bluuebunny/crossref_metadata_2025 huggingface dataset:
Monolayer studies of some ethoxylin resin adhesives and related compounds
Authors: Glazer J.
Published: April 2003

Compression isotherms of monolayers of ethoxylin resins and related compounds have been studied at the air–water interface, and the orientation of such monolayers at the interface has been described. The monolayer thickness has been measured by the multilayer technique. It has been shown that resin‐substrate adhesion is strongly dependent on the hydroxy group content of the resin, and is independent of the epoxy group content, the molecular weight, and the hydrocarbon group content of the resin. Furthermore, it has been shown that the presence of epoxy groups results in high intermolecular cohesion of the prehardened resin; this, in turn, will tend to minimize resin shrinkage during the hardening process and thus improve the joint strength.
Theory of mechanochemical systems
Authors: Asakura Shô , Imai Nobuhisa , Oosawa Fumio
Published: April 2003

An electrolytic theory is developed for the swelling and deswelling mechanism of mechanochemical systems by methods established by the authors, who are concerned with the problem of polyelectrolyte solutions. The model employed in the theory is a macroscopic cylindrical fiber of rubberlike material with many dissociative radicals. It is assumed, for the sake of simplicity, that the average charge density of the ionized radicals is spread uniformly inside the fiber. The result of the theory shows that almost all the gegenions are bound by the fiber, and that the contributions of the electrostatic energy and entropy to the electrostatic free energy are two‐ and three‐dimensional, respectively, when the density of the ionized radicals remains constant. In combination with theoretical results of rubberlike elasticity and of nonelectrolytic swelling, it is concluded that the osmotic pressure of the gegenions bound by the system makes the system swell against the restoring force due to the rubberlike elasticity of the system. The free swelling of systems is, for instance, expressed by the following relation:

where α is the relative elongation, N the number of the dissociative radicals per chain ξ the degree of neutralization, and B the factor due to the full stretching effect of each chain. This relation is in good agreement with experimental results.
Application of rhodamine‐B to interaction studies in proteins and simple model systems
Authors: Lundgren Harold P. , Binkley Charles H.
Published: April 2003

With rhodamine‐B used as an indicator, the relative acidities of selected phenols and alcohols as model hydrogen donors have been determined in toluene solution. The method involves measurement of the change from colorless rhodamine to the colored zwitterionic form produced by the hydrogen donor compound. The method has been applied to the determination of equilibrium constants for the interaction of phenol with dimethyl formamide, benzyl acetate and dioxane; the measured constants are in accord with those obtained for the same pairs by Flett (J. Soc. Dyers Colourists, 68, 59–64 (1952)), who employed infrared analysis. Consideration is given to partition of the dye between toluene and water, as influenced by hydrogen bonding and by nonelectrostatic interactions. Forces of interaction which tend to bind the dye in one phase decrease its activity in that phase and consequently reduce its tendency to move from this phase to the other. With incorporation of propiolactone polymer into the wool fiber, the activity of the dye in the fiber is reduced in relation to nonpolar as well as to aqueous solutions, and the modified wool exhibits greatly improved dyeing properties. The dye is useful also for the determination of critical micellar concentration of fatty acid soaps in aqueous solution. It also shows markedly increased binding by heat‐denatured as compared with native egg albumin, and by acetylated, as compared with normal, wool.
Vulcanization of crepe rubber by sulfur monochloride. Part I. The gelation method
Authors: Glazer J. , Schulman J. H.
Published: April 2003

When a solution of natural rubber hydrocarbon is cold vulcanized with sulfur monochloride, a gel is formed. The rate of gel formation is used to characterize the rate of reaction between rubber and sulfur monochloride and a preliminary kinetic investigation is described. It is shown that the reaction is accelerated by compounds normally used for speeding up sulfur (hot) vulcanization, and it is suggested that these function by virtue of their possessing an active hydrogen atom. Several series of simple compounds, containing the groups SH, OH, and NH2, are shown to function as effective accelerators and their activity is attributed to the presence of a labile hydrogen atom in the molecule RXH, where R = organic radical and X = S, O, or N. The absence of a direct relationship between accelerating power and basic or acidic strength suggests a free radical mechanism of accelerator action, based upon the process
${\rm R} - {\rm X} - {\rm H } \to {\rm R} - \mathop {{\rm X }}\limits^ * {\rm + }\mathop {{\rm H }}\limits^ * $.
Thermodynamics of the mechanical properties of cellulose fibers
Authors: Roseveare W. E. , Poore L.
Published: April 2003

Measurements are reported for the reversible changes in force with temperature at constant length of wet and dry viscose rayon and wet ramie. It was found that the force was a reversible function of the temperature although the components of its thermodynamic equivalent, the product of modulus and coefficient, are very time dependent. The entropies of stretching obtained as the negative slopes of the force‐temperature curves are interpreted in terms of the mechanisms of reversible stretching. Completely dry rayon is glasslike and shows no slippage of chains but only deformation of valence bonds and angles on reversible stretching. Wet rayons exhibit a rubberlike slippage of chains above 50°C. but below this temperature chain movement is restricted. This inhibition of the chains produces at low temperatures a yield point in the wet stress‐strain curves and poor work recovery. Sodium hydroxide, although speeding up stress relaxation, has no effect on the reversible stretching of the amorphous wet cellulose. In room air, the entropy of stretching is opposite to that of completly dry rayon even up to 92°C. Wet ramie appears to be in the glassy state like the completely dry rayon.
Breakage of rubber‐filler linkages and energy dissipation in stressed rubber
Authors: Blanchard A. F.
Published: April 2003

