bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lattice model calculation of the configurational entropy change for athermal mixtures
Authors: Krigbaum W. R. 
Published: April 2003

AbstractThe lattice model treatment of athermal mixtures is reexamined by considering a two step process in which a growing chain forms an interference with a completed molecule. The expectancy, f, that an interference will arise is given by the product of the respective probabilities, P, and Q, that each step will occur. For low solute concentrations, the result is nearly the same as a revised form of the equation derived in various ways by Huggins, Miller, Orr, and Guggenheim. The same result is obtained for linear, bent, or branched molecules, but only so long as no ring‐forming intramolecular contacts exist. Dilute solutions of coiling polymer molecules require special treatment, due to a variable number of intramolecular 2‐2 contacts that depends upon the average molecular configuration. Branching, through its effect on molecular configuration, will after the dilute solution properties. The effect of branching and intramolecular contacts should become less important as the polymer concentration is increased. As the volume fraction of solute is increased, both of the probabilities, P and Q, become rapidly varying functions of this variable. An approximate calculation based on the two‐step encounter process yields values for f nearly equal to the average expectancy f̄ that a randomly selected site will be occupied. The latter was empolyed in the treatment of Flory. Thus, the refinements introduced by Huggins and others are only applicable to dilute solutions of noncoiling molecules. This furnishes an explanation for the observation that the proposed refinements do not improve the agreement with experiment shown by the simpler expression due to Flory.
Kinetics and heats of copolymerization of acrylonitrile and methyl methacrylate
Authors: Baxendale J. H. , Madaras G. W. 
Published: April 2003

AbstractMethyl methacrylate and acrylonitrile monomers have been copolymerized in aqueous solution and at room temperature, in the presence of an emulsifying agent, using the redox catalyst, ferrous ions, and hydrogen peroxide. The copolymer latex resembles that of polymethyl methacrylate similarly prepared. The rate and extent of conversion of monomers to copolymer were obtained by independent estimations of both monomers in the reaction mixture. Heats of copolymerization have been measured using a wide ratio of initial methyl methacrylate and acrylonitrile concentrations. The values lie between those of the respective homopolymerizations. The results are discussed in terms of the steric hindrances in a polymer composed entirely of a 1,1‐disubstituted monomer being reduced by the incorporation of a monosubstituted monomer into the chain.
Determination of degree of crosslinking in natural rubber vulcanizates. Part I
Authors: Mullins L. 
Published: April 2003

AbstractThis paper examines the relationship between the stress–strain properties of highly swollen natural rubber vulcanizates and their equilibrium volume swelling. It is shown that the empirical relationship obtained can be described equally well by either the Flory‐Huggins equation or the Flory modification of this equation, and values of the interaction constant μ for natural rubber in decane are determined. Observed differences in the values of μ obtained for sulfur and peroxide vulcanizates are interpreted in terms of the diluent effect of nonrubber constituents in the former. The effect of the initial molecular weight of the unmasticated rubber on these physical properties is examined and an empirical correction making allowance for chain segments terminated by a crosslink at only one end is obtained. The correction is larger than that derived by previous workers and possible sources of the observed differences are discussed. It is considered that internally self‐consistent estimates of the degree of crosslinking of natural rubber vulcanizates may be obtained using the methods developed.
An investigation of the theory of rubber elasticity using irradiated polydimethylsiloxanes
Authors: Bueche A. M. 
Published: April 2003

