represented by straight lines within the concentration range investigated. The slope of the straight lines decreased regularly with increasing dilution. Some evidence that these plots have a horizontal initial tangent was observed, but this was never conclusive due to the paucity and inaccuracy of exprimental data at shear rates smaller than 100 sec.−1. The intrinsic viscosity obtained from ηsp/C vs. C curves at constant shear rates for the isoionic system was independent of q. From these findings it was realized how markedly the viscous behavior in dilute solutions of the polyelectrolyte studied was influenced by the addition of small amounts of neutral salt, not only in viscosity value itself but also in its shear rate dependence. Our data and results herein presented were concerned only with a sample of one (average) molecular weight and one degree of etherification. More data, therefore, are needed on samples of varying degrees of polymerization and etherification before a more definite understanding of the problem herein treated is possible.
Diffusion of polyelectrolytes in salt‐free solutions
Authors: Kedem O. , Katchalsky A.
Published: April 2003

The diffusion of polymethacrylic acid in salt‐free aqueous solution has been investigated. At high degrees of ionization the diffusion coefficient is independent of concentration and of the degree of polymerization. However, it depends markedly on the degree of ionization. The hydrodynamic resistance of the polymer ion is calculated from the diffusion coefficients by allowing for the osmotic behavior of the polyelectrolyte in solution. The results, which are discussed, indicate a rodlike shape for the molecule at high degrees of ionization. At zero degree of ionization (polymethacrylic acid in an acid medium) the diffusion coefficient is nearly independent of concentration. It is inversely proportional to the square root of the degree of polymerization, showing that the un‐ionized molecule is not rinsed by the solvent. A quantitative comparison of the diffusion coefficient, with the intrinsic viscosity of the same solution, shows that there is fair agreement with the theory of Kirkwood and Riseman.
Branching in polybutadiene
Authors: Pollock D. J. , Elyash L. J. , DeWitt T. W.
Published: April 2003

A detailed study has been made of the intrinsic viscosity‐molecular weight relationship for a polybutadiene prepared at 50°C. and one prepared at 5°C. Original fractions were at least twice refractionated from very dilute solutions in an attempt to obtain fairly sharp distributions. Fox‐Flory K constants are observed to decrease with increasing molecular weight in each case, and the intrinsic viscosity‐molecular weight plots show a curvature. This is interpreted to be a result of branching. A method of plotting the data is proposed which simultaneously yields the K for unbranched material and an estimate of the degree of branching. It is estimated that, in polybutadiene prepared at 50°C., one out of 6500 monomer units is involved in a branch, and that in 5°C. polybutadiene, one out of 10,000.
Hydroxyethyl nylon, a new flexible superpolyamide derivative
Authors: Haas Howard C. , Cohen Saul G. , Oglesby Albert C. , Karlin Estelle R.
Published: April 2003

Interesting new derivatives of nylon with unusual properties were prepared by treating nylon with ethylene oxide. These graft copolymers have greatly enhanced flexibility but still retain the high melting character of the original nylon. A hydroxyethyl 6‐6 nylon containing 50% combined ethylene oxide was found to be flexible and useful over a very large temperature range, the polymer having a melting point of 221°C. and an apparent second‐order transition point below −40°C. Analyses, carried out to study the distribution of combined ethylene oxide residues in these materials, indicated a tendency toward limited substitution of the nylon backbone and rather long average polyethylene glycol branch lengths. The distributions of the combined ethylene oxide residues are correlated with the nature of the starting materials. Synthetic methods, analyses, infrared spectra, solubilities, viscosity behavior, melting point and second‐order transition point data, stress‐elongation results, and moisture permeabilities of these materials are reported. The hydroxyethyl derivatives are more hydrophilic than the unsubstituted linear nylons. Hydroxyethyl nylon should also be considerably more stable than Type 8 nylon since it does not contain the labile N‐methoxymethyl linkage. A striking contrast in properties exists between hydroxyethyl nylon and derivatives of nylon prepared in solution under homogeneous conditions. This difference in properties is attributed to a nonrandom distribution of branch sites along the chain in the case of hydroxyethyl nylon. This nonrandomness is due to the heterogeneous nature of the ethylene oxide‐nylon reaction and to the formation of primary hydroxyl groups which are more reactive toward ethylene oxide than the original amide NH groups.
Vinyl polymerization. V. Decomposition of sym‐substituted benzoyl peroxides in the presence of dimethylaniline
Authors: Imoto Minoru , Choe Seuckon
Published: April 2003

