bluuebunny/crossref_metadata_2025_split huggingface dataset:
The termination reaction in radical polymerizations. II. Polymerizations of styrene at 60° and of methyl methacrylate at 0 and 60°, and the copolymerization of these monomers at 60°
Authors: Bevington J. C. , Melville H. W. , Taylor R. P. 
Published: April 2003

AbstractStyrene has been polymerized at 60° and methyl methacrylate at 0 and 60° using 2,2′‐azo‐bis‐isobutyronitrile labeled with C14 as initiator. The average number of labeled end groups per molecule has been determined for the various polymers and so the relative importances of combination and disproportionation have been assessed. It has been found that polystyrene radicals undergo combination at 60°. In the case of methyl methacrylate, disproportionation occurs about 6 times as frequently as combination at 60° and about 1.5 times as frequently at 0° the activation energy for disproportionation is about 4 kcal. per mole greater than that for combination. The copolymerization of styrene and methyl methacrylate at 60° has been studied by this technique. It is found that when polystyrene radicals interact with polymethyl methacrylate radicals at this temperature combination occurs. The rates of initiation in the copolymerizations have been determined by a new method; the rate of this step is found to be virtually independent of the composition of the monomer mixture.
Effect of molecular weight distribution on gel formation by high energy radiation
Authors: Charlesby A. 
Published: April 2003

AbstractThe effect of exposing long chain polymers to high energy radiation is either to produce crosslinking or chain degradation. Changes in some of the properties are outlined. The formation of gel in many polymers offers a possibility of obtaining information as to the initial molecular weight distribution. Results are given of a mathematical analysis of the amount of gel formed for various degrees of crosslinking. From the shape of the gel crosslinking curve the ratio of z average, z + 1 average etc., to weight‐average molecular weight can be deduced. Formulae for the changes in the molecular weight of the sol are also given.
The reaction of cellulose with acetic acid
Authors: Hiller L. A. 
Published: April 2003

AbstractReaction curves for the reaction of cellulose with acetic acid and water were studied. This reaction was found to be slow and severely limited in extent of reaction. An analysis by means of reaction kinetics equations of this limited reaction led to the following suggested reaction mechanism: (a) The larger fraction of cellulose hydroxyl groups—88% in the particular samples of cellulose investigated—cannot be acetylated because the mutual hydrogen‐bonding between these groups imposes an energy barrier to reaction. This causes the equilibrium constant for the reaction of these groups to be highly unfavorable toward acetylation. (b) Part of the remaining hydroxyl groups (those which do react) react very slowly with a reaction rate apparently dependent on the rate of diffusion of acetic acid into the cellulose fibers. These hydroxyl groups are apparently unassociated hydroxyl groups buried within the cellulose fibers. (c) The remaining hydroxyl groups apparently react according to the kinetics of homogeneous acetic acid acetylation and thus must be in freely accessible locations, such as on the fiber surfaces.
Aromatic polyhydrocarbons. I. Monomer reactions and polymer preparation
Authors: Auspos L. A. , Hall Luther A. R. , Hubbard James K. , Kirk Wm. , Schaefgen John R. , Speck Stanley B. 
Published: April 2003

AbstractPolyhydrocarbons were prepared by the dehydrogenation of 1,4‐dimethyl substituted aromatic hydrocarbons and other related starting materials by several methods. A study was made of the intermediates formed and of their chemical reactions.
Aromatic polyhydrocarbons. II. Chemical and physical properties of polymers
Authors: Auspos L. A. , Burnam C. W. , Hall Luther A. R. , Hubbard James K. , Kirk Wm. , Schaefgen John R. , Speck Stanley B. 
Published: April 2003

AbstractHydrocarbon polymers prepared by the hot tube pyrolytic dehydrogenation of 1,4‐dimethyl substituted aromatic hydrocarbons have been studied and characterized as to chemical and physical properties. Tough, chemically resistant products were obtained, but fabrication of these polyhydrocarbons was difficult due to the relative intractability of the polymers obtained.
Polyelectrolyte gels in salt solutions
Authors: Katchalsky A. , Michaeli I. 
Published: April 2003