AbstractHigh‐energy electrons were used to crosslink a series of polydimethylsiloxanes. Equilibrium tension measurements at low elongations were used to determine the number of chains between crosslinks as given by the kinetic theory of elasticity. After a rapid increase at low radiation doses the number of chains was found to be proportional to the dose. The linear relationship between number of chains and dose, found at higher doses, extrapolated to zero dose, has a positive intercept. This intercept was independent of the initial molecular weight of the polymer and was taken to be a measure of the effect of the maximum number of permanent entanglements in this polymer. The dependence of the number‐average molecular weight of irradiated polydimethylsiloxane fluids on radiation dose was determined. The data were analyzed to find the efficiency of crosslink formation in this polymer. The number of chains between crosslinks produced by a given dose and determined by the kinetic theory was found to be only one‐half the number to be expected from the measurement of the molecular weights of the irradiated fluids.
Diffusion in concentrated polymer solutions. I. A. An interferometric micromethod for diffusion measurements. B. Diffusion of sucrose in solutions of polyvinylpyrrolidone
Authors: Nishijima Yasunori , Oster Gerald 
Published: April 2003

AbstractA simple micromethod for the measurement of diffusion coefficients has been developed. The diffusion cell is a wedge of two partially reflecting microscope slides and the liquids to be examined are placed in the wedge. Typical results for the diffusion of glycerol against water and 10% sucrose against water are shown. The method is applied to the measurement of the diffusion of sucrose in various concentrations of polyvinylpyrrolidone using samples of three different molecular weights. The local relative viscosity, as given by the ratio of the diffusion constant in water to that in the polymer solution, is nearly unity for low concentrations of polymer but above a critical concentration rises to a value that is independent of molecular weight of the sample. The lower the molecular weight, the higher is the critical concentration and the more abruptly is the rise in local viscosity with polymer concentration. These results are explainable in terms of a random coil model if it is assumed that the critical concentration is reached when the molecules overlap to a small extent. The rise in local viscosity is attributed to an entanglement of the chain segments resulting finally in a loss of identity of the individual polymer molecules. Applications of these results to a theory of wet spinning of fibers are indicated.
Variation of photoelastic behavior with temperature for some polymers
Authors: Kawata Kozo 
Published: April 2003

AbstractThe variations of photoelastic behavior for styrenedivinylbenzene copolymers and a diallyl phthalate polymer were studied between 20 and about 190°C. The birefringences for constant stresses were measured. With suitably crosslinked polymers the transition from the glassy state to the rubber‐like state was observed distincitly. In the higher temperature region the photoelastic behavior was in agreement with the statistical theory for ideal rubbers. The photoelastic coefficient in the entropy elasticity range varied linearly with increasing degree of crosslinkage. The extrapolated value of Δn/σ for styrene copolymers to zero content of the crosslinking agent coincides with the value for polystyrene itself. With the very highly crosslinked polymer the transition was observed not to be distinct.
The dipole moments and the structure of polyoxymethylene dimethyl ethers
Authors: Uchida Tadashi , Kurita Yukio , Kubo Masaji 
Published: April 2003

AbstractThe dipole moments of monoxymethylene dimethyl ether and dioxymethylene dimethyl ether were measured in hexane solution. From the dependence of the moments of these compounds on the number of oxygen atoms as well as from the temperature dependence of the moments of monoxymethylene dimethyl ether, it was concluded that these compounds are mixtures of rotational isomers, the predominant ones of which assume helical or almost helical structures arising from the gauche minima in the internal rotation about single bonds. The trans minimum, which is 1.74 kcal./mole higher than the gauche minima, is also significant and gives rise to rotational isomers having configurations deviating from the simple helical structure.
Über naturliche und synthetische amylose. V. Über oxyäthylamylosen1
Authors: Husemann E. , Resz R. 
Published: April 2003

AbstractDa die Untersuchung von Amylosen durch einige Faktoren wie z.B. variable Molekülgestalt und schwierige Löslichkeitsverhältnisse erschwert ist, wurden wasserlösliche Oxyäthylamylosen verschiedenen Substitutionsgrades hergestellt und auf ihre Eignung geprüft, als Modellsubstanzen für Amylose zu dienen, insbesondere bei fermentativem Abbau und zur Feststellung etwaigen Abbaues bei verschiedenen Reaktionen.
Crystallinity studies of polyamides by infrared, specific volume and X‐ray methods
Authors: Sandeman I. , Keller A. 
Published: April 2003

