bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of chlorotrifluoroethylene polymerization
Authors: Thomas W. M. , O'Shaughnessy M. T. 
Published: April 2003

AbstractAn 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

AbstractA 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

AbstractPolystyrene, 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

AbstractPolystyrene 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

AbstractLiquid 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.
Configuration and optical activity of vinyl polymers
Authors: Frisch H. L. , Schuerch C. , Szwarc M. 
Published: April 2003

AbstractIt 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

AbstractFrom 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

AbstractMelting 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractIt 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

AbstractAt 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

AbstractThe 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

AbstractStyrene 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

AbstractOlefins 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

AbstractDie 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

AbstractBei 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.