A study of the rates of the decomposition of benzoyl peroxide and substituted benzoyl peroxides in the presence of dimethylaniline was made. It was proved that the initial rate (v0) of the decomposition could be expressed by the equation v0 = k2P0A0. P0 and A0 are the initial concentrations of peroxide and dimethylaniline, respectively. In the decomposition of substituted benzoyl peroxides, the values of v0 fitted nicely with Hammett's equation. It was confirmed that electron‐attracting substituents accelerated the decomposition and electron‐repelling groups retarded it. As an intermediate of the reaction of benzoyl peroxide with dimethylaniline, a loose complex may be produced by coordination of the electron lone pair in the nitrogen atom with the peroxidic central oxygen atom; through this intermediate, decomposition may occur. Finally, it was assumed that the driving force for the decomposition of benzoyl peroxide was an electrostatic repulsion between the two oxygen atoms of the carbonyl groups (but not of the central peroxidic group).
Fluorine‐containing polymers. II. 1, 1‐dihydroperfluoroalkyl acrylates: Preparation of monomers1
Authors: Codding D. W. , Reid T. S. , Ahlbrecht A. H. , Smith G. H. , Husted D. R.
Published: April 2003

Acrylate esters of seven n‐1,1‐dihydroperfluoroalkanols have been synthesized. The esters are: 1,1‐dihydroperfluoroethyl‐; 1,1‐dihydroperfluoropropyl‐; 1,1‐dihydroperfluorobutyl‐; 1,1‐dihydroperfluoropentyl‐; 1,1‐dihydroperfluorohexyl‐; 1,1‐dihydroperfluorooctyl‐; and 1,1‐dihydroperfluorodecyl acrylates. Since these alcohols were difficult to esterify using conventional procedures, acrylyl chloride or acrylic acid plus perfluoroacetic anhydride have been empolyed in this work.
Fluorine‐containing polymers. IV. Polymers of acrylates of fluorine‐containing ether alcohols
Authors: Bovey F. A. , Abere J. F.
Published: April 2003

A number of polymers of acrylates of fluorine‐containing ether alcohols were prepared and studied. The side‐chain structures investigated are: CF3CH2OCH2CH2OCO, CF2HCF2OCH2CH2OCO, CF2HCF2(OCH2CH2)2OCO, CF3CF2CF2CH2OCH2CH2OCO,
magnified image
and RfOCF2CF2CH2OCO, where Rf equals CF3, CF3CF2, CF3CF2CF2, and CF3CF2CF2CF2. Of these, the last group has glass transition and stiffening temperatures 20–25°C. lower than those of most of the others, together with the small swelling in solvents characteristic of the RfCH2OCO series. It is concluded that polymer behavior, particularly the modulus‐temperature and solubility characteristics, may be very profoundly affected by the nature of the side chains. An interpretation of the behavior of the polyacrylates of the fluorinated ether‐alcohols in terms of increased side‐chain flexibility due to ether “swivel joints” is attractive, but may not be justified.
Fluorine‐containing polymers. V. Light scattering and viscosity study of poly‐1,1‐dihydroperfluorobutyl acrylate
Authors: Rathmann G. B. , Bovey F. A.
Published: April 2003

Light scattering measurements in benzotrifluoride indicate that poly‐1,1‐dihydroperfluorobutyl acrylate (poly‐FBA) has been polymerized in emulsion and solution to molecular weights up to 40 million. If the polymerization is carried to high conversion, long chain branching results, presumably by chain transfer to the polymer. Intrinsic viscosities near 1.0 in benzotrifluoride for molecular weights of 10 million are explained largely on the basis of the high monomer molecular weight using Flory's equation relating molecular weight, intrinsic viscosity, and molecular dimensions. From the equation the intrinsic viscosity of a polymer should be expected to decrease roughly as the 3/2 power of the monomer molecular weight, if the increased bulk does not alter the chain flexibility. Long chain branching and the fact that benzotrifluoride is a poor solvent exaggerate the effect. Light scattering and intrinsic viscosity data indicate that the θ temperature for benzotrifluoride (that temperature at which solvent polymer interactions vanish) is only a few degrees below room temperature. Precipitation of poly‐FBA from dilute solutions near 15°C. confirms this fact. Methyl perfluorobutyrate is found to be a better solvent, but the value of the second virial coefficient and the exponent in the equation relating intrinsic viscosity to molecular weight are lower than predicted from swelling data. The freely jointed segment length has been calculated to be 15 carbon atoms, which is larger than reported for other rubbery materials. Short range interactions of the large side chains apparently result in a fair degree of chain stiffness which may be related to the high transition temperature of poly‐FBA relative to its hydrocarbon analog.
Fluorine‐containing polymers. VII. 1,1‐dihydroperfluoroalkyl acrylates: Compounding and properties of vulcanizates
Authors: Stedry P. J. , Abere J. F. , Borders A. M.
Published: April 2003

