bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular weight dependence of the intrinsic viscosity of polymer solutions. II
Authors: Krigbaum W. R. , Flory P. J.
Published: April 2003

Intrinsic viscosities of polystyrene and polyisobutylene fractions in good and in “ideal” solvents have been examined from the point of view of their dependence on molecular weight. A compilation of results is presented which covers exceptionally wide ranges, from several thousand to several to million, in molecular weight. The intrinsic viscosity in an “ideal” solvent (i.e., cyclohexane at 34°C. for polystyrene, or benzene at 24° for polyisobutylene) is remarkably well fitted over the molecular weight range cited above by the relation:

where K is a constant, independent of molecular weight, for a particular polymer at a given temperature. The molecular expansion factor α3 which applies in good solvents (e.g., toluene for polystyrene and cyclohexane and diisobutylene for polyisobutylene) as calculated from:

increases with molecular weight approximately in accordance with the relationship:

However, the quantity (α5 − α3)/M1/2 changes appreciably with M in some cases. This is particularly true for molecular weights below 50,000. Results of an examination of the effect of rate of shear on the viscosity of polystyrene in benzene at 25° and in cyclohexane at 34°, and of the intrinsic viscosity‐molecular weight relation for polystyrene in benzene at 25°, are reported.
A method for studying crosslinking in addition polymerization
Authors: Alfrey Turner , Berdick Murray
Published: April 2003

Vinyl acetate has been copolymerized with small amounts of the diallyl ester of dithiodiglycolic acid (DADT). A method has been devised for the reduction of the disulfide crosslinks to sulfhydryl groups by means of thioglycolic acid under mild conditions, thereby enabling the recovery of the primary molecules of the original polymers. The method has been applied both to soluble copolymers (made with the lowest concentrations of DADT) and to insoluble space‐network copolymers (made with slightly higher concentrations of DADT). The polymers have been characterized before and after reduction by viscosity determinations. The reduction process had only a negligible effect on the viscosity of poly(vinyl acetate). The rate of reduction was diffusion controlled not only in the case of the gels, but apparently also in cases where soluble polymers were made with amounts of DADT less than necessary for gelation at high conversion. The DADT acted not only as a crosslinking agent, but also as a chain transfer agent. The method is suggested as potentially useful in developing the theory of three dimensional polymerization, and in studying the properties of space‐network polymers.
Studies on heat deterioration of specially prepared natural rubber vulcanizates
Authors: Metz Donald J. , Mesrobian Robert B.
Published: April 2003

Natural rubber has been vulcanized to varying degrees of crosslinkage through the use of decamethylene dismethyl azodicarboxylate. The effect of degree of crosslinkage on extent of heat deterioration is demonstrated. Studies are also presented on the beneficial or deleterious action on heat deterioration of various chemical agents incorporated in the free state into natural rubber vulcanizate.
Influence of temperature of polymerization on the structural composition of emulsion polymers of butadiene
Authors: Condon F. E.
Published: April 2003

This report assembles and correlates published data relating to the effect of temperature of polymerization on the structural composition of butadiene polymers, that is, on the relative percentages of polymer double bonds, derived from butadiene, in the 1,2 (vinyl), trans‐1,4, and cis‐1,4 configurations. The data support, and are not in conflict with, the following conclusions: (1) The percentages of vinyl, trans, and cis double bonds in emulsion polymers of butadiene are determined primarily by the temperature of polymerization in the fundamental way that is characteristic of systems of simultaneous competing reactions. (2) Other environmental features, such as type of recipe, and including the presence of a comonomer, e.g. up to 29% of styrene, have comparatively little effect on the relative amounts of vinyl, trans, and cis double bonds. (3) Differences in the physical properties of emulsion polymers of butadiene prepared at the same temperature probably must be attributed to differences in structure other than differences in the relative proportions of vinyl, trans, and cis double bonds, such as the average molecular weight, the molecular weight distribution, and the presence of a comonomer. It is shown that a maximum in the percentage of vinyl double bonds, previously indicated by experiment but attributed to gelation, is inherent to this system of three simultaneous competing modes of polymerization.
Second approximation calculations of mechanical and electrical relaxation and retardation distributions
Authors: Williams Malcolm L. , Ferry John D.
Published: April 2003

Second approximation methods for calculating distribution functions of mechanical relaxation times from complex dynamic data have been improved so that calculations of adequate accuracy can be made over a wider range of variables than was previously possible. Analogous methods for calculating distribution functions of mechanical retardation times and electrical relaxation times are given. The numerical values of the required second approximation correction factors are tabulated.
Gutta. I. Single crystals of alpha‐gutta
Authors: Schlesinger Walter , Leeper H. M.
Published: April 2003