AbstractExamination of the infrared absorption of three nylons, polyhexamethylene sebacamide, polyhexamethylene adipamide, and polycaproamide (nylon 6,10, 6,6, and 6, respectively) revealed the existence of bands associated with crystalline order. These discoveries were utilized in the study of crystallinity of nylon 6,10 and nylon 6 in conjunction with x‐ray and specific volume methods. The work falls into three parts. Part I deals with elementary consideration of dichroism and deduces a method of comparing the intensity of an infrared band in a drawn sample of polymer with that of a disoriented sample. A theory of dichroism in materials that have rotational symmetry about one direction is formulated. The question of measuring the absolute intensity of an infrared band is briefly considered. In Part II the crystallinity content of nylon 6,10 (a polymer chosen for its suitability for testing the method) is determined by using the 940 cm.−1 band and specific volume measurements. The effects of annealing and drawing are studied. Proportionality between change in specific volume and change in infrared absorption is confirmed by experiment up to an annealing temperature of 180°C. Above this temperature specific volume measurements give too high a crystallinity figure. Cold‐drawing is found to be connected with a reduction of crystallinity, and can produce voids. The crystallinity of our samples varied between 20 and 55%. The significance of these figures—absolute and relative—is discussed. An absolute figure of 1.052 for the amorphous density of nylon 6,10 is deduced. Part III deals with nylon 6. The infrared spectrum in the 7.5–12.5 μ region is examined and several of the bands are classified as crystalline or noncrystalline. Variation of these bands is studied when the polymer is annealed, drawn, and melted. Both annealing and cold‐drawing increase crystallinity content. In the drawn samples the crystallites are found to be better oriented than the noncrystalline parts. The direction of the transition moment of the 935 cm.−1 band is determined. X‐ray results reveal a new type of ordering corresponding to a state of packing intermediate between randomness and full crystalline order. Infrared bands at 990 and 720 cm.−1 are found to be connected with this state of order. Direct evidence is obtained that the molecules possess an order in the quenched amorphous state. The density of amorphous nylon 6,10 calculated from this ordering is in complete agreement with the figure deduced in Part II.
Neue ergebnisse über das grenzflächenverhalten von carboxymethylcellulose
Authors: Stüpel H. 
Published: April 2003

AbstractCarboxymethylcellulose ist ein wichtiger Aufbaustoff für Waschmittel, der von allem die Resorptionstendenz des Schmutzes hemmt. Der Wirkungsmechanismus von CMC als Schmutzträger beim Waschvorgang wurde bisher auf die Absorption durch das Textil zurückgeführt. In der Fluoreszenzmikroskopie wurde eine einfache und elegante Methode gefunden, den Adsorptionsort von CMC zu bestimmen. Es wurde gefunden, dass CMC im Waschvorgang nicht an der Faser adsorbiert wird, sondern am Schmutz haftend sichtbar gemacht werden kann. Bei hoher Konzentration im neutralen Bereich, abver vor allem im sauren Millieu gelangt CMC an die Fasern.
Molecular weight distribution of a low conversion polystyrene sample
Authors: Guzmán G. M. 
Published: April 2003

AbstractThe fractionation of a low conversion polystyrene sample has been carried out using the precipitation technique in the system methyl ethyl ketone–methanol. Six fractions were isolated and the cumulative and differential curves plotted according to the customary assumptions. Statistical analysis has also been applied on the basis of a Bernouillian distribution for the fractions. The parameters of the binomial have been calculated by means of Beall's method. The results show a considerable divergence with regard to the usual ones. The accumulation of the MW by the classicial procedure is too rapid from a DP of 5600, and is slightly lower than the binomial from zero to 5600. In addition, the classical procedure does not supply any information with regard to the high MW range of the distribution (DP up to 34,000), which amounts to nearly 18% of the whole sample. The distribution has been reproduced, using Bruns' series, from the successive MW averages, and the result agrees with that of the binomial distribution. On the other hand, the distribution has been worked out kinetically, assuming that combination and disproportionation are both the main mechanisms of termination. The results show that disproportionation occurred about twice as frequently as combination.
On the viscosity of polymer solutions in fine capillaries
Authors: Lifson Shneior 
Published: April 2003