The homopolymer and butadiene copolymers of 1,1‐dihydroperfluorobutyl acrylate form a new class of vulcanizable elastomers with interesting and useful properties, of which solvent resistance is the most outstanding. The homopolymer (poly‐FBA), vulcanized by means of a polyfunctional amine in the presence of a reinforcing pigment, appears most promising because it offers the following unusual combination of desirable properties: (1) resistance to hydrocarbon solvents; (2) resistance to a variety of lubricants, hydraulic fluids, and similar high boiling liquids at temperatures up to 400°F.; (3) resistance to oxidation by ozone and fuming nitric acid; (4) fair stability and physical properties in air at elevated temperatures. It was shown that many of these properties depend upon compounding recipes and that further improvements can be anticipated.
Light scattering investigation of potato amylopectin
Authors: Witnauer L. P. , Senti F. R. , Stern M. D.
Published: April 2003

Light scattering measurements were made on amylopectin prepared from potato starch by two procedures. Potato starch dispersed in water at 90° and fractionated with mixed pentanols gave an amylopectin I having a weight‐average molecular weight of 36 million. Dispersion of starch by autoclaving at 120°, followed by nitrobenzene precipitation of amylose, yielded an amylopectin II with weight‐average molecular weight of 14 million. No evidence was found for dissociation of these amylopectins into smaller units in aqueous solution at concentrations as low as 10−6 g./ml., at elevated temperatures, or in sodium hydroxide solutions. Aggregation of amylopectin II occurred at potassium chloride concentrations above 5 × 10−4 molar. Marked reduction of molecular weight of amylopectin II resulted from treatment under a high rate of shear in a Waring Blendor. Acetylated II (40% acetyl content) was soluble in nitromethane, chloroform, acetone, dioxane, and acetonitrile. In all these solvents the molecular weight, corrected for acetyl, was close to 10 million. No evidence was found for an increase in reciprocal specific turbidity at low concentration which would parallel reported osmotic pressure results. Polydispersity was demonstrated by ultracentrifugal sedimentation patterns of amylopectin II, and by separation of amylopectin I into a series of fractions ranging from 7 to 73 million in molecular weight.
Studies on the validity of the Einstein viscosity law and Stokes' law of sedimentation
Authors: Cheng P. Y. , Schachman H. K.
Published: April 2003

Ultracentrifugal studies on polystyrene latex particles (PSL) in solutions of different densities prepared either from mixtures of H2O and D2O or from various concentrations of sucrose in water yielded a value, by interpolation, of 1.0520 for the density of solution in which the particles neither sediment nor float. Considerations of these results plus the nature of the particles lead to the conclusion that the partial specific volume of the polystyrene latex particles is (1/1.0520) cc./g., a value in agreement with the bulk specific volume of solid polystyrene. Evidence is presented for PSL to support the view that the effective hydrodynamic volume is equal to the partial specific volume, so that volume fractions can be determined from the partial specific volume and the dry weight concentration. Measurements of the viscosity of suspensions of polystyrene latex particles over a broad concentration range showed that the intrinsic viscosity was 2.5, in confirmation of the theory of Einstein. At concentrations above 2% by volume a square term in concentration, with coefficient about 10, and also a cubic term are needed to satisfy the data. From the partial specific volume of the latex particles and the value of the sedimentation coefficient extrapolated to infinite dilution, a value of 2640 ± 12 A. was calculated for the diameter of the particles from Stokes' law. This value is in excellent agreement with values obtained by electron microscopy, light scattering, and low angle x‐ray scattering. This agreement amounts to a satisfactory test of Stokes' law for particles not much larger than some of the viruses. Studies of the dependence of sedimentation coefficient on concentration indicate that existing theories are not completely satisfactory and that the influence of backward flow of liquid during the sedimentation of the solute particles is appreciable.
Particle size distribution in brominated Hevea latices
Authors: Schoon Th. G. F. , van der Bie G. J.
Published: April 2003

