bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mechanism of chain initiation and chain transfer in the polymerization of vinylpyridine
Authors: Dannley Ralph L. , Schufle Joseph A. , Cohen Irwin , Chambers James R. 
Published: April 2003

Abstract(1) Polymerization of 2‐vinylpyridine in p‐chlorotoluene solution produced a polymer which, when oxidized with potassium permanganate in dilute sulfuric acid, gave no chlorophthalic acid, but a 35.7% yield of p‐chlorobenzoic acid (based upon the halogen content of the polymer). Therefore, incorporation of the aromatic groups in the polymer, probably in the step of chain transfer, occurred by reaction with the side chain and not the nucleus of the p‐chlorotoluene. The absence of chlorophthalic acid was significant, for a similar oxidation of α‐(p‐methylbenzyl)pyridine gave a 3% yield of terephthalic acid as well as a 23% yield of 2‐(4‐carboxybenzoyl)pyridine. (2) Permanganate oxidation of this same polymer in 25% sulfuric acid gave a 27% yield of p‐chlorobenzoic acid. This represents the maximum yield of halobenzoic acid to be expected from a polyvinylpyridine containing trace quantities of halophenyl and pyridine nuclei separated by a chain of two or more carbon atoms. In contrast, similar oxidations in 25% sulfuric acid of α‐(p‐bromobenzyl)‐ and α‐(p‐chlorobenzyl)pyridine gave much smaller yields (16 and 14%, respectively) of the corresponding halobenzoic acids. In concentrated acid, the heterocyclic rings form stable salts and oxidation of the benzylpyridine type structure leads to preferential cleavage of the benzene nucleus. (3) Initiation of the polymerization of 2‐vinylpyridine with N‐nitroso‐p‐bromoacetanilide formed a polymer which, upon oxidation with potassium permanganate in 25% sulfuric acid, gave a 31% (average) yield of p‐bromobenzoic acid. Since this yield is that expected from a polymer in which pyridine and bromobenzene rings are separated by a chain of two or more carbon atoms, beta carbon atoms addition in chain initiation by a bromophenyl radical is substantiated. (4) Polymerization of 2‐vinylpyridine in bromobenzene solution provided a polymer which, upon oxidation with permanaganate in 25% sulfuric acid, gave only a 6% yield of bromobenzoic acid, corresponding to a bromobenzylpyridine structure in the polymer. Reasons are given why this data supports but does not prove the hypothesis that chain transfer consists of substitution in the bromobenzene nucleus by a polymer radical possessing a 2‐pyridylmethyl structure.
Raman spectra of monomeric and polymeric allyl diglycol carbonate
Authors: Jeppesen Myron A. 
Published: April 2003

AbstractThe Raman spectra of monomeric and polymeric allyl diglycol carbonate (CR‐39) have been photographed. A partial frequency assignment has been made on the basis of a comparison of the two spectra, depolarization measurements, and reference to published spectra of related compounds. The spectrum of the polymer indicated almost complete polymerization of the unsaturated aliphatic double bonds. A channelled comparison spectrum was used, and its advantages noted.
The melting range of semicrystalline polymers and copolymers
Authors: Dole Malcolm 
Published: April 2003

AbstractAn equation is derived for the weight‐average crystallite length of crystallizable sequences between noncrystallizing copolymer units. This expression is used to estimate the depression of the melting point due to the subdivision of the crystalline regions into small crystallites. An explanation is given for the failure of the value of the heat of fusion calculated from the equation relating the freezing point lowering to the mole fraction to agree with observed values.
Copolymerizations of vinyl silanes
Authors: Thompson B. R. 
Published: April 2003

AbstractA brief experimental investigation was made of the copolymerization of twelve alkoxysilanes with monochlorostyrene, vinyl chloride, and acrylonitrile. These new monomers include vinyltrimethoxy‐, vinyltriethoxy‐, vinyltriisoproxy‐, vinylmethyldiethoxy‐, vinylethyldiethoxy‐, and vinylphenyldiethoxy‐silanes as well as allyl‐, propenyl‐, 2‐butenyl‐, Δ3‐cyclohexenyl‐, 6‐triethoxysilylbicyclo [2.2.1]heptane‐2, and α‐chlorovinyl‐triethoxysilanes. No copolymerization took place with monochlorostyrene. In the copolymerizations with vinyl chloride, and with acrylonitrile, the reactivity ratio r2 was assumed to be zero and the value of r1 determined.
Polyethyl methacrylate. II. Dilute solution properties by viscosity and light scattering
Authors: Chinai Suresh N. , Samuels Robert J. 
Published: April 2003