The stress–strain behavior of reinforced rubber is discussed in respect of the softening with applied stress and accompanying dissipation of energy. The concept of linkage strength factors X for attachments between rubber molecules and filler particles is shown to have wide application and usefulness, and to be related to the energy dissipated in breaking the linkages. The strength factors are a function of the prestress when the linkages break, and also the corresponding extension ratio and residual stiffness; and for a variety of fillers and considerable range of values they can be roughly converted to energies of breakage in calories per unit change in modulus by multiplying by η = 0.013. The range of strengths of these secondary linkages due to fillers may be expressed in terms of X by one distribution parameter K common to widely different rubber compounds. Energy data suggest that they are formed by physical attachments involving a number of chemical groups in the long chain polymer molecules. Presumably the strength distribution is mainly due to differences in the number of groups involved. The particle diameter of the filler has little or no importance in determining the energy dissipated in breaking secondary linkages, or their number as judged by stiffening action; yet it is a major factor in reinforcement as judged by tensile strength, tearing, and abrasion. Considerations of secondary linkages in conjunction with particle diameter show no prospect of explaining the differences in reinforcing action between types and grades of filler. An appreciation of the presence of some of strong‐type (primary) linkages due to carbon black is apparently necessary to understand the wide differences between fillers in the energy dissipated on breaking secondary linkages by a fixed prestress.
Solvent independent parameters in the viscometry of polymer solutions
Authors: Cleverdon D. , Smith P. G.
Published: April 2003

Evidence is discussed for and against the existence of a common meeting point when linear plots of ηsp/C against C for polystyrene in a number of solvents are extrapolated to negative concentrations. There is rather more evidence in favor than against, and most of the contrary evidence falls into a category for which exceptional behavior might be anticipated. The ordinate of the common meeting point, unlike the limiting viscosity number, is independent of solvent and is conveniently called the true limiting viscosity number [η]T. [η]T has been identified with the intrinsic configurational character of a polymer chain. The common point of intersection has the coordinates [η]T and C2, where Cx is a negative concentration. The product of [η]T and Cx has been found to be constant over a considerable molecular weight range. This leads to an expression for [η]/[η]T in terms of Huggins' k′. [η]/[η]T represents the ratio of the hydrodynamically equivalent volume of a polymer in an actual solvent to the equivalent volume of the chain in its natural state of extension. [η]T is considered in relation to [η]θ (Flory‐Fox) and [η]P (Bawan). The effect of polymer heterogeneity is discussed.
A thermostat for light scattering measurements
Authors: Casassa Edward F. , Katz Sidney
Published: April 2003

A thermostat for light scattering studies is described in which the glass cell containing the solution under investigation is immersed in water maintained at constant temperature. The construction is such that the phototube used for detection of scattered light is at room temperature whatever the temperature of the sample. The liquid bath about the sample cell minimizes both troublesome reflections of the incident light and errors arising from refraction effects.
Small angle x‐ray scattering of rayons swollen in lithium hydroxide solutions
Authors: Hermans P. H. , Weidinger A.
Published: April 2003

In continuation of a previous investigation on the small‐angle scattering of rayons in the dry and water‐swollen condition, a number of samples are investigated in lithium hydroxide solutions of increasing concentration up to 5 N, in which considerably higher degrees of swelling can be reached. In samples showing an intensity maximum in the water‐swollen condition, the locus of this maximum shifts to smaller angles upon further swelling in LiOH solutions, to disappear in 5 N solutions. Samples exhibiting neither a maximum nor an inflection point in no case yield straight Guinier plots even at the highest degree of swelling attained.
Hydrodynamic properties of urea‐denatured fibrinogen
Authors: Scheraga H. A. , Carroll W. R. , Nims L. F. , Sutton E. , Backus J. K. , Saunders J. M.
Published: April 2003

The hydrodynamic properties of native and urea‐denatured fibrinogen have been investigated, primarily to examine further the suggestion, based on a consideration of data for horse serum albumin, that urea denaturation may involve swelling instead of increased asymmetry. A sedimentation‐diffusion and also a light scattering molecular weight determination at the isoelectric point indicate that 6 M urea causes neither splitting nor aggregation of the native protein in the denaturation process. The observed increase in the intrinsic viscosity and frictional coefficient upon denaturation can be interpreted in terms of an equivalent hydrodynamic ellipsoid of approximately the same shape but of a volume which is approximately 1.7 times that for the native protein. The effective volume appears to be slightly dependent on pH with a minimum at the isoelectric point. It thus appears that the urea denaturation of bovine fibrinogen, like that of horse serum albumin, may involve swelling. There is no indication in the case of either protein that increased asymmetry is involved in accounting for the frictional behavior of the denatured substances.
Molecular dimensions in relation to intrinsic viscosities
Authors: Newman Seymour , Krigbaum William R. , Laugier Claude , Flory Paul J.
Published: April 2003