From electron micrographs of clonal latices and centrifuge fractions, the particle size distributions in Hevea brasiliensis latices have been measured. By means of this investigation–which was meant to be informative only–it has been possible to ascertain that the highly asymmetric size frequency distributions that are apparently present result from the existence of several size fractions, which each itself has a normal Gaussian distribution. The particle sizes are found as being multiples of whole numbers of either of the two particle sizes 58 mμ and 69 mμ. A possible explanation of this phenomenon is that the larger particles form by clustering of the smaller particles in a grape‐like arrangement, without actual coalescence or fusing together. From the experiments it may be supposed that the particle size distribution of latex may have an influence on its centrifuging qualities.
Formation and properties of polymer carbon
Authors: Winslow F. H. , Baker W. O. , Pape N. R. , Matreyek W.
Published: April 2003

Divinylbenzene (48%)/ethylvinylbenzene copolymer was converted to a series of pyrolytic derivatives. Enough of the carbon bond network remained intact throughout thermal rearrangement and condensation to retain the original gross shape of the copolymer in the final polymer carbon. Although a carbon residue (6% by weight) was obtained by direct heating of the copolymer, yields were increased eightfold by preoxidation or prechlorination. Such an alteration of thermal degradation is obviously a complex process involving both “inhibition,” in the ordinary sense, and a considerable contribution toward an increased valence network density. As a consequence, the average molecular weight of volatile fragments evolved during carbonization is inversely proportional to the oxygen content of the original hydrocarbon polymer. Pyrolysis of divinylbenzene copolymer, containing 18% oxygen, resulted in a 50% volume shrinkage, 50% weight loss, and a 100% density gain. Unless these data are attributable to extensive microporosity, it is difficult to account for the sorption of up to 3 cc. of helium gas per gram of polymer carbon at 30°C. and 600 mm. pressure; and calculated surface areas as large as 1400 sq.m./g. Abrupt changes in the progress of polymer carbon formation occurred between 600 and 700°C. The residue became rigid; vigorous evolution of volatile products, principally hydrogen, suddenly diminished; and paramagnetic resonance absorption (unpaired electron concentration) dropped about tenfold while d.c. resistivity decreased 106 ohm cm. In this region, also, x‐ray patterns were most diffuse, exhibiting no maxima characteristic of carbon scattering in either hydrocarbons or condensed rings. Finally, the x‐ray patterns of polymer carbon intermediates became less diffuse in samples prepared at 700°C. or above. Yet, scattering indicated the presence of crosslinked graphitic layers of such stability that reordering or true graphitization did not occur at 2400°C.
Reinforcing effect of condensation polymers on rubber in connection with their particle size
Authors: Houwink R. , Van Alphen J.
Published: April 2003

Evidence is brought forward that the noticeable reinforcing effect by cyclized rubber, if added as a filler to natural rubber, is bound to a certain minimum particle size of the cyclized rubber. It is further shown that the reinforcing effect of some condensation polymers is enhanced if chemical bonds with the rubber are formed. The reinforcing effect by resins is connected with their hardness.
Determination of the shape of gamma‐globulin by means of the x‐ray low‐angle method
Authors: Kratky O. , Porod G. , Sekora A. , Paletta B.
Published: April 2003

A short review is given of the development of the theory and of the new experimental technique of x‐ray low‐angle scattering. The study of human γ‐globulin leads to a cylindrical particle of about elliptical cross section with axes of 19 and 57 A. and with a length of 230–240 A. The volume is found to be 1.98 × 105 A.3, which involves a molecular weight of 1.62 × 105 in satisfactory agreement with the value found by ultracentrifuge measurements.
The viscosity slope constant k′—ternary systems: Polymer–polymer–solvent
Authors: Cragg L. H. , Bigelow C. C.
Published: April 2003