Gutta, the polyisoprene hydrocarbon obtained from gutta percha or balata, is usually considered to differ from rubber in that gutta is a trans‐isomer and rubber a cis‐isomer of polyisoprene. Most of the data on the basis of which these structures have been assigned come from x‐ray diffraction pictures of polycrystalline polymer. Single crystal data have not been published, although such data would provide more detailed information. Chicle gutta has been shown to be a lower molecular weight modification of gutta from gutta percha. As a consequence of its lower molecular weight chicle gutta is a granular, free‐flowing powder, whereas gutta percha gutta is horny and tends to clump together. Because of its physical characteristics and lower molecular weight, chicle gutta was used first in an attempt to grow single crystals of gutta. By working with dilute solutions, well‐shaped single crystals of chicle gutta as large as 0.35 mm. in the long direction were obtained. From gutta percha Pahang, crystals 0.10 mm. long were isolated. Crystals could be grown either by slow diffusion of solvent or by cooling a supersaturated solution. Crystals were found to be optically anis tropic and to exhibit parallel extinction when examined under crossed Nicols with the polarizing microscope. Crystals obtained were of the alpha modification of gutta.
Texture of some crystalline synthetic polymers by electron microscopy
Authors: Cooper A. C. , Keller A. , Waring J. R. S.
Published: April 2003

The importance of sample preparation is demonstrated with examples of techniques based on (1) evaporation in vacuo, (2) casting from solvent or solvent mixtures, (3) ultrasonic disintegration. Attention is drawn to the “sheaf‐like” arrangement of the microfibrils and to other aspects of the texture. There is evidence of periodicities, but these are considered to vary with the preparation, and may be a consequence of the helical arrangement and “rope‐like” character of the bundles of microfibrils or of a tendency to form a woven texture.
Uncertainties in measurement of osmotic pressure of polymer solutions
Authors: Cleverdon D. , Laker Mrs. D. , Smith P. G.
Published: April 2003

For a particular sample of polystyrene, different osmometric estimates of Mn have been reported. The possibility that the difference is due, in the one case, to permeation of the membrane by low molecular weight polymer has been carefully considered. It is shown that this can not be the explanation. The difference is in some way associated with chemical differences in the membranes used. Apart from these considerations of error, the significance of the number‐average molecular weights of the unfractionated polymers of commerce is shown to be more acutely dependent upon the detail of the low molecular weight end of the distribution than may be realized. The present calculations are based upon a realistic estimate of the low molecular weight polymer content of commercial polymers.
Gutta. II. Interconversion of alpha and beta forms
Authors: Leeper H. M. , Schlesinger Walter
Published: April 2003

The gutta isolated from chicle has been demonstrated to be structurally identical with trans‐polyisoprene from gutta percha and balata but has a molecular weight of 16,000–18,000, about one‐half that of the latter two polymers. Its ease of purification and marked crystalline behaviour suggested its use in a study of gutta polymorphism.

The α‐and β‐forms of chicle gutta were prepared and their identities were established by means of x‐ray diffraction measurements and melting properties. The degree of crystallinity and internal molecular strain were shown to affect the melting points of the two forms of gutta through wide ranges. Interconversions of α‐and β‐guttas were effected by means of heat conditioning, solution and reprecipitation, melting and resolidification, and treatment of the gutta with nonsolvents. Dilatometric data were used to describe the change of specific volume when β‐gutta was converted to α‐gutta in a conditioning bath as the temperature was increased stepwise from 30°C. to 80°C. at the rate of 1°C. per hour. The discontinuous, saw‐toothed nature of the specific volume vs. time curve was rationalized on a basis of reactions involving changes in degree of molecular order and relief of strain within the gutta. The curve suggested the following gross reactions: 30–36°C., thermal expansion of β‐gutta of low crystallinity; 36–52°C., increase in degree of crystallinity of β‐gutta; 52–60°C., melting of β‐gutta; 60–64°C., transition of β‐ to α‐gutta; 64–72°C., melting of α‐gutta; 72–80°C., thermal expansion of molten gutta. α‐Gutta, in the melted condition, was shown to undergo a transition, above 72°C., to a form whose stereo identity has not yet been established. The rate of transition from β‐to α‐gutta at temperatures at which α‐is the stable form, appeared to be hastened in the presence of certain liquids.
Chain transfer in the peroxide catalyzed polymerization of styrene
Authors: Kapur S. L.
Published: April 2003

The chain transfer constants of twelve solvents have been determined for the peroxide catalyzed polymerization of styrene and are compared, where possible, with those for methyl methacrylate. The values found are discussed in relation to structure and activity.
Kinetics of chlorotrifluoroethylene polymerization
Authors: Thomas W. M. , O'Shaughnessy M. T.
Published: April 2003

An exploratory investigation of the kinetics of the polymerization of chlorotrifluoroethylene (I) has been made. Experiments were conducted in bulk, in solution in several solvents, and in the presence of several comonomers. Acetyl peroxide (II) was found to be the most effective of common initiators and was used in most of the experiments. The sealed empoule technique was employed. The bulk polymerization of I is zero order to 60–80% conversion; the rate varies as the 0.7 to 0.8 power of the acetyl peroxide concentration, and the over‐all activation energy is 17 kcal./mole. The solution polymerization in benzene appears to be first order in monomer; in other solvents the order was not ascertained. The rate and activation energy in solution are solvent dependent and there appears to be an inverse relationship between the rate of polymerization of I in a solvent and the rate of decomposition of II in that solvent. The rate of decomposition of II was measured in a number of solvents and found to vary widely and to parallel, roughly, the rate of decomposition of benzoyl peroxide. The polymerization rate of I in solution is also c. 0.7 order in acetyl peroxide, but was 0.5 order in Porofor N in limited experiments. From copolymerization experiments with styrene, vinyl acetate and methyl methacrylate values of Q of 0.025, 0.025, and 0.016, and of e of 1.4, 2.0, 1.4, respectively, were inferred, in the Q–e scheme of Alfrey and Price. These results above are discussed in the light of polymerization theory.
Rates and activation energies of thermal degradation of styrene and acrylate polymers in a vacuum
Authors: Madorsky S. L.
Published: April 2003