Root‐mean‐square end‐to‐end dimensions (r2)1/2 and molecular weights M have been determined from light scattering studies carried out on a series of fractions of poly‐(acrylic acid) in dioxane (θ point, 30°C.), on two polyisobutylene fractions in cyclohexane and in ethyl n‐caprylate (θ point, 22°C.), and on a single poly‐(methyl methacrylate) fraction in acetone. Intrinsic viscosities of the various polymers measured in these same solvents at the same temperature (30°C.) support the relationship [η] = Φ(r2)3/2/M, where Φ is a constant independent of molecular weight and solvent type and (according to the data herein reported) has the approximate value 2.2 × 1021. The θ points, representing the temperatures at which ideal behavior prevails, were determined for the two poor solvent–polymer systems by extrapolation of critical consolute temperatures to M = ∞. The intrinsic viscosity of poly‐(acrylic acid) in dioxane at 30°C. (the θ point) is given by [η] = 0.85 × 10−3M1/2; the value of the constant approximates those for nonpolar polymers.

The influence of molecular weight heterogeneity on the fundamental relationship of the intrinsic viscosity to (r23/2/M) is analyzed, and it is shown that the true value of the universal parameter Φ will be greater than the apparent value deduced in the foregoing manner without correction for the heterogeneity of the polymer fraction. For a fraction possessing a relatively sharp distribution as denoted by 〈M〉w/〈M〉n = 1.15. the magnitude of this correction may be as high as 20%.
Use of deuterium to investigate extent of branching in polystyrene
Authors: Wall Leo A. , Brown D. W.
Published: April 2003

The extent of branching in polystyrene is attributed to a polymer transfer step occurring during polymerization. In this process a radical abstracts a hydrogen atom from along a chain which then adds monomer at the site of the abstraction. The rate of this process should be decreased if the hydrogen is replaced by deuterium, and consequently deuterated monomers should polymerize to form polymers less branched than those from the nondeuterated monomer. Polymers of α‐ and β‐deuterostyrene were synthesized and thier intrinsic viscosity and molecular weight by light scattering determined. In the case of the α‐deuterostyrene, the polymer was also fractionated and measurements were made on the fractions. The data for the deuterated styrenes fit quite closely the same relationships as a normal styrene sample prepared simultaneously and under the same conditions, i.e., 70°C. and without catalyst. The results indicate, therefore, that branching is quite small in polystyrene prepared under such typical conditions. A check of the isotope effect on the transfer process was made utilizing S‐deuterobutyl mercaptan. A value of 4.0 was obtained at 60°C. for the relative rate of transfer with butyl mercaptan to that for the deuterated mercaptan.
Multiple dispersion regions in rigid polymeric systems
Authors: Buchdahl Rolf , Nielsen Lawrence E.
Published: April 2003

It is shown how chemical and colloidal heterogeneity can result in multiple dispersion regions of the mechanical or electrical loss factor as a function of temperature. Heterogeneity can be produced in several ways: (a) mechanical blending (mixing) of certain polymers, (b) non‐uniform copolymerization, (c) block or graft polymerization, (d) external plasticization, and (e) certain types of molecular weight distribution. Specific examples are given to demonstrate the effect.
Unusual orientation phenomena in polyethylene interpreted in terms of the morphology
Authors: Keller A.
Published: April 2003

In the first part of the paper various orientation phenomena of the drawing‐relaxation behavior are interpreted in terms of the changes occurring within the submicroscopic helices which form the spherulites. Not only drawing and relaxation but also the redrawing of the relaxed samples were followed, and it was shown that the observed anomalous orientation effects cannot be described in terms of tilts of planes with simple indices. However, by considering also the possible shapes of the submicroscopic units these orientation effects can be visualized. In the second part a new general type of orientation, the “row orientation” is introduced. This arises when crystallization takes place while the melt is flowing. Flow produces lines of high nucleus density, leading to growth of the crystallites in all directions perpendicular to the direction of drawing. This results in elongated aggregates of helices, and the alignment of these complex units produces a unique type of orientation which has been established from various angles.
Infrared study of oxidation of elastomers
Authors: Field J. E. , Woodford D. E. , Gehman S. D.
Published: April 2003

Infrared absorption spectra were used to study the structural changes resulting from oxidation in a number of unvulcanized, purified polymers under a variety of experimental conditions. The results showed that as oxidation progressed, the structural changes which were detected were qualitatively the same for all of the polymers under all of these experimental conditions. Correlation of volumetric measurements with spectral data indicated that considerably more oxygen was absorbed by the polymer samples before structural changes could be detected than the minimum amount required for the initial detection of the hydroxyl and carbonyl structures. From the interpretation of information from the absorption spectrum, it is believed that the structural evidence is in substantial agreement with current theories on autoxidation. Although the initial hydroperoxide formation is not observed in the spectrum, it is quite probable that this reaction takes place with almost immediate decomposition which results in a net hydroperoxide concentration so low as to make infrared methods insensitive for its detection. Correlation of physical properties with structural studies indicate that little change in these properties take place until the hydroxyl and carbonyl structures become evident in the infrared spectrum.
Interaction of polydimethylsiloxanes with swelling agents
Authors: Bueche A. M.
Published: April 2003