The viscosity slope constant k′, i.e., \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\lim }\limits_{c \to 0} \frac{{d\left( {{{\eta _{sp} } \mathord{\left/ {\vphantom {{\eta _{sp} } c}} \right. \kern-\nulldelimiterspace} c}} \right)}}{{dc}}\frac{1}{{[\eta ]^2 }} $\end{document}, is shown to be of increasing significance in polymer science as a molecular‐weight‐independent criterion of solvent power and as a parameter sensitive to various changes in polymer structure, such as long‐chain branching. Ideally, it is a dimensionless parameter, independent of molecular size, which arises only from the mutual hydrodynamic interaction of polymer molecules and depends, therefore, on the intrinsic flexibility of the polymer chain and on the polymer density in the coiled molecule. In real systems, however, other interactions may contribute, sometimes very significantly, to k′. For such real systems, the general expression:

is suggested. In ternary systems, polymer–polymer–solvent, ideal expressions for ηsp/c and k′ are developed, that for k′ being:

It is proposed that deviations from ideal behavior so defined are due to nonhydrodynamic polymer‐polymer interactions and might be used to detect and measure the strength of such interactions. Some preliminary data for the system polystyrene–poly(methyl methacrylate)–m‐xylene are presented and discussed.
Acid acceleration of epoxide condensations
Authors: Dearborn Elizabeth C. , Fuoss Raymond M. , White Alice F.
Published: April 2003

The addition of carboxylic acid to Epon 834‐phthalic anhydride resins accelerates the rate of cure. The maximum thermal yield point corresponds to reaction of all the epoxide groups in the ratio of two anhydride carbonyls to one epoxide oxygen or of one acid carbonyl to one epoxide oxygen. The initial presence of some secondary alcohol groups appears to be essential for initiation of reaction as suggested by Fisch and Hofmann. Carboxylic acids react directly with epoxide groups to produce secondary alcohols which in turn react with phthalic anhydride, regenerating carboxylic acid groups. Succinic acid gives a rapid cure (although not as fast as amines) to a resin with only slightly lowered thermal yield point, while benzoic acid depresses the yield point by about 15° because it acts as a chain‐stopper.
Mechanochemistry and ion exchange
Authors: Katchalsky A. , Zwick M.
Published: April 2003

The swelling behavior of crosslinked gels of polymethacrylic acid, partially or wholly neutralized by mixtures of sodium and barium hydroxide, is described. At high degrees of neutralization and high barium content there is a contractile region of rapid transition from a swollen to an unswollen state. A new type of contractile polyacid fiber made of Krilium and polyvinyl alcohol was developed. The force–elongation curves are given for these fibers at different degrees of neutralization with sodium and barium hydroxide in solutions containing sodium and barium chloride of various ionic strength. The dimensional changes caused by ion exchange can be utilized in a mechanochemical engine. An irreversible work cycle for such an engine is described in which the energy of mixing of mono‐ and divalent ions on polyelectrolyte fibers is partially converted into mechanical work.
Dye binding to high polymers
Authors: Oster Gerald
Published: April 2003

A number of examples are presented to show that cationic dyes bind to polymeric acids by simple electrostatic forces. Competitive binding for the substrate is illustrated by the addition of hydrogen ions, calcium ions, and streptomycin. Anionic binding to uncharged or to negatively charged substrates is attributed to hydrogen bonding with the carbonyl groups of the substrate. Van der Waals' forces also play an important role in the binding. Illustrations are given for the substrates, native serum albumin, denatured ovalbumin, polyvinylpyrrolidone, and water‐soluble urea‐formaldehyde resin. In the last‐named case the binding increases with increasing molecular weight of the substrate. A new fluorometric technique for following the binding of anions is described. The changes in spectral and photochemical properties which dyes undergo when bound are summarized.
Statistical thermodynamics of polyelectrolyte solutions. I. Activity coefficient of counter ion in salt‐free system
Authors: Kagawa Ikumi , Nagasawa Mitsuru
Published: April 2003

The authors investigated theoretically the activity coefficient of counter ion in the salt‐free polyelectrolyte solutions, by stressing the interionic interaction between the macro ion and counter ion. Assuming the Boltzmann distribution for the polyelectrolyte system and proposing a new linear approximation, the Poisson‐Boltzmann equation was solved for a model of spherical rigid macro ion, and then the free energy of the system was calculated by means of the charging‐up procedure. Applying this theory to the experimental data of activity coefficient of silver ion in the silver carboxymethyl cellulose solutions, the size of macro ion was computed, and the results are discussed from a purely theoretical standpoint. Thus, the authors have succeeded in giving a valid insight into the correlation between polyelectrolyte and simple electrolyte solutions as well as into some peculiar features of polyelectrolyte solutions.
Reactions of methyl radicals and their applications to polymer chemistry
Authors: Szwarc M.
Published: April 2003