AbstractEquilibrium swelling and salt accumulation were investigated for highly swollen polymethacrylic acid gels in aqueous salt solutions of 0.8 × 10−2 to 0.5 M LiCl, NaCl, and KCl, at varying degrees of ionization of the polymer. The same equilibrium results were obtained with all three cations, thus showing that in the range investigated, specific interactions between the cations and the polyacid network may be disregarded. It was shown that the Donnan distribution, uncorrected for activity factors, cannot be applied to highly charged, highly swollen gels, even as a rough approximation. A general theory was developed which satisfactorily describes these equilibrium results in the entire ionization range of the gel in salt solutions up to 0.5 M. This theory was based on Flory's equation for the contractile free energy of the network, and on the equation of Katchalsky et al. for the electrostatic free energy of polyelectrolyte solutions. It was found that the activity factor of the salt in the gel‐phase is chiefly determined by the electrostatic factor, and closely approximates the activity factor in polyelectrolyte solutions.
A molecular weight–intrinsic viscosity study of several diene polymers
Authors: Pollock D. J. , Elyash L. J. , DeWitt T. W. 
Published: April 2003

AbstractAn intrinsic viscosity‐molecular weight study has been made of several polybutadienes and synthetic polyisoprenes. The Fox‐Flory treatment of such data was applied in each case. This serves for the determination of a constant characteristic only of the polymer and related to the unperturbed end‐to‐end distance of the polymer chain. A comparison of the dependence of this constant on polymer structure with that predicted theoretically shows good agreement. A further comparison of the values of this constant for the synthetics with those for natural polyisoprenes leads to the conclusion that the diene polymers, natural and synthetic, do not differ markedly in hindrances to free rotation.
Pyrolysis of α‐ and β‐deuterostyrene polymers
Authors: Wall L. A. , Brown D. W. , Hart V. E. 
Published: April 2003

AbstractRecently the depolymerization of addition polymers has been treated in terms of four elementary reactions: initiation, propagation, transfer, and termination; analogous to those reactions which operate in the polymerization process. It is the transfer process which, according to its relative importance, gives rise to differences in polymers in the monomer yield, in the rate vs. conversion behavior, and in the molecular weight vs. conversion behavior. The transfer process is assumed to operate through the abstraction of a hydrogen from the polymer chain by a radical. By substituting a deuterium for the hydrogen at selected points in the polymer chain, the amount of the transfer process should be decreased due to an isotope effect. Two deuterated polymers were made from α‐ and β‐deuterated styrenes and their depolymerization behavior studied. In the case of the α‐deuterostyrene polymer the results are compatible with a ½ decrease in the rate of the transfer process and also an increase in the rate of the propagation. The results with the β‐polymer imply an increase in both the transfer and propagation rates. The data obtained indicate that in polystyrene the intermolecular transfer process is mainly responsible for the fall in molecular weight of the polymer residue during depolymerization.
Polymerization of methyl methacrylate by pulses of high‐energy electrons
Authors: Majury T. G. 
Published: April 2003

AbstractMethyl methacrylate, vinyl acetate, styrene and diethylene glycol‐bis(allyl carbonate) were subjected to irradiation by very intense microsecond pulses of electrons of 3 MeV energy. The methacrylate underwent a prolonged, slowly decaying polymerization beginning immediately after irradiation; in a typical run, a dose of 1.5 × 105 rep delivered in 12 pulses resulted in 1% polymerization after six hours and 5% polymerization after 50 hours. The extent of polymerization was reduced by increasing the surface of glass in the reaction vessel. Freezing the monomer during irradiation reduced the extent of subsequent polymerization in the liquid state by approximately 40%. Evidence was obtained to show that the polymerizing radicals are of the normal type found in thermal and photochemical work, and their initiation is attributed to the formation of a catalyst during or immediately after irradiation. No significant amount of polymerization took place in the other monomers.
Diffusion of water vapor in polymers
Authors: Long F. A. , Thompson L. J. 
Published: April 2003