AbstractA polyethyl methacrylate polymer, prepared by the emulsion technique, was fractionated three times to obtain ten fractions. The intrinsic viscosity‐molecular weight relations were established in an ideal and in a nonideal solvent at 23°C. Light scattering measurements giving polymer dimensions were compared with the viscosity theories advanced by Debye‐Bueche, Kirkwood‐Riseman, and Flory‐Fox. The calculated values of the effective bond length b for polymethyl methacrylate and polyethyl methacrylate show that polymethyl methacrylate chain has greater hindrance to rotation than the polyethyl methacrylate chain. The results are explained by consideration of the free volume occupied by the solvent molecules.
Light scattering and viscosity studies of polyvinyl acetate solutions
Authors: Varadaiah V. V. 
Published: April 2003

AbstractA light scattering photoelectric photometer was built and calibrated by a narrow fraction of polystyrene for which the molecular weight was assigned by the viscosity method. The instrument was used to determine the molecular weights of polyvinyl acetate fractions. The light scattering molecular weights of the polyvinyl acetates, up to a value of 477,000, agreed with those obtained from viscosity data employing the Nakajima equation: [η] = 8.91 × 10−3 × P0.62, where [η] is the intrinsic viscosity in benzene and P is the degree of polymerization. k′ and μ values lie in the expected ranges. The rootmean‐square end‐to‐end distances of the polyvinyl acetate molecules determined by the dissymmetry method are found to be much smaller than those calculated by Fox‐Flory relation from viscosity data.
An independent measurement of the amorphous content of polymers
Authors: Miller R. G. J. , Willis H. A. 
Published: April 2003

AbstractAttempts have been made, particularly by American workers, to exploit differences in crystalline and amorphous polymer spectra to determine crystalline/amorphous ratios. In most published work authors have been forced to rely on calibration by other methods, especially density. They have justified the use of the spectroscopic method principally on the grounds of speed in obtaining results. We propose a spectroscopic method, applicable to a number of polymers, which is entirely independent of other measurements. We are thus able to compare our results with those obtained by other methods and have in some cases been able to draw useful conclusions from apparent anomalies. Our method depends upon measurement of pure amorphous bands. We consider these to arise from the multiplicity of rotational isomers present in the amorphous phase. The pure amorphous spectrum of many polymers can be obtained, and by this means an absolute calibration of amorphous content is possible. Crystalline bands cannot be so calibrated; they are dangerous to use quantitatively, although superficially more attractive because of their sharpness. The application of the method to some common polymers including polythene, polyethylene terephthalate, and polytetrafluorethylene is described; the results are compared with values obtained by x‐ray and density methods.
Emulsion polymerization of chloroprene. II. Molecular weights
Authors: Morton Maurice , Piirma Irja 
Published: April 2003

AbstractThe molecular weights of emulsion polychloroprenes, prepared at four different temperatures in the presence and absence of a suitable mercaptan chain‐transfer agents, have been studied. The particular mercaptan used, a tertiary dodecyl type, was found to disappear at the relatively slow rate, which was first‐order up to high conversions. This permitted the preparation of polymer having a relatively uniform intrinsic viscosity up to high conversions. However, under certain conditions, the crosslinking reaction was found to give rise to the usual peaks in the viscosity–conversion curves. These curves differed from those of other dienes studied, in that the heights of the maxima depended not only on polymerization temperature but also on the mercaptan charge. This anomaly could be accounted for by the possibility of more than one mechanism of crosslinking. The above behavior made it impossible to obtain a quantitative measures of the crosslinking rate. However, observations of the postpolymerization changes experienced by this polymer lead to the conclusion that it has a high crosslinking rate.
A light scattering study of corn amylopectin and its beta‐amylase limit dextrin
Authors: Stacy Carl J. , Foster Joseph F. 
Published: April 2003