The swelling of a crosslinked polydimethylsiloxane in a number of swelling agents has been measured. Values of the solvent‐polymer interaction parameter, χ1, have been computed and have been compared with the solubility parameters of the swelling agents and with other data from the literature. The magnitude of the solubility parameter of the polymer depends markedly on the swelling agents and method used for its estimation. The values reported here range from 7.7 to 5.03.
Investigation of unusual orientation in polyethylene by infrared spectroscopy
Authors: Keller A. , Sandeman I.
Published: April 2003

A quantitative analysis of the 725 cm.−1 doublet in the infrared spectrum of polyethylene is given and used to check the “row” model of polyethylene, as it naturally crystallizes from drawn melt. This analysis depends on a new interpretation of the 725 cm.−1 doublet, according to which the 730 cm.−1 component has its transition moment along the a crystallographic axis, and the 720 cm.−1 component along the b axis. The amorphous polymer gives only a band at 720 cm.−1. The analysis in certain cases enables the amount and orientation of the amorphous component of the polymer to be determined. From similar considerations, variations in the relative intensity of the two peaks in the course of drawing unoriented polyethylene are explained.
Phase separation in solutions of vinyl polymers
Authors: Kern R. J. , Slocombe R. J.
Published: April 2003

When polymers of two different chemical species are dissolved in a common solvent the resulting solution usually separates into two phases. No obvious relation between phase separation and chemical nature of the monomeric units was observed. Solute molecular weight, temperature, and nature of the solvent were shown to be factors in determining the course of phase separation. A concept of phase separation is suggested which involves low entropy of mixing, greater attraction between like than unlike species of solute, and density differences between solvated polymer molecules.
A kinetic interpretation of the rheological behavior of high polymers
Authors: Furukawa Junji
Published: April 2003

A chemical kinetic interpretation of the rheological behavior of high polymers has been proposed, in which the polar force of segments locks the adjacent segments in neighboring molecules in a similar way to crosslinking in vulcanized rubber. The change of such a crosslink caused by the thermal motion of segments and by external stress on the sample gives rise to rheological phenomena, such as the relaxation of stress or strain. The elasticity or viscosity of high polymers is related to the equilibrium crosslinkage which is affected not only by the temperature change but also by external stress. The structural viscosity, the yield point, or the effect of solvent on elasticity or on viscosity can also be understood according to this interpretation. The theoretical treatment gives many equations previously found in experiments: the equation for relaxation of deformation or stress, i.e., the four‐element‐model equation, the Dienes' equation with respect to the temperature dependence of elasticity of polyvinyl chloride, or Rabinovitch's equation for structural viscosity.
The pyrolysis of p‐xylene
Authors: Schaefgen John R.
Published: April 2003

A quantitative study of the pyrolysis of p‐xylene at temperatures from 795° to 920° at low pressures has been made using a flow system at low contact times. A mechanism is postulated to account for the principal products. The primary rate controlling reactions are the dissociation of either a CH bond in the methyl side chain or a CC bond from the ring to the methyl group, the activation energies of which are 79 and 82 kcal., respectively. Evidence is presented for the existence of the intermediate p‐xylylene molecule, and for its formation by disproportionation from the initially formed p‐methylbenzyl radicals. The copolymerization of p‐xylylene with maleic anhydride or chloroprene is described.
Polymer chain dimensions in mixed‐solvent media
Authors: Shultz A. R. , Flory P. J.
Published: April 2003

The equilibrium between a linear polymer molecule and a binary solvent mixture in which it is immersed has been treated. An equation has been derived relating the resulting molecular expansion to the thermodynamic parameters for the ternary system and to the solvent composition. Intrinsic viscosity measurements are reported for polystyrene fractions in three mixed‐solvent systems: methyl ethyl ketone‐methanol, carbon tetrachloride‐cyclohexane, and benzene‐cyclohexane. Intrinsic viscosities measured for polystyrene fractions in critical consolute mixtures agree with those found in single poor solvents at the analogous Theta points. Intrinsic viscosities have been measured over ranges of mixed‐solvent composition for the second and third solvent mixtures mentioned. Poor agreement with theory is observed for the former, but the more extensive measurements in benzene‐cyclohexane mixtures agree very well with theoretically calculated intrinsic viscosities.
Sorption of nitrogen dioxide by cellulose acetate
Authors: Myles William J. , Reiss Howard
Published: April 2003

Sorption of NO2 by cellulose acetate proceeds by a process of solution, diffusion, and reaction governed by Henry's law, Fick's law, and first order kinetics with respect to the consumption of NO2. It appears as though water is the primary substrate with which NO2 reacts in the acetate film. The pseudo‐unimolecular rate constant for films conditioned at 50% RH seems to be about 10 ± 5 × 10−3 sec.−1. The solubility of NO2 in dry film increases with increasing degree of acetylation. With the present data the diffusion coefficient and solubility in moist films cannot be determined separately, but only jointly as a parameter involving the product of one by the square of the other. Improved experiments designed to yield precision during the later stages of the sorption process should yield separate values of the two constants.
The degradation of cellulose by ionizing radiation
Authors: Charlesby A.
Published: April 2003