AbstractStudies have been made by a sorption‐desorption procedure on the diffusion of water vapor at relative humidities of from 30 to 85% into the polymers, polyvinyl acetate cellulose acetate (37.9% acetyl), cellulose nitrate (12.0% N), 6–10 nylon, and polyvinyl alcohol. Diffusion of water in polyvinyl acetate obeys Fick's law at temperatures of from 30 to 50°C. and also at 22°C., which is below the second‐order transition. The energy of activation for diffusion of water into polyvinyl acetate is 15 kcal. per mole and at 40°C. the diffusion coefficient is 7 × 10−6 cm.2/min. In contrast to the results with organic vapors, the diffusion coefficient for water is found to be independent of concentration of water in the polyvinyl acetate. Similar behavior is found for diffusion of water at 40° into cellulose acetate, cellulose nitrate, and 6–10 nylon. The chief difference is that for these three polymers the diffusion departs mildly from Fick's law at the later stages of some of the sorption and desorption experiments. This generally uncomplicated diffusion of water in these three polymers contrasts with the markedly anomalous diffusion found for organic vapors such as methanol and acetone into cellulose acetate and nitrate. With polyvinyl alcohol the diffusion of water is distinctly anomalous and closely resembles the non‐Fickian diffusion of organic vapors in cellulose acetate and nitrate. One consequence is that the rate of sorption and desorption of water in polyvinyl alcohol is considerably slower than in the other polymers and is also concentration dependent.
Polybenzyl type polymers
Authors: Has Howard C. , Livingston Daniel I. , Saunders Martin 
Published: April 2003

AbstractThe various proposed structures for polymers derived from benzyl type compounds have been discussed and the likelihood of these structures considered in the light of a study of their preparation and properties. Both the para substituted structure of Shriner and Berger and the pendant structure of Henne and Leicester were rejected chiefly on the basis of physical properties, degradation behavior, and x‐ray and infrared evidence. Flory's randomly branched structure also fails to account for the degradation behavior and the infrared spectrum. A new configuration which is a nonrandomly substituted, highly branched molecule is advanced. This structure contains predominantly two types of benzene rings, i.e., a relatively small number of highly substituted rings and a considerably larger number of monosubstituted benzenes existing in the form of pendant benzyl groups.
Fluorine‐containing polymers. III. Polymers and copolymers of 1,1‐dihydroperfluoroalkyl acrylates
Authors: Bovey F. A. , Abere J. F. , Rathmann G. B. , Sandberg C. L. 
Published: April 2003

AbstractThe preparation and properties of the homopolymers and butadiene copolymers of the 1,1‐dihydroperfluoroalkyl acrylates, CF3(CF2)nCH2OCOCHCH2. wherenhas been varied from 0 to 8, are described. Up through the hexyl member, the homopolymers are rubbers which can be vulcanized and which show outstanding resistance to solvents, particularly hydrocarbons. The octyl member can be obtained in either crystalline or rubbery form. The effect of side‐chain length on glass transition temperature and solubility is discussed. Incorporation of butadiene increases flexibility at low temperatures, although at some sacrifice of solvent resistance.
Fluorine‐containing polymers. VI. Copolymerization of 1,1‐dihydroperfluorobutyl acrylate
Authors: Sandberg C. L. , Bovey F. A. 
Published: April 2003

AbstractA study of the copolymerization of 1,1‐dihydroperfluorobutyl acrylate with methyl methacrylate, styrene, and butadiene has shown that this monomer is similar to acrylonitrile (e = 1.2, Q = 0.44) in its copolymerization behavior and considerably different from methyl acrylate (e = 0.6, Q = 0.42). This illustrates the strongly electronegative character of the C3F7 group. The higher Q value (0.75) may be considered evidence of higher resonance stability of the radical adduct due to the perfluoroalkyl substituent.
Viscosities of aqueous solutions of potassium cellulose sulfate in the presence of other electrolytes
Authors: Terayama Hiroshi 
Published: April 2003