A study was made of rates and activation energies of thermal degradation of polymeta‐methylstyrene, poly‐alpha‐deuterostyrene, poly‐alpha‐methylstyrene, and hydrogenated polystyrene, in the styrene type of polymers; and of two methyl methacrylates and one methyl acrylate, in the acrylate type of polymers. This study was carried out in the temperature range 240–355°C., by measuring rates of loss of weight of the samples, due to volatilization, by means of a very sensitive tungsten spring balance enclosed in a vacuum. The samples were limited to 5–6 mg. to avoid spattering. The activation energies were obtained by plotting the logarithms of the initial rates, against the inverse of absolute temperature. The styrene polymers, except hydrogenated polystyrene, degrade thermally chiefly into monomeric type molecules. The activation energy of these polymers is about the same as for polystyrene, which is 58 kcal. In the case of hydrogenated polystyrene, breaks in the chain occur at random, the same as in polyethylene. The activation energy is 52 kcal. Polymethyl methacrylate, like the styrene polymers, breaks mostly at the radical chain ends, yielding the monomer. The activation energy is 33 kcal. for a benzoyl peroxide polymerized, 150,000 MW polymer and 55 kcal. for a thermally polymerized, 5,100,000 MW polymer. Polymethyl acrylate follows a mechanism of random breaking of the chains, and the activation energy is 37 kcal.
Solubility and molecular size distribution of crosslinked polystyrene
Authors: Charlesby A.
Published: April 2003

Polystyrene, in common with a number of other long chain polymers, can be crosslinked by exposure to high energy radiation, the degree of crosslinking being directly proportional to the radiation dose. Measurements were made of the solublity in benzene and toluene, as a function of degree of crosslinking. A theoretical derivation is given for the sol fractions of a long chain polymer as a function of the crosslinking index γ, assuming that the initial molecular size follows a Poisson (random probability) distribution. The relationship between s and γ is shown to be:

According to this formula a gel forms if γ> 0.5. An extension to deal with the possibility of chain fracture is described. A comparison of the observed solubility curve with this formula, and with that given by Flory for a uniform initial molecular size shows that only the former agrees with the experimental data. Little or no chain fracture occurs due to adiation.
Swelling properties of polystyrene crosslinked by high energy radiation
Authors: Charlesby A.
Published: April 2003

Polystyrene has been crosslinked by atomic pile radiation, the degree of crosslinking being proportional to the radiation dose. The swelling properties of the crosslinked polymer have been studied as a function of degree of crosslinking γ. There is found a relationship of the form required by theory: V5/3 ∝︁ 1/γ, V being the volume swelling ratio. This formula fails at low degrees of crosslinking. A fuller investigation shows that a number of corrections must be applied, taking into account gel fraction, distribution of molecular weight, and crosslinking index in the gel, etc. On the assumption that the initial molecular weight follows a Poisson distribution, good agreement is obtained between the fuller theory and observed data. The number‐average molecular weight is between 1.53 × 105 and 2.14 × 105. The relationship between γ and radiation dose R is also obtained, and is identical with that deduced previously by entirely different means from solubility data. Pile radiation provides a means of producing polymers with accurately known crosslinking index. The energy required to produce a crosslink in polystyrene by high energy radiation is much greater than in many other linear polymers.
Liquid polyacrylates
Authors: Leonard F. , Szlachtun A. J. , Cort I.
Published: April 2003

Liquid polymers of ethyl, n‐butyl, and 2‐ethylhexyl acrylates were prepared using an anionic initiating system. Liquid polyethyl acrylate was tested as a plasticizer in a stabilized and unstabilized polyvinyl chloride plastisol composition. In the unstabilized composition, fused samples were obtained which were comparable in color to a di‐2‐ethylhexyl phthalate (DOP) plasticized polyvinyl chloride sample prepared under the same conditions. Stress–strain tests on stabilized films indicated that with liquid polyethyl acrylate as the plasticizer a film was obtained showing higher tensile strength, yet equivalent ultimate elongation as compared to a similarly prepared DOP plasticized composition.
Free diffusion with coefficient dependent on concentration
Authors: Gillis J. , Kedem Orah
Published: April 2003

An approximate solution is obtained for the nonlinear diffusion equation in which the coefficient of diffusion is a linear function of the concentration. Methods are developed for deducing the relevant parameters from experimental data and of constructing theoretical curves from these parameters. The results are illustrated by a worked example.
Configuration and optical activity of vinyl polymers
Authors: Frisch H. L. , Schuerch C. , Szwarc M.
Published: April 2003

It is obvious that the starred carbon atoms in vinyl polymers of the type exist in two distinct steric configurations which are denoted here by symbols + and −. It is shown that the existence of these configurations leads to the formation of different types of polymers; however, no simple relation correlates the optical activity of such polymers with the relative distribution of + and − configurations along the polymeric chain. The various possible structures are discussed in some detail. The kinetics of such polymerizations initiated by an optically active catalyst are treated by statistical methods.
Viscosity and streaming birefringence in the nonlinear concentration range of macromolecular solutions
Authors: Peterlin Anton
Published: April 2003