An experimental method has been developed for determining the relative reactivities of various aromatic and olefinic compounds toward methyl radicals. The reaction in question may be represented by the equation CH3 + A → CH3. A, where A denotes an aromatic or olefinic molecule. By these means the reactivities of various vinyl monomers, inhibitors (such as quinones, nitro compounds, etc.), and aromatic hydrocarbons were determined on the same relative scale. The method can be utilized also for deriving the relative chain transfer data (for methyl radicals). A relationship between reactivity and singlet‐triple excitation energy has been demonstrated and explained in terms of energy diagram. The problem of efficiency of initiators is discussed in some details.
The polymerization of sulfur
Authors: Fairbrother Fred , Gee Geoffrey , Merrall G. T.
Published: April 2003

A previous analysis of the polymerization of liquid sulfur has been revised to take account of specific heat data now available and some new experimental evidence presented here. It is confirmed that liquid sulfur is essentially an equilibrium mixture of S8 rings and long free radical chains. The heat of polymerization (S8 → inifinite chain) is estimated as 3180 cal./mole of S8 at 432°K., where polymerization sets in rather abruptly; the corresponding entropy of polymerization is +7.4 cal. mole−1 deg.−1. There is evidence for the presence of rings of more than 8 atoms; the concentration of these reaches a maximum of ca. 1% in the neighborhood of the critical polymerization temperature (432°K.). Magnetic susceptibility measurements place an upper limit of 2 × 10−2 moles l.−1 on the free radical concentration. From this and other lines of evidence it is concluded that the heat of scission of sulfur chains does not exceed 35 kcal., and an explanation is put forward.
Contribution à la cinétique de polymérisation dans les milieux précipitants
Authors: Magat Michel
Published: April 2003

Une tentative est faite d'utiliser pour la description de la polymérisation en milieu précipitant le schéma cinétique habituel (amorçage, propagation, terminaison mutuelle), mais en admettant que l'état quasi‐stationnaire n'est pas atteint au début de la réaction. Le système d'équations différentielles pu être résolu pour certains cas: concentration constante de catalyseur, concentration décroissante selon une loi cinétique de premier ordre, etc…. Une méthode d'approximation est proposée pour traiter les cas où il y a accumulation du catalyseur dans la phase monomère par suite de son insolubilité dans le polymère. Les formules obtenues permettent de rendre compte de la polymérisation en masse du chlorure de vinyle, à différentes températures et à différentes concentrations du catalyseur (peroxyde de benzoyle), et ceci aussi bien pour des expériences à faibles degrés de conversion que pour des expériences poussées à des degrés de conversion élevés. Les constantes kp/kt et (kaA0kt)−1/2, déterminées à différenctes températures correspondent à des énergies d'activation E − E = 5,2 kcal., E + E = 29,6 kcal. Cette dernière valeur indique que l'énergie d'activation de terminaison n'est pas très élevée et que le ralentissement de terminaison observé est dû à une diminution du facteur de fréquence. Les mêmes formules ont été utilisées pour le cas de polymérisation du chlorure de vinylidène. Dans ce cas il a été possible de calculer les valeurs absolues des constantes de vitesse de terminaison et de propagation qui sont très sensiblement plus faibles que dans le cas de polymérisation en milieu homogène. Certaines difficultés persistent, qui amènent à penser que la théorie n'est pas complète.
Turbidimetric titration of block polymer solutions
Authors: Melville H. W. , Stead B. D.
Published: April 2003

The turbidimetric titration method, used previously to determine molecular weight distributions in polymers, has been used for the qualitative examination of various polymers: mixtures containing block copolymer (styrene‐methyl methacrylate or vinyl acetate‐methyl methacrylate), polystyrenes prepared in branching studies, and commercially prepared polystyrenes. The method is a sensitive and rapid one and is suitable for the examination of very small quantities of polymer. A semiautomatic titration apparatus is also described.
Copolymers in dilute solution. I. Preliminary results for styrene‐methyl methacrylate
Authors: Stockmayer W. H. , Moore L. D. , Fixman M. , Epstein B. N.
Published: April 2003