AbstractWhen a polymer solution flows through fine capillaries there should be an increase of the apparent viscosity as a result of the inhomogeneity of the flow. This increase is dependent on the ratio between the dimensions of the macromolecules and the capillary. It is independent of the rate of flow as long as the assumed spherical symmetry of the macromolecule is not disturbed by the hydrodynamic forces. The change in the apparent specific and intrinsic viscosities of such solutions is calculated for two forms of capillaries, i.e., parallel planes and cylinders.
A statistical model for amylopectin and glycogen. The condensation of A‐R‐Bf−1 units
Authors: Erlander Stig , French Dexter 
Published: April 2003

AbstractThe authors have developed a statistical model for a branched polymer built from a monomeric unit (such as glucose) which has two types of reactive groups (aldehydic and alcoholic). The treatment differs from that of Flory's in that the different B groups in the A‐R‐Bf‐1 monomer have differing reactivities instead of equal reactivities. The mole fraction of a particular x‐mer having b1, b2,…bf‐1 linkages at their respective B1, B2,…Bf−1 functional groups is:

where \documentclass{article}\pagestyle{empty}\begin{document}$ x = 1 + \sum\limits_{i = 1}^{f - 1} {b_i}$\end{document} is the total number of monomer units per molecule and p1,p2,…pf‐1 are the probabilities that any monomer unit is linked at the B1, B2,…Bf‐1 functional group. From the above, x̄n, the number‐average DP, x̄w, the weight‐average DP, x̄z, the Z‐average DP, and wx, the weight fraction of an x‐mer, have been obtained. It is shown that the limit of x̄z/x̄w is 3 and the limit of x̄w/x̄n is infinity as the degree of polymerization increases for all cases where “f” is greater than two. These results were used for the randomly branched polymers, amylopectin and glycogen, where the functionality of the monomer in both cases is three. p4 and p6 were used to represent the probabilities that any glucose unit is linked at the 4 or 6 position. Using values of p6 = 0.05 and p4 = 0.94933, x̄n = 1500, M̄n = 243,000, M̄w=35,100,000, and M̄z = 104,500,000, giving M̄w/M̄n = 140 and M̄z/M̄w = 2.99. Literature values for molecular weights of amylopectin and glycogen are compared with the above statistical model and with less random statistical models.
Specific heat of synthetic high polymers. VII. Polyethylene terephthalate
Authors: Smith Carl W. , Dole Malcolm 
Published: April 2003

AbstractFrom specific heat measurements on drawn, undrawn, and annealed polyethylene terephthalate over the temperature range – 10 to 280° it has been possible to observe the magnitude of: (a) the glass transition, (b) recrystallization effects, and (c) the change of crystallinity with temperature. The change in the function cp/T at Tg is shown to be roughly proportional to the fraction of amorphous polymer present. Drawing the fiber reduces Δcp/T, but increases the rate of recrystallization so that, on the unannealed drawn samples, recrystallization occurs over a range of temperatures such that the glass transition cannot be observed. Good agreement is obtained between the crystallinity estimated from enthalpies and that calculated from density data except in the case of the samples that recrystallized during the calorimetric measurements. The estimated heat of fusion is in agreement with that calculated from the statistical thermodynamic theory of the effect of copolymers on the melting point. The influence of the surface free energy of the crystallites on their melting point. The influence of the surface free energy of the crystallites on their melting range is discussed.
Flow birefringence behavior of some amylopectins and limit dextrins
Authors: Stacy Carl J. , Foster Joseph F. 
Published: April 2003