From the close correlation between viscosity increment and streaming birefringence in dilute solution the parallelity of both effects in concentrated solutions is deduced and proved by the results on nitrocellulose, polystyrene, and polyisobutylene samples. By plotting birefringence vs. (η − ηl)q and the extinction angle vs. (η − ηl)q/c, the optical anisotropy and the stiffness of the single macromolecule can be obtained from measurements at fairly high concentrations, where the effects are large and therefore easily accessible.
Thermodynamics of crystallization in high polymers. Cellulose trinitrate
Authors: Flory P. J. , Garrett R. R. , Newman S. , Mandelkern L.
Published: April 2003

Melting temperatures of cellulose trinitrate (13.96% N) in mixtures with γ‐butyrolactone have been determined dilatometrically, and also by an optical method depending on depolarization of polarized light when transmitted through a semicrystalline sample. Results obtained by these two methods, and also by direct visual observation, are in good agreement. Whereas the dilatometric method is preferred for higher concentrations of diluent (volume fraction v1 = 0.86 to 0.68) where the melting point is below 80°C., gas generation by decomposition necessitated abandonment of this method at the higher melting temperatures for lower diluent concentrations. Adoption of the optical method permitted determination of melting temperatures as high as 116°C. (v1 = 0.60). The results have been treated according to the thermodynamic theory of melting of polymers. While the results do not extend far enough to allow definite assignment of the melting point T of the pure polymer, they indicate that it is at least 1000°K. The heat of fusion per structural unit is low—not over 1500 cal. per repeating unit, or 5 cal./g. The low value of the entropy of fusion—less than 1.5 cal./deg./mole of units–indicates limited flexibility of the chains in the liquid state. The high melting point of cellulose trinitrate is a consequence of its low entropy of fusion, and cannot be attributed to large intermolecular attractions in the crystal.
The excluded volume of branched chains
Authors: Kreussling F. , Ullman R.
Published: April 2003

A theory of the excluded volume of branched molecules has been developed. The model of the branched molecule is a main or backbone string of beads from which side branches (which are themselves unbranched) originate. Each of these beads has the property of the Kuhn statistical chain element. The calculation is based on the Fokker‐Planck equation as used by Hermans and collaborators. The differential equation obtained therefrom is not solved, but the average squared distance between two segments on the main chain is obtained. It is found that this quantity \documentclass{article}\pagestyle{empty}\begin{document}$ < r_{t_p }^2 > _{Av} $\end{document} contains a term proportional to (t − p)3/2 power, which term arises from the contribution of the branches. The radius of the molecule, which can be measured by light scattering techniques, contains a term proportional to the molecular weight to the three halves power if the length of the branches does not depend on molecular weight. It is suggested that the dependence on molecular weight of the relation between molecular size and branching could be used as an experimental check of the theory.
The sedimentation and diffusion of sodium polymethacrylate and polymethacrylic acid
Authors: Howard G. J. , Jordan D. O.
Published: April 2003

The sedimentation constants and diffusion coefficients of sodium polymethacrylate and of polymethacrylic acid have been determined at various concentrations of polymer and of added electrolyte and the nature of the charge effects is considered. A ratio y = (molarity of added electrolyte)/(grundmolarity of polymer) is used to obtain S20 at y = ∞ when the polyelectrolyte is assumed to be uncharged. The variation of the effective radius with y is considered not to be due to asymmetry but to the open network nature of the polyelectrolyte coil.

The sedimentation constant of unionized polymethacrylic acid is determined and also the variation of sedimentation constant with degree of ionization.
Improvement of the dirt suspending power of CMC
Authors: Nieuwenhuis K. J.
Published: April 2003

The salts of carboxymethylcellulose (CMC) are used in large quantities to improve the dirt‐suspending power of synthetic detergents and soaps. Hardly any attention has been given to the question as to which properties they should have to obtain the greatest suspending power. They exert their specific influence because they are adsorbed by cellulose fibers from their solutions in water. Theoretical considerations are given, showing that: (1) The degree of substitution (DS) should probably be about 0.5. (2) The substitution should be as uniform as possible. (3) The cellulose chains should be neither too short nor too long. Normally only the average degree of substitution, DS, is determined. The fiber contents, FC, i.e., the percentage of insoluble and partly swollen fibers in 1/20 N NaOH can be taken as a measure of the uniformity of the substitution. Technical products differ greatly in pH and salt contents; therefore the viscosity of solutions of the technical products containing 1% of the cellulose ether, to which 2.5% Na2CO3 and 2.5% NaHCO3 have been added, is taken as a measure of the length of the cellulose chains. The easiest way to obtain uniformly substituted products is by dispersing cellulose and reagents in a suspending liquid, e.g., an alcohol or a hydrocarbon. FC's smaller than 2 to 4% are obtained. Then the dirt‐suspending power was greatest with a DS between 0.48 and 0.53; and a viscosity measured as above with a Hoeppler standard viscometer between 11 and 29 c.p.s. The substitution in general is much less uniform when CMC is prepared according to the customary method by mixing cellulose, NaOH, and ClCH2COONa or ClCH2COOH and a little water. Then the results were best with an average DS between 0.51 and 0.60, and an FC between 6 and 16%, said viscosity being 20 to 30 c.p.s.
Configuration of certain protein molecules. An inquiry concerning the present status of our knowledge
Authors: Edsall John T.
Published: April 2003