The dilute solution properties of copolymers are briefly discussed in relation to those of the parent homopolymers. It is shown that copolymer molecules are usually more expanded in solution than would be expected from the averaged behavior of the pure polymers, because of repulsive interactions between the unlike monomer units. A thermodynamic parameter χAB characterizing these interactions can be derived from measurements of the dilute solution properties of copolymers. In favorable cases this parameter can be independently evaluated from studies of ternary systems composed of the two parent homopolymers and a solvent, thus allowing prediction of the behavior of the copolymer. Light scattering and viscosity measurements on fractions of approximately equimolal copolymers of styrene and methyl methacrylate are presented and analyzed. The values of χAB deduced from the results in two solvents agree satisfactorily with each other, but are somewhat larger than those earlier obtained from measurements on ternary systems.
Die ubertragungskonstante von polymethylmethacrylat bei der polymerisation von methylmethacrylat und styrol
Authors: Schulz G. V. , Henrici G. , Olivé S.
Published: April 2003

Die Übertragungskonstante von Polymethylmethacrylat hei der Polymerisation von Methylmethacrylat hzw. Styrol wird dadurch bestimmt, dass man Polymeres von sehr kleiner Kettenlänge dem polymerisierenden Stoff zusetzt. Das zugesetzte α‐Polymere beeinflusst nicht die Bruttogeschwindigkeit, setzt aber den Polymerisationsgrad des entstehenden Polymeren herab. Für diesen Vorgang gelten dieselben Gleichungen wie für niedermolekulare Regler. Die Übertragungskonstante von Polymethacrylat setzt sich aus zwei Anteilen zusammen, welche den Mittelgruppen und einer Endgruppe entsprechen. Die wirksame Endgruppe ist hei der Disproportionierung entstanden. Polystyrol zeigt keinen Endgruppeneffekt, da das Kettenwachstum durch Kombination beendet wird. Aus den gemessenen Übertragungskonstanten kann der Grad der Verzweigung bei Polymethacrylaten und Polystyrolen abgeschätzt werden.
The extension of polystyrene chains: Dependence on molecular weight and solvent
Authors: Notley N. T. , Debye P. J. W.
Published: April 2003

The relation between molecular size and weight for polystyrene in cyclohexane at 34, 43, and 57°C. and toluene at 20°C. has been determined by a light scattering method. For the molecular weight range, half‐million to five million, the data suggest a linear relationship:

L2 = κ (M − b)
where κ and b are parameters which have their higher values in better solvents.
The crystal structure of polycaproamide: Nylon 6
Authors: Holmes D. R. , Bunn C. W. , Smith D. J.
Published: April 2003

The crystal structure of nylon 6 (NH (CH2)5CO)p has been determined by interpretation of the x‐ray diffraction patterns given by drawn, rolled fibers. The determination was part of a program to investigate the relation between structure and physical properties, in particular melting point. Nylon 6 melts 50°C. lower than its isomer nylon 66 (NH (CH2)6NH·CO (CH2)4CO)p; it had been suggested that this was due to deficient hydrogen‐bond formation in nylon 6 crystallites. The unit cell contains eight chemical units (NH (CH2)5CO) and is monoclinic with a = 9.56 A., b = 17.24 A., c = 8.01 A., and β = 671/2°. Calculated density = 1.23. Observed density for a drawn monofilament = 1.16. The structure consists of planar chains of CH2 groups and amide groups tilted 7° from the (001) plane. Alternate chains in this plane are oppositely directed, an arrangement which allows all hydrogen bonds to be made perfectly. The hydrogen‐bonded sheets of atoms are packed in an “up‐and‐down” staggered configuration along the c‐axis. Distances between atoms in neighboring molecules are all normal van der Waals contact distances. It appears, from a general survey of polyamide melting points published elsewhere, that the determining factor is the number of CH2 groups between the amide “anchor points”—polymers with odd numbers of CH2 groups melt lower than those with even numbers. The present work shows that the odd number of CH2 groups in this polymer does not lead to deficient hydrogenbond formation, and that the lower melting point of nylon 6 as compared with nylon 66 must be ascribed to some other cause, possibly connected with the propagation of vibrations along odd‐numbered chain segments.
Determination of the tensile strength of gels
Authors: Ben‐Arie Michael M.
Published: April 2003