When subjected to the effect of ionizing radiation, such as atomic pile radiation or gamma radiation, cellulose is rapidly degraded into a powdery material. A theoretical treatment shows that if the effect of radiation is to cause fracture at random in the main chain, the relation between intrinsic viscosity [η] and radiation dose R should be of the form:

where R0 is a “virtual” radiation dose needed to produce the initial number‐average molecular weight from a chain of infinite molecular weight. The published data of Saeman, Millett, and Lawton have been used to verify this formula, which leads to a relationship between [η] in cupriethylenediamine and viscosity‐average molecular weight Mv:

with α = 0.71. The constant K has been evaluated by comparison with data given by Gralen, but is less accurately known. It is deduced that one million roentgen results in fracture of 0.16% of the monomer units in the main chain. The decomposition of carbohydrates under radiation, which occurs at the same time as main chain fracture, can be explained on the assumption that approximately one monomer unit is decomposed per main chain fracture. The study of intrinsic viscosity of irradiated polymers appears to offer an accurate means of evaluating α in the usual formula for intrinsic viscosity [η] = KMα.
Vinyl polymerization. III. Polymerization of acenaphthylene
Authors: Imoto Minoru , Takemoto Kiichi
Published: April 2003

Polymerization of acenaphthylene by boron trifluoride‐ether complex as catalyst was carried out in benzene solution of various concentrations of the catalyst over a range of temperatures from 20 to 50°C. Over‐all rate of the polymerization was found to be of the first order both for the initial concentration of the monomer and for that of the catalyst:

Activation energy required in the reaction was calculated to be 12.5 kcal./mole, and the molecular weight of polymers measured by the Gee osmometer was shown to be of the same order as found by previous workers.
Absorption and swelling by nitrocellulose fibers and films in binary solvent–hexane mixtures
Authors: Moore W. R.
Published: April 2003

Absorption of solvent and swelling by nitrocellulose fibers and films, in binary solventhexane mixtures of varying concentration and involving ketones, acetates, and phthalates, have been compared. Equilibrium is less rapidly attained with films. With solvents of smaller molecular size the equilibrium absorption of fibers and films, at a given concentration, is the same, suggesting that all regions of the nitrocellulose are accessible to such solvents. With solvents of larger molecular size lower equilibrium absorption values are obtained with films, suggesting that only certain regions are accessible to these solvents and such accessibility is less in films. Where absorption values are similar, swelling of films and fibers are comparable and similar modes of solution are observed. The assumption that no hexane is absorbed appears to be justified at lower solvent concentrations, but at higher concentrations the mixture in equilibrium with the nitrocellulose may be imbibed. Assuming such imbibition, the relationship between swelling or solvent power and cohesive energy density of solvent is interpreted in terms of interaction between solvated polymer and mixture.
Studies of the ethylenediamine‐cellulose complex. I. Decomposition of the complex by solvents
Authors: Loeb Leopold , Segal Leon
Published: April 2003

The ethylenediamine‐cellulose complex, previously described by Trogus and Hess, has been reinvestigated with regard to its stability toward a series of solvents and to the differences in the fine structure of the cellulose remaining after its decomposition. It is shown that nonpolar solvents which do not contain oxygen have little effect on the complex; they do not reduce the diamine content or alter its crystal structure. On the other hand, it has been found that polar, oxygen‐containing solvents almost completely remove the diamine and, in general, cause a reconversion of the crystal structure to the cellulose I crystalline modifications. The nature of the fine structure of the cellulose remaining after decomposition of the complex is discussed in relation to the directive or orienting influence of the solvent used for the decomposition. It is shown empirically that the directive influence of a solvent is related to its polarity and to the temperature at which the decomposition is effected.
Structure of polysiloxanes: Influence of solvent on size and polymer‐solvent interaction of linear polydimethylsiloxanes
Authors: Price Fraser P. , Bianchi Joseph P.
Published: April 2003

Molecular weight, sizes, and second virial corfficients of a linear polydimethylsiloxane polymer (MW = 4.57 × 105) in mixtures of toluene‐diethylphthalate have been determined by light scattering. Intrinsic viscosities have also been measured in the same mixed solvents. As expected, as the diethylphthalate concentration was increased the molecules contracted and the second virial coefficients became more negative. The data were used to attempt to decide between two current theories relating these quantities. No choice could be made. It was found that the calculated values of Flory's universal constant, φ, were much smaller than those usually obtained. It is proposed that this is due to an abnormally broad molecular weight distribution in the polysiloxane.
Ultrasonic degradation of cellulose nitrate: Relation between initial and final average and distribution of DP
Authors: Thomas Berwyn B. , Alexander W. J.
Published: April 2003