It is now becoming possible to correlate studies on the general size and shape of protein molecules in solution with knowledge of the possible configurations of polypeptide chains and, in some instances, with that of the actual sequence of amino acid residues in these chains. The formation of helices and of “pleated sheets” from polypeptide chains, and the dimensions of these structures, are discussed, and the possible significance of proline residues for the bending and folding of chains is pointed out. The relation of purified protein preparations to the state of the proteins in their natural surroundings is discussed, as is the meaning of the concept of purity. Protein molecules are to be regarded as highly ordered and regular structures, but probably not as completely rigid. The meaning of the concept of protein hydration is considered, with reference to both external and internal hydration. The question of what can be learned from hydrodynamic measurements concerning the hydration and the shapes of protein molecules in solution is critically discussed.

The evidence available today concerning the size and shape of some particularly wellknown proteins is examined. These include beef insulin; horse heart myoglobin; horse hemoglobin; human and bovine serum albumin, including mercaptalbumin; human and bovine fibrinogen; rabbit myosin; and tobacco mosaic virus. The first three of these molecules are relatively small and symmetrical in shape. Serum albumin appears to be moderately asymmetrical, with an axial ratio of the order of 4 to 1. Fibrinogen, myosin and tobacco mosaic virus are highly asymmetrical. Although the chemical structure of insulin is now known in great detail, the shape of the molecule as a whole cannot yet be precisely specified. All the molecular models proposed for these proteins, except perhaps that for the virus, must be regarded as tentative and subject to revision.

Future prospects of progress in this area are considered, with particular emphasis on the significance of dielectric dispersion, fluorescence polarization, and x‐ray methods. The hope of obtaining fairly rapidly a much deeper insight into protein structure now appears justifiable.
Theory of ionic absorption on wool keratin
Authors: Olofsson Bertil
Published: April 2003

At low pH wool behaves as an anion exchanger. The equilibrium constant for absorption of Cl− and SO4−2 in mixtures has been determined and used for a statistical control of theoretical constants. It is demonstrated that the Donnan theory is not applicable. The reason for this is the existence of a nonvanishing difference in standard thermodynamic potential (Δμ) between liquid and fiber phase. If a theory considering adsorption on localized sites is used (Gilbert‐Rideal) and the Δμ‐value is associated with adsorption energy it is found that the energy of Cl− and SO4−2 adsorption is comparable to the energy of water absorption on fibers. The consequences for the general application of the Donnan theory are discussed.
Partial specific volume of the protein and water in beta‐lactoglobulin crystals
Authors: McMeekin T. L. , Groves M. L. , Hipp N. J.
Published: April 2003

The densities and water contents of large β‐lactoglobulin crystals were determined as a function of relative humidity. When the specific volumes of the crystals (1/density) were plotted against their water contents, a straight line was obtained between 14 and 46% water. The extrapolation of this line by the graphical intercept method of Lewis and Randall gave a value of 0.772 for the specific volume of the protein and 0.983 for the specific volume of the water in the β‐lactoglobulin crystal. Subtracting the specific volume of the protein in the crystal from the specific volume of the anhydrous protein (0.802–0.772) gave a value of 0.030 ml. for the contraction of one gram protein on becoming hydrated.

A value of 0.021 ml. was calculated for the contraction of water per gram protein by the difference between the apparent specific volume of the protein in solution, assuming water to have a specific volume of 1.003, and the value of 0.772 for the specific volume of the protein in the crystal. There was good correlation between the value for contraction of water as calculated from the ionic groups of the protein and the observed contraction value.
The termination reaction in radical polymerizations. Polymerizations of methyl methacrylate and styrene at 25°
Authors: Bevington J. C. , Melville H. W. , Taylor R. P.
Published: April 2003

Styrene and methyl methacrylate have been polymerized at 25° using α,α′‐azo‐bis‐isobutyronitrile labeled with C14 as initiator. The numbers of initiator fragments per polymer molecule have been determined by measurements of the average molecular weights of the polymers by osmometry and the specific activities of the polymers and the initiator by gas counting. It is found that polystyrene radicals combine at 25° and that for polymethyl methacrylate radicals at this temperature disproportionation occurs about twice as frequently as combination.
Developments in the theory of cationic polymerization. Part II
Authors: Plesch P. H.
Published: April 2003

Olefins can only be polymerized by metal halides if a third substance, the cocatalyst, is present. The function of this is to provide the cation which starts the carbonium ion chain reaction. In most systems the catalyst is not used up, but at any rate part of the cocatalyst molecule is necessarily incorporated in the polymer. Whereas the initiation and propagation of cationic polymerizations are now fairly well understood, termination and transfer reactions are still obscure. A distinction is made between true kinetic termination reactions in which the propagating ion is destroyed, and transfer reactions in which only the molecular chain is broken off. It is shown that the kinetic termination may take place by several different types of reaction, and that in some systems there is no termination at all. Since the molecular weight is generally quite low, transfer must be dominant. According to the circumstances many different types of transfer are possible, including proton transfer, hydride ion transfer, and transfer reactions involving monomer, catalyst, or solvent.
Zur frage der anionpolymerisation, II. Die addition von Äthylenoxyd an phenol
Authors: Patat F. , Cremer E. , Bobleter O.
Published: April 2003