AbstractThe degree of dispersion of a corn amylopectin and its ß‐amylase limit dextrin was studied in 1 N alkali, anhydrous ethylenediamine, ethylenediamine hydrate, formamide, and water by means of measurements of the concentration and angular dependence of scattered light. It was found that the degree of dispersion in the first three solvents is essentially the same for both preparations. The molecular weight of the amylopectin and limit dextrin are 80 million and 29 million, respectively. This result is in agreement within experimental error with the ratio of molecular weights to be expected on the basis of the known degree of degradation by ß‐amylase, and supports the view that essentially molecular dispersions were obtained. The agreement further indicates that the molecular weight distributions of the amylopectin and limit dextrin are similar in form. With this assumption and the radii of gyration of the materials, 2090 and 1340 A., it is concluded that the simplest model consistent with the data is a spherically symmetrical distribution of segments with segment density decreasing with r.
Linear phenol‐formaldehyde polymers—condensation of p‐chlorophenol with formaldehyde
Authors: Burke W. J. , Craven W. E. , Rosenthal Alex , Ruetman S. H. , Stephens C. W. , Weatherbee Carl 
Published: April 2003

AbstractHigh molecular linear polymers were prepared by the condensation of p‐chlorophenol with formaldehyde at 150°C. for 24 hours in a closed system with bis(2‐ethoxyethyl) ether as solvent and p‐toluenesulfonic acid as catalyst. The importance of reaction variables including temperature, time, solvent, catalyst, and concentration and ratio of reactants was studied. Polymers of this type were also prepared by the polymerization of 4‐chloro‐2‐hydroxymethylphenol and by the condensation of p‐chlorophenol with 2,6‐bis(hydroxymethyl)‐4‐chlorophenol. Data obtained on the polymers from the three independent routes indicated the presence of methylene bridges between the ortho position of the p‐chlorophenol residues. The polymers were soluble in N,N‐dimethyl formamide and reacted readily with acetic anhydride to form the corresponding acetylated derivatives.
Viscoelastic behavior of polyisobutylene under constant rates of elongation
Authors: Smith Thor L. 
Published: April 2003

AbstractThe use of stress‐strain curves to characterize the linear viscoelastic properties of rubberlike materials is discussed. Tensile stress‐strain curves for a high molecular polyisobutylene were measured at ten temperatures between −54 and 85°C. and at strain rates between 0.104 and 0.104 × 10−3 sec.−1. At a single temperature, the data superpose on a double logarithmic plot of stress divided by strain rate against strain divided by strain rate. By superposing data obtained at different temperatures, the temperature dependence of viscosity was obtained. All data for elongation up to 100% were combined to give a single reduced stress‐strain curve, which extends over ten decades of reduced time. From the reduced curve, the stress‐relaxation modulus was calculated and found to agree satisfactorily with published data.
Ermittlung der äusseren Abmessungen statistisch geknäuelter Fadenmoleküle durch Ausmessung makroskopischer Modelle
Authors: Hoops Irmgard , Kuhn Hans , Huber Walter , Eckert Lieselotte 
Published: April 2003

AbstractEs wurden 362 Kreissegmentmodelle statistisch geknäuelter Fadenmoleküle hergestellt und daran die Parameter h (Abstand zwischen Fadenanfangs‐ und ‐endpunkt), R (Abstand zwischen Fadenanfangspunkt und demjenigen Fadenelement, das von allen den grössten Abstand vom Anfangspunkt besitzt), H1 (Maximalabmessung des Knäuels), H2 (grösste senkrecht zu H1 gemessene Querabmessung des Knäuels), H3 (grösste Abmessung des Knäuels senkrecht zu H1 und H2) gemessen. Die auf Grund dieser Messungen sich ergebenden Verteilungsfunktionen W(H1), W(H2), W(H3), die bisher ungenügend genau bekannt waren, werden angegeben. Zwischen den Mittelwerten der erwähnten Parameter werden die Beziehungen \documentclass{article}\pagestyle{empty}\begin{document}$\bar H_1 = 1,74\bar H_2 = 2,72\bar H_3 = 1,36\bar h;(\bar H_1^2)^{1/2} = 1,78(\bar H_2^2)^{1/2} = 2,77(\bar H_3^2)^{1/2} = 1,41\bar h = 1,30(\bar h^2)^{1/2}$\end{document} gefunden. Daraus folgt, dass dem Knäuel im Mittel ein Achsenverhältnis H1:H2:H3 = 2,72:1,56:1 zuzuschreiben ist. Es wird untersucht, wie häufig bei gegebenen Werten von H1 die verschiedenen Werte von H2, H3, h und R vorkommen, wieweit also Beziehungen zwischen diesen Parametern bestehen. Man findet, dass Konstellationen, in welchen das eine Ende von H1 (Verbindungsstrecke zwischen den beiden am weitesten auseinanderliegenden Fadenelementen) mit dem Fadenanfangs‐ oder ‐endpunkt zusammenfällt, relativ häufig vorkommen (bei Modellen mit 20 Vorzugselementen beispielsweise in 37% aller Fälle).
Some factors involved in the preparation of uniform particle size latexes
Authors: Vanderhoff J. W. , Vitkuske J. F. , Bradford E. B. , Alfrey T. 
Published: April 2003