A method has been devised and an apparatus constructed for measuring the tensile strength of viscoelastic gels. The method consists of extruding the gel vertically through a nozzle of diameter of 2–14 mm. and weighing the gel‐column falling by its own weight. The weight of the column divided by the area of the nozzle gives the value of the tensile strength. The latter lies for Napalm gels of 2–6% Napalm in gasoline within the limits of 1.5–8 g./cm.2. The so determined tensile strength depends on the extrusion velocity, but is independent of the area and other dimensions of the nozzle; it is also independent of the driving pressure. The functional dependence of the tensile strength on the extrusion velocity and the form of this function have been established by a numerical approximation. The tensile strength of viscoelastic fluids has been shown to depend on the viscosity coefficient and on Young's modulus. It follows that thixotropy and work‐hardening are interrelated phenomena.
Dielectric constant–strain coefficient of polystyrene and lucite at 3.2 centimeters
Authors: Horton C. W. , Rogers R. G.
Published: April 2003

Two experimental procedures have been used to measure the effect of elastic strains on the dielectric constants of polystyrene and Lucite. In the first experiment the dielectric sample was placed in a section of a standard X‐band wave guide. Stresses were applied parallel and perpendicular to the electric field. In the second experiment the dielectric sample was placed in a resonant cavity. The cavity was excited in the TE011 mode and the applied stress was perpendicular to the electric vector. The data are presented in terms of a so‐called dielectric constant‐strain coefficient, β, which is defined as the ratio of the fractional change in the dielectric constant to the compressional strain of the sample. When these values are converted to the customary stress‐“optical” coefficients, one obtains C = 6 × 10−12 cm.2/dyne for polystyrene and Lucite.
A semimicro dilution viscometer
Authors: Hart Victor E.
Published: April 2003

An accurate semimicro capillary viscometer is described in which dilutions can be made. A glass valve assembly eliminates evaporation and makes operation convenient. Techniques for semimicro work are described and specifications are given for an instrument suitable for intrinsic viscosity determinations with 1 milliliter of solution.
A graphic method for single‐point determination of intrinsic viscosity
Authors: Hart Victor E.
Published: April 2003

For a given polymer‐good‐solvent system at a fixed temperature, the product of intrinsic viscosity and concentration is a unique function of specific viscosity alone up to high values of specific viscosity. This permits a single parametric curve to be drawn from experimental data; thereafter, accurate calculation of intrinsic viscosity from the results of a single specific viscosity measurement becomes possible with the aid of a convenient equation.
Bis‐type modifiers in polymerization. I. Behavior of various disulfides in bulk styrene polymerization
Authors: Pierson R. M. , Costanza A. J. , Weinstein A. H.
Published: April 2003

Modifiers with bis‐type structures are of interest as a means for conferring reactive groups onto the highest possible fraction of polymer chain ends. Various disulfides and other bis‐type compounds—some with reactive groups attached—were compared as to their effectiveness as modifiers in low conversion bulk styrene polymerizations and studies made of their mechanism of cleavage. Alkyl disulfides of primary thiols had transfer constants too low to be of much interest for this work, even when substituted at carbons near the sulfur‐sulfur bond. Aryl disulfides proved to have much higher transfer constants, and substitution on each ring with appropriate groups offered a means both of increasing the transfer constant and of incorporating desired groups.

It has been shown quite conclusively that aryl disulfides cleave so as to confer one‐half the molecules onto each end of the polymer. This was demonstrated by analyzing the end group concentrations of styrene polymers of wide molecular weight range which contained various types of end groups—carboxyl, amino, naphthyl, and benzothiazyl—and comparing, wherever possible, with polymers modified with thiols containing similar groups.

Polymerizations carried out at 25, 50, and 75°C. with certain of the bis‐type compounds and with a normal and a tertiary mercaptan showed that activation energies are very slight if the transfer constant is high, and begin to reach significant levels only at low levels of transfer constant.
Structural analysis of novolacs
Authors: Boelhouwer C. , Waterman H. I. , Wijnands P. H. W.
Published: April 2003

The structure of certain novolacs, prepared by polycondensation of formaldehyde with phenol, p‐cresol, and m‐cresol respectively, was investigated. The novolacs were transformed into saturated hydrocarbons, thus expelling the oxygen, by a relatively mild high pressure hydrogenation (300°C., 250 atm.) using 100% by weight of a nickelcopper on kieselguhr catalyst. It can be expected that this treatment does not alter the structural frame of the molecules. From ultimate analysis and physical constants of the hydrocarbons, conclusions were made as to the structure of the novolacs. They are linear thermoplasts; no “extra” rings are present.