Die Anlagerung von Äthylenoxyd an Phenol wird quantitativ beschrieben. Die Reaktion geht über die “Anion”‐kette.

u.s.w. So lange noch Phenol vorhanden ist, wird die Polymerisation bei Stufe 2 unterbrochen und nur Glykolmonophenyläther gebildet.
Über den Härtungsmechanismus der äthoxylinharze
Authors: Fisch W. , Hofmann W.
Published: April 2003

Bei der alkalischen Kondensation von Epichlorhydrin mit zweiwertigen Phenolen entstehen Hydroxyl‐ und endständige Oxydogruppen enthaltende aliphatisch‐aro‐matische Polyäther. Die Umsetzung derartiger Reaktionsprodukte mit Dikarbonsäureanhydriden führt zu hochvernetzten wertvollen Massen. Der Härtungsmechanismus wird in der Anfangsphase an einem technischen Produkt und über den ganzen Reaktionsverlauf an geeigneten Modellreaktionen analytisch verfolgt. Es zeigt sich, dass sowohl Diester‐ wie auch Ätherbrücken als Vernetzungselemente auftreten.
Reversible gelation of concentrated polyacrylonitrile solutions
Authors: Bisschops J.
Published: April 2003

The reversible gelation of concentrated polyacrylonitrile solutions was studied by creep measurements under constant shearing stress at different stages of the reaction. The pure viscous 20% solution in dimethyl formamide were apparently stable at 25°C. When they were cooled down below 0°C. a retarded elasticity appeared and the solutions became completely elastic gels after a certain time. The rate of gelation increased strongly as the temperature decreased. Furthermore, when the gels were heated back to 25°C. the gelation process continued after a short melting period. A simple empirical equation describes the creep of the gels in the completely elastic state and the results are discussed in terms of a generalized Maxwell model. The gelation is to be ascribed to the formation of a tridimensional network. The crosslinks are assumed to be crystallization nuclei.
Viscosities of dilute aqueous solutions of a partially quaternized poly‐4‐vinylpyridine at low gradients of flow
Authors: Eisenberg H. , Pouyet J.
Published: April 2003

The viscosity of a partially (60.8%) quaternized polyvinylpyridine with n‐butyl bromide has been investigated in dilute‐water and sodium chloride solutions, in a rotation (Couette) viscometer, at low gradients of flow. It was possible to extrapolate the ηsp/c against concentration plot in water by working at very low concentrations of the polymer. At about 5 × 10−5 g./ml. the curve reaches a maximum and decreases sharply upon dilution to about one‐sixth the value at the maximum. The shape and size of the equivalent ellipsoid corresponding to the 60.8% polyvinylpyridinium bromide (DP = 7660) ions was estimated from the limiting viscosity number ([η] = 9500 ml./g.) and birefringence (extinction angle) data. The length of the stretched molecule was estimated to be 7420 A., corresponding to < half the hydrodynamic length of the extended macromolecule. Extrapolations in sodium chloride solutions have been obtained at constant concentrations (up to 10−3 M) of the simple electrolyte. Small amounts of added simple electrolyte decrease the viscosity numbers in solutions at finite concentrations of the polymer to a large extent, whereas the limiting viscosity numbers are affected to a far smaller degree. This phenomenon has qualitatively been attributed to the pronounced decrease in the intermacromolecular electrostatic interactions at finite concentration of the polymer upon the addition of a relatively small amount of mobile electrolyte; at the same time the intramacromolecular interactions are affected to a much smaller extent.
Solubility of gases and vapors in crosslinked polymers
Authors: Frisch H. L. , Stannett V.
Published: April 2003

The sorption isotherms proposed by Barrer have been modified in two ways. First, the theory has been extended to apply to the sorption behavior of crosslinked polymers by including a contribution to the free energy of the elastic stretching of the network in accordance with the findings of Flory and Rehner. Second, the effect on the sorption isotherm of a concentration dependent heat of dilution has been investigated. Both these corrections may lead to the appearance of a two‐valued sorption isotherm.
Applied force and second order transitions of rubber
Authors: Wall F. T. , Miller Donald G.
Published: April 2003

The second order transition temperatures of three different cures of natural rubber have been studied as functions of elongation by observing length dependence on temperature. This transition temperature (Tm) decreases with increasing applied force, and at any given force increases with increased crosslinking; moreover the slopes of the Tm vs. force curves become less steep with increased crosslinking. The results are in agreement with the following propositions: (1) that transitions are caused by the onset of rotations; (2) that extension of the polymer makes the onset of such rotations easier, thus lowering Tm; (3) that increased crosslinking hinders rotation so as to increase Tm; and (4) that increased crosslinking diminishes the effect of a given force on Tm. The hypothesis of rotation is also discussed in connection with the effect of swelling agents on the second order transition.
An X‐ray study of the decomposition product of the ethylamine‐cellulose complex
Authors: Segal Leon , Loeb Leopold , Creely Joseph J.
Published: April 2003