AbstractSome factors involved in the preparation of monodisperse polymer latexes by seeded emulsion polymerization are discussed. In this technique monomer and catalyst are added to a previously prepared latex; during the subsequent polymerization these seed particles grow to a larger size. A mathematical analysis has been developed relating the particle volume increase to particle size as a power function. Competitive particle growth has been determined experimentally by polymerizing monomer in a seed latex comprised of a mixture of two monodisperse latexes of different sizes. In these experiments the diameters of the smaller particles increase at a slightly greater rate than those of the larger ones. Therefore the final particle size distribution is narrower than that of the seed latex. In these growth experiments the concentration of emulsifier is also important. An illustrative example shows that excessive emulsifier initiates new particles and insufficient emulsifier causes coagulum.
Effect of urea on the viscosity of deoxyribonucleic acid solutions
Authors: Conway B. E. 
Published: April 2003

AbstractThe effect of urea and sodium chloride on the viscosity of DNA has been examined at very low concentrations and rates of shear in a Couette viscometer. An increase of apparent intrinsic viscosity occurs in urea, but at higher concentrations of the polymer a reduction of viscosity is observed. When treated with urea, the intrinsic viscosity of the nucleic acid becomes lowered by sodium chloride. The results are consistent with a dimeric hydrogen‐bonded structure of the DNA molecule, which undergoes scission in the presence of urea to form more flexible fragments.
Emulsion polymerization of triallyl phosphate with halomethanes
Authors: Frick J. G. , Weaver J. W. , Arceneaux Richard L. , Stansbury Mack F. 
Published: April 2003

AbstractTrially phosphate has been polymerized in emulsion by itself and with four halogenated methanes: carbon tetrabromide, bromoform, bromotrichloromethane, and carbon tetrachloride. Of the four halomethanes, carbon tetrachloride enters telomer formation only to a slight extent, and bromoform and carbon tetrabromide enter to the greatest extent. In most cases a product consisting of two distinct fractions was formed, a solid‐insoluble polymer, and a liquid‐soluble polymer. The latter is of only a low degree of polymerization, ranging from 1.0 to 2.3 phosphate units. In the course of the reaction, the soluble fraction is formed first and then is partially converted to the insoluble fraction by crosslinking. The polymerization of trially phosphate with bromoform received the most study. In this case the ratio of insoluble to soluble fraction can be changed by varying the amount of initiator and the ratio of bromoform to phosphate. A molar ratio of bromoform to trially phosphate greater than 2.0 yields only monomeric addition products. By the proper choice of conditions a very stable emulsion of a polymer containing phosphorus and bromine can be obtained. This emulsion is suitable for direct application to cotton textiles in order to produce flame‐resistant fabrics.
The scattering of light from thin polymer films. II. Scattering from polyethylene
Authors: Keane John J. , Stein Richard S. 
Published: April 2003

AbstractPolyethylene may be characterized by use of the light scattering technique applied to the solid polymer. The treatment of Debye and Bueche allows one to assign numerical values to this characterization in the form of two parameters, 〈η2〉, the mean square dielectric constant deviation and a size parameter, α, associated with a spacing within the polyethylene microstructure. This spacing has not as yet been definitely identified with regard to the polyethylene crystallites or spherulites. The numerical values obtained of 2000–3000 A. are too large to be crystal edges and too small to be spherulite radii. The magnitude of the mean square dielectric constant deviation from the average should be associated with the amount of inhomogeneity in the solid, that is, the amount of crystallinity. No direct relation has been found in this work, however, between per cent crystallinity as measured by density and the value of ∠η2〉. The study of 〈η2〉 through a melting and cooling cycle shows a hysteresis effect which is dependent on rate of cooling from the molten state. The effect of heating polyethylene on the value of 〈η2〉 parallels a curve of per cent crystallinity vs. temperature. When the sample is cooled there is a point of maximum scattered intensity and maximum 〈η2〉 at about 106.5°C. Study of the value of α in the melting and cooling process shows it is essentially a constant at all temperatures under equilibrium conditions. If α is studied as a function of time after rapid cooling from the melt to 106.5°C., it is found to maximize after about 20 minutes. This implies that there is a definite spacing between crystalline regions in the spherulite and that, once this spacing is reached, further aggregation can occur only by more crystalline material attaching itself to the periphery of the spherulite with the same spacing or consolidation of existing crystalline regions.
Electrical analogs for viscoelastic systems
Authors: Gross Bernhard 
Published: April 2003