Cellulose nitrates of average DP 130 to 2400 and of various DP distributions were degraded in ethyl acetate solutions by ultrasonic energy at 400 kilocycles. A method of comparing degradation rates of samples degraded at different concentrations is described. The degrees of degradation found were in accord with the theory of Schmid and co‐workers, and the minimum degradable chain length was calculated to be 980 DP in this system. Where compared with degradation by alkaline aging, ultrasonic degradation gave a much more uniform chain length distribution. After ultrasonic treatment, 60% of the sample was of DP 700 to 1200, while the alkaline aged sample had less than 40% in this same range and a much larger amount of short chain length material. The results do not give any indication of the presence of any physically or mechanically weak chain links at any interval near 500 DP.
Influence of molecular weight and degree of crosslinking on the specific volume and glass temperature of polymers
Authors: Fox T. G. , Loshaek S.
Published: April 2003

On the basis of simple assumptions, equations are derived for predicting the specific volume‐temperature‐molecular weight (v‐T‐M) relationships for a homologous series of polymers from the v‐T curves for the monomer and the polymer of infinite molecular weight. Analogous v‐T‐ρ relationships (where ρ is the degree of crosslinking) are similarly obtained. The result, that v decreases linearly with decreasing 1/M and with increasing ρ, conforms with the picture that either the removal of two chain ends (as M increases) or the introduction of a crosslinkage involves, between two polymer segments, the exchange of a van der Waals bond for a shorter covalent bond. The validity of these equations is illustrated by comparison with the observed data for polymers covering a wide range in M, T, and chemical type. For several polymer series the extrapolated value of v at 0°K (v0) is the same for all members of the series, indicating that at this temperature the average length of the van der Waals and covalent bonds between polymer segments are the same. Assuming that the form of the linear relationship observed for polystyrene between the specific volume (vg) at the glass temperature and the value (Tg) of the latter is valid for other polymer series, equations are derived which predict Tg as a function of M from the limiting value of the glass temperature for a chain of infinite length, and from the v‐T curves in the liquid state for the monomer and for the polymer of M = ∞. Analogous Tg‐ρ relationships are similarly obtained. According to these equations, a linear relationship between 1/Tg and 1/M should be obtained, which reduces at high M to a linear dependence of Tg on 1/M. Similarly, a linear dependence of Tg on ρ is predicted at low ρ. These predictions are in satisfactory agreement with data on polystyrene fractions and on crosslinked copolymers of styrene with divinylbenzene.

The conclusion that Tg for polystyrenes represent a state of iso‐free volume irrespective of M is shown to be an approximation that is valid, within experimental error, only for large values of M.
Crosslinked polymers. II. Glass temperatures of copolymers of methyl methacrylate and glycol dimethacrylates
Authors: Loshaek S.
Published: April 2003

Glass temperatures are given for copolymers containing methyl methacrylate and from 0 to 100% of each of the dimethacrylates of ethylene glycol (EGDMA), decamethylene glycol (DGDMA), and 2‐ethyl‐2‐butylpropanediol‐1,3 (2‐E‐2‐B‐PDMA), and for copolymers containing from 0 to 17 mole per cent of the dimethacrylate of 2,2‐dimethylpropanediol (2‐2‐D‐PDMA). The relation between Tg and the mole fraction of dimethacrylate in the copolymers is complex, maxima being observed for the DGDMA and 2‐E‐2‐B‐PDMA copolymers. This unexpected behavior is interpreted on the basis that the introduction of crosslinkages by copolymerization of a vinyl with a divinyl monomer affects Tg by concomitant changes in the average copolymer composition (“copolymer effect”) and the degree of crosslinking (“crosslinking effect”). The copolymer effect is obtained separately for the MMA‐EGDMA copolymers from the observed Tg‐composition relation for copolymers of MMA with ethylene glycol monomethacrylate, monoisobutyrate. The crosslinking effect per se is then calculated on the basis of the assumption that the copolymer and crosslinking effects are independent and additive. For the EGDMA copolymers, it is found that the effect of crosslinking alone causes Tg to increase linearly with an increase in the number (ρ) of crosslinks per gram of polymer, and that the proportionality constant is of the same order of magnitude as that observed in the preceding paper for the styrene‐divinylbenzene copolymers. This observed Tg‐ρ relation is in semiquantitative agreement with the equations of the preceding paper, and lends support to the concept of additivity and independence of the copolymer and crosslinking effects upon which the observations are based. The results on the MMA‐EGDMA copolymers, together with the less extensive data on the other copolymers, indicate that the magnitude of the increase in Tg for each crosslink introduced is essentially independent of the structure of the crosslinker.
Rate of thermal diffusion of polymer molecules in solution
Authors: Hoffman John D. , Zimm Bruno H.
Published: April 2003

Measurements of the thermal diffusion constant of polystyrene in toluene and butyl acetate solutions have been made. Direct observation of a moving boundary was used. There is a small change of thermal diffusion constant with molecular weight, but it is doubtful that it could be used for analytical purposes. The results for polystyrene in toluene have been compared with those obtained by Debye and Bueche with a convection‐type column.
Isopiestic method for determining molecular weights of polymers
Authors: Parrette Richard L.
Published: April 2003