The present paper reports the results of a study of the decomposition product of the ethylamine‐cellulose complex obtained from cotton cellulose. It is shown that the cotton remaining after removal of ethylamine by distillation possesses a crystalline component identical with the ammonia‐cellulose decomposition product designated by other workers as cellulose III. Certain important differences between ramie cellulose III and cotton cellulose III are discussed especially as regards the relative ease of recoversion to cellulose I. Experimental data are given showing the effect on degree of conversion of temperature, and of two different times of immersion in boiling water. Data are also given showing the effect on the structure of the decomposition product of time of immersion in ethylamine. An attempt is made to explain the appearance of a strong diatropic 020 interference in the x‐ray patterns of the decomposition product and of the regenerated cotton cellulose I.
The microstructure of diene polymers. I. Polyisoprenes and polybutadienes prepared at high temperatures
Authors: Richardson W. S.
Published: April 2003

Polybutadienes and polyisoprenes prepared by bulk thermal polymerization at temperatures between 100 and 250°C. have been analyzed for the percentages of the various types of addition present. It is found that polybutadiene tends toward a mixture of about 40% each of cis‐1,4‐ and trans‐1,4‐ and 20% 1,2‐addition as the polymerization temperature is increased. Polyisoprenes show a decrease of 1,2‐addition and cis‐1,4‐addition and a corresponding increase in trans‐1,4‐ and 3,4‐addition at preparation temperatures above about 100°C. Differences in energy and entropy of activation for the formation of the various structures in polybutadiene are given.
The structure of neoprene. VI. Crystallization
Authors: Maynard J. T. , Mochel W. E.
Published: April 2003

A volume dialometric study of the crystallization behavior of polychloroprenes made at −40°, 10°, and 40°C. has shown that the melting point of the crystalline phase in these polymers is an inverse linear function of polymerization temperature. Polychloroprene made at −40°C. melts at ca. 65°C., while conventional 40°C. neoprenes melt at ca. 40°C. Comparison of this data with the melting point depression observed in a chloroprene/methacrylonitrile copolymer and in polychloroprene/diluent mixtures has made possible calculations which confirm earlier hypotheses that neoprenes have a highly regular structure. Commercial neoprenes made at 40°C. are calculated to consist of 80–85% of the trans‐2‐chloro‐2‐butylene units which result from trans‐1,4 polymerization of chloroprene. Densities determined for crystalline and amorphous neoprenes have been used to calculate the degree of crystallinity of these polymers, and this information has made possible calibration of the infrared crystallization‐sensitive bands, for use in measurement of degree of crystallinity. The heat of fusion of the crystalline phase of neoprenes has been found from diluent data to be 22.7 ± 2 calories per gram.
The structure of neoprene. VII. Infrared analysis of configuration
Authors: Maynard J. T. , Mochel W. E.
Published: April 2003

A study of the infrared absorption spectra of polychloroprenes made at temperatures ranging from −40 to 100°C. has made possible identification and estimation of the major structural features of these polymers. It is confirmed that 1,4 polymerization of chloroprene accounts for the greatest part of the structure of all neoprenes, ranging from 99% in −40°C. polymers to ca. 84% in 100°C. polychloroprenes. Of this 1,4 polymer only a small fraction has the cis configuration. This proportion increases from less than 5% in −40°C. polymer to ca. 13% in 100°C. polymer. Small amounts of branched structures that result from 1,2 and 3,4 polymerization are observed. These also increase in concentration with higher polymerization temperatures but do not account for more than 2.5% each even in 100°C. polychloroprenes. The portion of these polymers unaccounted for by these observations amounts at the most to 10% in 100°C. polymers. It is suggested that this part of the structure is that formed by hydrolysis and/or rearrangement of a part of the tertiary allylic chloride units which result from 1,2 polymerization of chloroprene. It is shown that only 50% of an acid‐catalyzed ionic polychloroprene can be accounted for by structures recognized in free‐radical polychloroprenes.
Kinetics of acrylonitrile polymerization in bulk
Authors: Thomas W. M. , Pellon J. J.
Published: April 2003

As a step toward the better understanding of acrylonitrile polymerization a kinetic study was made in bulk with azo and peroxy catalysts over the range 30 to 60°C. Rates were followed gravimetrically in most cases, and molecular weights were estimated from viscosity measurements. Electron micrographs and nitrogen sorption data were obtained. Following a short induction period (which could not be eliminated) polymer separated as a fine suspension, coagulated to form curds at a few tenths percent polymerization and formed a hard, porous mass at about 60% reaction. Product at 5 to 50% polymerization was in the form of dense particles about 0.5 micron across; these appeared to be aggregates of 400 A. particles. The rate of polymerization accelerated up to 1–3% conversion and was then nearly constant to about 50%, beyond which it could not be measured. Rate increased with the 0.8 power of catalyst concentration and showed an over‐all activation energy of 35 to 37 kcal./mole. Molecular weight varied inversely with the 0.2 power of the catalyst concentration, was nearly constant from 5 to 50% conversion and went through a slight maximum with temperature. To account for these observations a kinetic scheme is proposed that involves the possibility of unimolecular chain termination by a process of “burial.” This process is conceived of as a mechanism by which a growing chain may become shielded from further growth by coiling or embedding itself in the solid phase. Equations derived for rate and degree of polymerization fit the data adequately. Consideration is given to the simultaneous effects at high conversion of a small loss in initiator by thermal decomposition, of enrichment of the solution by shrinking liquid volume and of depletion of monomer.
The hydrolysis of cellulose Part I. The fine structure of egyptian cotton
Authors: Sharples A.
Published: April 2003