AbstractWith the use of well‐known developments of electric circuit theory it can be shown that a correspondence exists between mechanical relaxation systems and electrical reactance systems. To each line of the mechanical relaxation spectrum corresponds a resonance line, to each line of the retardation spectrum an antiresonance line of the electrical system. Transformation equations between these systems are established. The reactance system can be used as an analog computer. Since resonance and antiresonance frequencies can be determined with conventional a.c. methods, a direct measurement of the spectra becomes possible. Knowledge of the spectra enables one to formulate analytic expressions for viscoelastic functions. The method applies to system with lumped and with continuously distributed parameters, like transmission lines. Dissipation in the circuit elements of the reactance system can be taken into account quantitatively. Other results, which are immediately obtained, are: all viscoelastic systems can be represented by ladder structures. Lines of the retardation spectrum alternate with lines of the relaxation spectrum.
Electron‐exchange polymers. VII. The ion‐exchange and electron‐exchange behavior of hydrophilic hydroquinone copolymers
Authors: Luttinger Lionel , Cassidy Harold G. 
Published: April 2003

AbstractCountercurrent experiments on two types of sulfonated, water‐swellable, ion‐and electron‐exchange resins were performed. One type contained as commonomers vinyl‐hydroquinone, alpha‐methylstyrene, and divinylbenzene. The other type contained vinylpyridine in addition to the other comonomers. Both types demonstrated rapid, reversible cation exchange with satisfactory capacity, and reversible, slow electron exchange with acid KI and acid Br2. The electron‐exchange capacity was high. The reactions were reversible up to a pH of at least 4.7. At high pH (8.5), slow, irreversible changes occurred. Even at low pH, the resins were gradually broken down by such oxidants as ceric and ferric ions. The cation‐ and electron‐exchange equilibria were shown to be without appreciable effect on one another. Ferricyanide failed to oxidize the reduced form of such resins quantitatively, presumably because of its low potential. Interpretation of the behavior of the resin‐containing vinylpyridine was more difficult, due to the increased complexity, but nevertheless a reasonable amount of base exchange, as well as acid exchange, was demonstrated. Some possible improvements in the stability of these substances at high pH and toward other oxidants, are proposed.
Measurement of viscosity‐average molecular weight of polymer solutions of unknown concentration
Authors: Frisch H. L. , Yeh Si Jung 
Published: April 2003

AbstractIn a number of contexts it is of interest to determine the viscosity‐average molecular weight of a polymer solution whose concentration is not known. Certain ways of ac‐complishing this can be shown to reduce to the comparison of measurements of the specific viscosity of equiconcentrated polymer solutions in two different solvents. The limits of precision of this technique are indicated and checked experimentally on a number of solutions of known composition of mixtures of polystyrene fractions. The agreement between the found viscosity‐average molecular weight and that calculated from the known composition of the polymer fraction mixture is satisfactory.
Effect of field intensity and quantity of electricity upon counterion fixation by polyelectrolytes
Authors: Wall F. T. , Terayama Hiroshi , Techakumpuch Sunt 
Published: April 2003

AbstractNumerous transference experiments on polyelectrolytes have demonstrated that an appreciable fraction of the counterions move during electrolysis with the polyelectrolyte ion of opposite charge. The present studies were carried out to determine the effect of field intensity and the extent of electrolysis on the apparent degree of counterion fixation. It is found that the degree of ion binding depends upon the applied field and that up to a certain point the association diminishes with increasing field. The results are interpreted to mean that the ions are not all held equally firmly. Some ions are held loosely and move as a kind of atmosphere with the polymer ions only when the applied field is small. Other ions are firmly held and are carried along even in the presence of a strong field which would tend to cause separation of the oppositely charged ions. Using polyacrylic acid partially neutralized with sodium hydroxide, it is observed that from 10 to 20% of the ions that are bound are “loosely” bound and hence not carried along under strong fields. As might be expected, the different degrees of binding are observed to be functions of the degree of neutralization.