The methods generally used for determination of the molecular weight of polymers usually cannot be used for molecular weights between 1000 and 30,000. This is the range most suitable for determination by the isopiestic method, whereby the molecular weight is measured by comparing the vapor pressure of the polymer solution with that of a solution containing a reference solute. The isopiestic principle can be adapted to polymers if the high degree of dependence of solute and solvent activities upon concentration can be evaluated. This is easily accomplished by plotting the reciprocal of the apparent molecular weight against the concentration and making an extrapolation to infinite dilution. Certain modifications of the conventional isopiestic techniques are necessary in order to accelerate the attainment of isopiestic equilibrium and to eliminate water from the solutions. Isopiestic equilibrium is readily attained if a proper combination of solvent and temperature is chosen, and if the solutions are agitated adequately. Water may be removed by the use of a drying agent in the solutions, although the drying agent causes minor errors which are difficult to correct. Results obtained with the isopiestic method show that it is reliable for molecular weights up to 40,000. The accuracy decreases rapidly with higher molecular weights.
Mechanism of emulsion polymerization of styrene with persulfate as activator in the absence and presence of mercaptan and a retarder
Authors: Kolthoff I. M. , O'Connor P. R. , Hansen J. L.
Published: April 2003

With the use of persulfate containing radioactive sulfur it is shown that the termination reaction of the polymerization of styrene is a coupling of the free radical chains. In the presence of m‐dinitrobenzene as a retarder evidence has been presented that the termination reaction is a disproportionation and not a combination of two free radical chains. Mercaptan in the emulsion polymerization of styrene acts solely as a chain transfer agent. Any chemical reaction between persulfate and mercaptan does not contribute to the initiation. In the presence of detergent the rate of initiation of the polymerization of styrene is equal to the rate of thermal dissociation of persulfate:

Thus, any reaction between persulfate with monomer and detergent does not contribute to the initiation. The much smaller rate of initiation in the absence of detergent is attributed to the slight solubility of styrene, the concentration of the monomer being so small that it cannot capture all the free radicals. The effect of the detergent is a physical one, by its solubilizing action it increases the solubility of the monomer in the water layer to such an extent that the “activator” now becomes 100% efficient.
Vinyl polymerization. IV. Influence of dimethylaniline on solution polymerization of vinyl chloride catalyzed by benzoyl peroxide
Authors: Imoto Minoru , Otsu Takayuki , Kimura Ko
Published: April 2003

In the solution polymerization of vinyl chloride with benzoyl peroxide, it was found that the initial rate of the polymerization was remarkably increased by adding dimethylaniline, but that conversion became constant at lower conversion. It was observed that when the rate became constant the benzoyl peroxide was completely decomposed and the reaction could be reinduced by adding more benzoyl peroxide. On the basis of these results, it seems possible that the polymerization is instituted by the benzoate radical and not by the dimethylaniline radical as suggested by Horner. The benzoate radical is produced through the reaction of dimethylaniline with benzoyl peroxide. In view of such considerations, we postulate a reaction mechanism for the polymerization of vinyl chloride.
Une nouvelle classe de polymeres d'α‐olefines ayant une régularité de structure exceptionnelle
Authors: Natta G.
Published: April 2003

Les propriétés exceptionnelles d'une nouvelle classe d'hydrocarbures macromoléculaires à structure linéaire obtenus par polymérisation d'α‐oléfines sont décrites. La haute température de fusion, la cristallinité élevée, la faible solubilité, les propriétés mécaniques spéciales de ces polymères sont attribuées à une régularité particulière de structure due à l'existence, dans chaque macromolécule, de longues successions ordonnées d'atomes de carbone asymétriques ayant la même configuration stérique. Pour ce type particuler d'ordonnement d'atomes de carbone asymétriques dans des macromolécules linéaires, on propose le terme “isotaxique.”
The Gaussian approximation for a chain with fixed valence angles
Authors: Zimm Bruno H.
Published: April 2003

The Flourier transform method (“Markoff's method”) is used to derive the probability distribution function for the end‐to‐end distance of a chain with fixed bond lengths and fixed valence angles but with free rotation. The usual Gaussian form is found for a large number of bonds.
The melting points of chain polymers
Authors: Bunn C. W.
Published: April 2003

The molecular characteristics which determine the melting points of high polymer crystals are considered, and it is shown that the properties of monomeric crystals often throw light on those of the polymers. The principal factors controlling melting points appear to be molar cohesion energy (of the whole molecule for monomers, or per chain unit for polymers), molecular flexibility (due to rotation round bonds), and molecular shape effects. Figures for the cohesion energy increments of a number of chain units and substituent groups are given, and melting points of polymer series are correlated with cohesion energy per chain unit. The flexibility factor is less easy to assess; barriers to rotation in appropriate monomer molecules are relevant, but available data are very rough. The approach therefore is mainly by empirical and comparative methods. When plotted against cohesion energy per chain unit, the melting points of various series of aromatic polyesters and polyurethans fall within the same band, while those of the polyamides lie on the whole higher and those of the aliphatic polyesters, polyethers, polythioethers and polydisulfides much lower. The differences are attributed to difference of molecular flexibility arising from the presence of easily rotating OC, SC and SS bonds. The low melting points of rubber and other unsaturated polymers are attributed to the fact (which can now be regarded as definitely established by independent evidence) that rotation round single bonds which are adjacent to double CC bonds is easier than in saturated chains. Easily rotating bonds which are inclined to each other, as in cis isomers, confer greater chain flexibility than the parallel bonds in trans isomers, and thus lead to lower melting points. The marked odd‐even effects in saturated molecules which run through the whole of organic chemistry (the even members always melting higher than the odd) are attributed to similar effects arising from the fact that the end bonds of an odd CH2 sequence are inclined to each other while those at the ends of an even sequence are parallel.
Preparation of graft copolymers from autoxidized polystyrene derivatives
Authors: Metz Donald J. , Mesrobian Robert B.
Published: April 2003