The kinetics of chain degradation have been studied for the heterogeneous hydrolysis of Egyptian cotton under mild acid conditions. The results have been interpreted to give estimates of accessibilities free from the defects associated with former measurements. The amount of accessible material in the undegraded cotton was found to be 10.8%, but during hydrolysis this is reduced to less than 5%. The recrystallization takes place at an early stage in the degradation, starting at a point when approximately one‐eighth of the intercrystalline chain segments have been broken.
Degradation of long chain molecules by ultrasonic waves. Part V. Cavitation and the effect of dissolved gases
Authors: Brett H. W. W. , Jellinek H. H. G.
Published: April 2003

The rate of ultrasonic degradation of polystyrene in benzene solution saturated with a number of gases was studied. The rate of degradation decreases with increasing solubility of the gas. Ultrasonic degradation is discussed generally on the basis of a theory for ultrasonic cavitation. A rate equation for this type of degradation is proposed. It is concluded that ultrasonic degradation is mechanical in its origin due to the adiabatic collapse of cavities.
Infrared spectrophotometric studies on polyethylene. II. Oxidation
Authors: Rugg Frank M. , Smith Joseph J. , Bacon R. Charles
Published: April 2003

Polyethylene can be heat‐oxidized in air when temperatures in excess of 125°C. are employed or photo‐oxidized when exposed to ultraviolet radiation during weathering. Infrared spectrophotometric studies show that during these types of oxidation carbonyl groups are formed and the concentrations of the three types of carbon to carbon double bond groups present are altered. Grating spectra in the 5.6–6.0 micron region reveal that the carbonyl groups formed by heat‐oxidation are mainly ketonic (5.81 microns) although some aldehyde (5.77 microns) and acid (5.84 microns) groups are also present. In photo‐oxidized samples, the carbonyl groups are rather well distributed among the aldehyde, acid and ketone forms. For oxidized samples showing intense carbonyl absorptions, there is a small increase in the concentration of RHCCHR groups (10.35 microns) for both types of oxidation. At this same degree of oxidation both the heat‐and photo‐oxidized samples show decreases in the concentration of RRCCH2 groups (11.25 microns). However, this decrease is considerably more pronounced in the photo‐oxidized samples. Finally, there is a small decrease in the concentration of RHCCH2 groups (10.07 and 11.00 microns) in the heat‐oxidized samples which stands in contrast to a large increase in concentration of RHCCH2 groups produced by photo‐oxidation. The presence of an absorption maximum at 2.81 microns as the heat‐oxidation of polyethylene is occuring is indicative of unstable hydroperoxide groups.
Relation between the structure of polymers and their dynamic mechanical and electrical properties. Part I. Some alpha‐substituted acrylic ester polymers
Authors: Deutsch K. , Hoff E. A. W. , Reddish W.
Published: April 2003

A comprehensive study of the dynamic mechanical and dielectric properties of acrylic polymers (polymethyl methacrylate, polymethyl‐α‐chloroacrylate) has been made; these two properties were found to be intrinsically correlated; results are given in graphic form. The hypothesis is proposed that each of several mechanical and dielectric dispersion regions found in a given polymer is associated with a definable structural feature, i.e., a group of atoms, in the polymer, such that each group gives rise to a mechanical dispersion and, if polar, also to a dielectric dispersion in the same temperature and frequency region; it should also be possible to trace the same dispersion from one polymer to another, provided they all contain the same group.
A new method for the determination of branching in polymers
Authors: Hayes Robert A.
Published: April 2003

The transfer constant for the butadiene‐polybutadiene system at 50°C. has been calculated from data obtained from a graft polymerization study of that system. This constant (K = 1.1 × 10−3) has been used to calculate that polybutadiene prepared in an emulsion system at 50°C. contains an average of one branch for every 800 monomer units.
Calculation of extrusion behavior of viscoelastic materials from the relaxation distribution function
Authors: Smith Thor L.
Published: April 2003

A viscoelastic material when extruded rapidly through a short capillary or spinneret may exhibit an effective viscosity which is smaller than the usual or zero shear rate viscosity by a factor of several hundred. An equation is derived which expresses the effective viscosity as a function of the time the material spends in the spinneret (transit time) and the distribution function of Maxwellian relaxation times. It is assumed that the mechanical properties of the material may be represented by a generalized Maxwell model. Effective viscosities observed when a 25% cellulose acetate solution in a 96:4 (by weight) acetone:water solvent is extruded through a spinneret with radius 0.006 cm. and effective length 0.0186 cm. are given. The relaxation distribution function for the cellulose acetate solution is calculated from the dynamic viscosity data of Philippoff. From the distribution function and values of the transit time, effective viscosities are calculated and found to differ from the experimental values by −26 to 60%. In view of the fact that the effective viscosities are smaller than the zero shear rate viscosity by factors ranging from 145 to 10.8, the agreement between calculated and experimental values is quite satisfactory.