AbstractThe flow birefringence behavior of some amylopectins and their limit dextrins are reported. Though no quantitative interpretation is possible due to the great heterogeneity and their probable deformation in the flow gradient, several characteristics seem quite general. The extinction angle is relatively independent of the flow gradient. The gradient range over which observations could be made was limited at the lower end by lack of precision and at the higher end by precipitation which invariably occured. The birefringence curves characteristically showed a saturation behavior. Possible qualitative explanations for the observed behavior are discussed.
Ladder structures for representation of viscoelastic systems. II
Authors: Gross Bernhard 
Published: April 2003

AbstractThis paper presents the theory of a model that consists of identical springs and dashpots arranged in the form of a ladder network. The expressions for complex compliance and complex modulus function are given in closed form; creep and relaxation function are given by series expressions. Comparison of the relaxation spectrum derived from this model with that of Rouse's theory shows both expressions to be identical. Therefore all other expressions obtained with the aid of the model apply equally to Rouse's theory and the model represents a convenient working scheme for the completion of the latter. A discussion of the temperature effect is given.
Light scattering by solutions of polyethylene in 1‐chloronaphthalene
Authors: Moore Louis D. 
Published: April 2003

AbstractA Brice‐Phoenix light‐scattering photometer was modified for use at elevated temperatures by enclosing the cylindrical cell filled with solvent in a tightly fitting copper block wrapped with heating wire. Heat input was controlled by a regulated Powerstat. Temperature was measured by a copper‐Constantan thermocouple and maintained at 125 ± 2°C. This regulation was considered adequate for use with solutions of polyethykene in 1‐chloronaphthalene. Solutions were placed in scattering cells which were shaped like Erlenmeyer flasks and could be easily removed and replaced in the bath of 1‐chloronaphthalene. Commercial polyethylenes from four sources were studied with this instrument and surprisingly large dissymmetries in scattering were encountered in these samples. These dissymmetries sometimes led to correction factors greater than 6 on molecular weights measured at 90° [P−1 (90°) > 6]. Another surprising and significant finding was that polyethylenes from different sources has strikingly different light‐scattering properties. In general, the results obtained lend support to the recent theories of Roedel and Beasley on the mechanism of “long‐chain” branching and its influence on molecular‐weight distribution. Samples were found to vary in their distribution ratio (weight‐average molecular weight/apparent number‐average molecular weight) from 2.5 to 70. According to the Beasley theory this last figure would indicate as many as 140 “long‐chain” branches per weight‐average molecule.
Preparation and properties of fibers containing mixed polymers. II. Polyacrylonitrile‐cellulose fibers
Authors: Cates David M. , White Howard J. 
Published: April 2003

AbstractIn the previous paper the preparation and properties of fibers containing both polyacrylonitrile and cellulose acetate were discussed. It has proved possible to hydrolyze the cellulose acetate without extensive side reactions to produce fibers containing both cellulose and polyacrylonitrile. The properties of such fibers are discussed in this paper. The fibers have been examined optically and using x‐ray diffraction techniques. The absorptive capacity for water and direct dyes, the density, the electrical resistivity, and the mechanical properties of the fibers have been measured. The results are compatible with a structure consisting of submicroscopic regions of each polymer throughout the fiber interspersed with void spaces that are probably produced during drawing.
The structure of crystalline 1,2‐polybutadiene and of other “syndyotactic polymers”
Authors: Natta G. , Corradini P. 
Published: April 2003

AbstractWith the aid of anionic polymerization catalysts, 1,2‐polybutadiene of high molecular weight has been synthesized. It is a crystalline material with a melting point above 150°C. Electron and x‐ray diffraction studies with oriented films permitted determination of the elementary cell, the space group, and the coordinates of the individual carbon atoms in the cell. The chains deviate slightly from the conventional planar zig‐zag structure, the vinyl group substituents are arranged in the 1–3 sequence with alternating D and L configurations. It is proposed to call this type of spatial arrangement in head‐to‐tail vinyl polymers a syndyotactic arrangement. Also polyvinyl chloride, obtained with free radical catalysts, contains small ordered regions, with a structure similar to syndyotactic 1,2‐polybutadiene.