Experiments on the low temperature autoxidation of polystyrene and several alkylated derivatives of polystyrene in solution are presented. Whereas the benzoyl peroxide catalyzed oxidation of polystyrene in isopropyl benzene proceeds extremely slowly, the oxidation of a partially isopropylated polystyrene readily yields a stable polymeric hydroperoxide containing up to 3.5 hydroperoxide groups per 100 monomeric units. The repressed oxidizability of polystyrene as contrasted with isopropyl benzene or isopropylated polystyrene is suggested to arise from a steric inhibition of resonance. Experiments on the bulk polymerization of vinyl monomers using polymeric hydroperoxides are described, and the results compared with vinyl polymerization initiated by cumene hydroperoxide. The preparation of a graft copolymer by the redox‐emulsion polymerization of methyl methacrylate using an isopropylated polystyrene hydroperoxide is described.
Surface films of synthetic polypeptides
Authors: Mishuck E. , Eirich F. R.
Published: April 2003

Three synthetic α‐polypeptides were spread on aqueous substrates from suitable molecular solutions, and the surface areas, pressures, compressibilities, etc. measured on a horizontal film balance. On pure water spreading occurred at the best in the form of condensed films, but on aqueous solutions spreading improves with the solute concentration, especially near saturation of lyotropic compounds such as urea or potassium thiocyanate. On such substrates molecular weights (MW) and surface areas (SA) can be calculated by means of a modified van der Waals' equation. The MW and SA obtained as a function of substrate nature are found to be functionally related. The conditions and assumptions under which such a relation may be used to decide on true MW's, and their pertinence for the above polypeptide data, are discussed. Di‐ and trivalent cations in the substrate are found to increase MW's in accordance with their valence.
Apparent transfer constants of mercaptans in emulsion polymerization. I. Role of diffusion and distribution coefficients
Authors: Meehan E. J. , Kolthoff I. M. , Sinha P. R.
Published: April 2003

The chain transfer constants of normal and tertiary mercaptans with polystyrene radicals at 50°C. are, respectively, 19 and 4.5, with polybutadiene radicals, respectively, 19 and 3.7. The values are somewhat larger at 5°C., corresponding to an activation energy for transfer about 1 kcal./mole smaller than for propagation. At equilibrium 0.58 g. of n‐octyl, 0.62g. of tert‐octyl, 0.25 g. of n‐tetradecyl, and 0.26 g. of tert‐hexadecyl mercaptan can be dissolved per gram of polystyrene in emulsion, but the rate of attainment of equilibrium is extremely slow with the higher molecular mercaptans. The small apparent transfer constants of the higher mercaptans in emulsion polymerization are due to the slow rate of transport to the polymer particles. This transport is greatly accelerated by the addition of alcohol, which makes the distribution toward the water layer more favorable. In general the solubility in water of the mercaptan (or modifier in general) is the most important factor, the diffusion coefficient being of only secondary significance in a comparison of compounds of approximately the same molecular weight.
Copolymerization characteristics of ethyl vinyl ether and its beta‐bromo and beta‐carbethoxy derivatives
Authors: Price Charles C. , Schwan Theodore C.
Published: April 2003

The copolymerization of ethyl vinyl ether with acrylonitrile leads to values of the copolymerization parameters of Q = 0.06 and e = −0.8. Calculations from other data in the literature suggested that Q = 0.015 and e = −1.6 are better values. Copolymerization of β‐bromovinyl ethyl ether with styrene and methyl methacrylate indicates Q = 0.014 and e = 0.35. For ethyl β‐ethoxyacrylate, copolymerization with styrene and acrylonitrile indicates Q = 0.015 and e = 0.3. Both substituted vinyl lethers showed a much lower reactivity (Q factor) than expected. The decreased resonance interaction in these molecules was further supported by infrared data. Attempts to prepare β‐chlorovinyl methyl ether by three different methods were unsuccessful.
Report on molecular‐weight measurements of standard polystyrene samples. II. International union of pure and applied chemistry
Authors: Frank H. P. , Mark H. F.
Published: April 2003

As an extension of our original program, one more polystyrene fraction was investigated in numerous laboratories by means of viscosimetry, osmometry, light scattering, and ultracentrifuge. The various results are compared and critically discussed. Possible explanations and suggestions for improvement are offered in those cases in which considerable discrepancies occur. The viscosity results show satisfactory agreement. The discrepancies among osmotic results are believed to be due largely to unsatisfactory performance of the so‐called semipermeable membranes. Discrepancies among light‐scattering results can mostly be traced back to the unsatisfactory state of the various calibration techniques. The results obtained with the ultracentrifuge agree quite satisfactorily.