AbstractViscosities of potassium cellulose sulfate solution were measured in the presence of KCl, HCl, BaCl2, and cetyl trimethyl ammonium bromide. The reduced viscosity of an aqueous solution of potassium cellulose sulfate was shown to follow the general formula proposed by Fuoss and Strauss for the polyelectrolyte solutions:

where A, B, and D are constants determined by experiments and c is concentration of the polyelectrolyte. In this article, a derivation of an empirical viscosity equation for the mixture of potassium cellulose sulfate and added electrolyte was shown. The empirical equation thus obtained for the mixture appears to express the viscosity behavior in the presence of low concentration of added electrolyte. The equation consists of two factors and has the following general form:

where A, B, D, a, b, ψ, and ϕ are all experimental constants. The first factor concerns the viscosity behavior of the aqueous solution of the polyelectrolyte in the absence of added electrolyte, and the second factor is the correction caused by the addition of electrolyte. The first factor increases while the second decreases upon dilution. As the results of the competitive tendencies, the existence of the maximum reduced viscosity at certain concentration of the polyelectrolyte can be explained. The physical picture corresponding to the first and the second factors respectively is not absolutely clear, but it is suggested that there exist two opposing tendencies that affect the viscometric behavior of a polyelectrolyte solution. One of these, that tends to increase the viscosity, is the increase in molecular dimensions upon dilution or upon decreasing the ionic strength. The second, that causes a decrease in viscosity, is attributable to the decrease in intermolecular interaction with dilution.
Polymerization of vinyl acetate at low temperatures
Authors: Burnett G. M. , George M. H. , Melville H. W. 
Published: April 2003

AbstractThe polymerization of vinyl acetate has been studied at temperatures down to −40°C. by means of a specially designed apparatus. The object of the experiments is to preparer polyvinyl acetates of as linear a character as possible by working at low temperatures in order to avoid transfer reaction to accumulating polymer. Polymers prepared at a number of temperatures have been examined osmotically and by the light‐scattering technique. Using the latter technique, it has been shown quite clearly that the size of the molecule, as measured by the dissymmetry measurements, gets smaller and smaller for a given molecular weight as the temperature of synthesis is decreased. It is believed that if the synthesis is carried out at temperatures below −30°C., then the molecules formed are predominantly linear in character.
Über die quantitative Berücksichtigung der Tyndall‐Absorption im UV‐Absorptionsspektrum von proteinen
Authors: Schauenstein E. , Bayzer H. 
Published: April 2003

AbstractAbsorptionsmessungen an Lösungen von reinstem γ‐Globulin, das einmal in nicht assoziiertem, ein zweites Mal in assoziiertem Zustand vorlag, liefern folgende Ergebnisse: (1) Die Tyndall‐Absorption gehorcht der Rayleigh‐Beziehung ε = K·v′n wobei sowohl ausserhalb, als auch innerhalb des Gebietes der Konsumptivabsorption die Grössen K und n innerhalb der normalen Fehlerbreite konstant bleiben. (2) Im Gebiet der Konsumptivabsorption darf Additivität zwischen konservativer und konsumptiver Lichtabsorption angenommen werden. Die mitgeteilten Ergebisse werden als Stütze für die Zulässigkeit der bisher angewendeten Korrekturmethode angesehen.
Kinetics of crystallization of some fractions of polyethylene succinate
Authors: Ueberreiter Kurt , Kanig Gerhard , Brenner Alexander S. 
Published: April 2003

AbstractPolyethylene succinate, prepared by condensation in solvents, has been fractionated into 6 fractions by repeated solvation and precipitation. Molecular weights of the fractions have been obtained by cryoscopic and titrimetric measurements. Dilatometric measurements at various temperatures gave the specific volumes of all fractions. The melting point (Tm)‐molecular weight relationship follows the function:

The velocity of crystallization of the polyester has been calculated from the change of volume with time during crystallization. It has a maximum at 30°C. for all chain lengths. The reciprocal half‐time of crystallization at the same temperature of crystallization decreases with increasing molecular weight of the polyester and finally approaches a limiting value.
Nucleation and growth of crystallites in high polymers. Formation of spherulites
Authors: Bryant W. M. D. , Pierce R. H. H. , Lindegren C. R. , Roberts R. 
Published: April 2003

AbstractEssential features of the crystallization of unoriented high polymers from the molten and supercooled liquid conditions are outlined to provide a background for a proposed structure and mechanism of growth of spherulites. Homogeneous and heterogeneous nucleation mechanisms of crystallite growth are discussed. Spherulites are recognized as crudely oriented spheroidal aggregates of crystallites and their attached amorphous regions. It is proposed that a spherulite originates from a single nucleus and that growth proceeds thence in a statistically radical fashion until all crystallizable domains are utilized or until growth is arrested due to increasing viscosity of the medium. It is assumed that crystallite growth occurs by lateral accretion of suitable oriented molecular segments and that nucleation proceeds from one crystallite to another by means of fine streamers of crystalline order (protofibrils) which may grow either by longitudinal extension along fringes or by lateral aggregation of very short segments. The predominant shapes of the crystallites are believed to determine the structure and optical properties of the spherulite. A roughly conical arrangement of crystallites around a spherulite radius is preferred to a helical one.
Calculation of molecular weight distribution functions from turbidimetric titrations and similar data
Authors: Claesson Stig 
Published: April 2003

AbstractA new method has been developed for obtaining molecular weight distribution curves from turbidimetric titration data. The latter are plotted directly in a curvilinear coordinate system where one set of axes is the solubility frequency curves for the polymer in question and which can be constructed once and for all. The method is very simple and no assumptions about the homogeneity of successive fractions are made. A formal mathematical treatment of the procedure is also given.
Nonlinear viscoelastic behavior of rubber in shear
Authors: Leaderman Herbert 
Published: April 2003

AbstractThe behavior in creep under constant load and recovery following removal of load is considered for certain nonlinear mechanical models. These models consist of a linear dashpot in parallel with a non‐Hookean spring for which the ratio deformation/stress increases with stress. Some data are presented on the nonlinear creep and recovery behavior in shear of raw and vulcanized rubbers. One of the models represents to a first approximation the deviations from linear viscoelastic behavior manifested by the rubber tested.
Acid‐base catalysis in polyelectrolyte solutions
Authors: Morawetz H. , Westhead E. W. 
Published: April 2003

AbstractThe rates of acid‐base catalyzed reactions of small molecules in polyelectrolyte solutions should, in general, differ from rates in simple electrolytes at the same pH. The effect is due to the small ionic activity coefficients and the counterion distribution in polyelectrolyte solution and will be accentuated if there is an energetic interaction between the polyion and the reacting molecules. In predicting the reactivity of groups attached to polyions, both electrostatic factors and specific chemical effects have to be considered. The reactivity of p‐nitrophenyl ester groups in neutral solution was observed to be increased by a factor of a million when groups were attached to a polymeric acid and the effect was interpreted by a change in the reaction mechanism. The rate of the basic hydrolysis of p‐nitroanilide groups attached to polymeric acids was very low and depended strongly on the substitution of both the α and the γ carbon. The pronounced acceleration of the hydrolysis by small concentrations of barium ions was interpreted as a chelation effect. The possible use of polyelectrolytes with reactive side chains as models of enzyme‐substrate complexes is discussed.
Ionic polymerization. VI. The mechanism of molecular termination by aromatic compounds in cationic polymerization of sytrene
Authors: Overberger C. G. , Endres Gerard F. 
Published: April 2003

AbstractEvidence is described concerning the mechanism of molecular termination by aromatic compounds in the cationic polymerization of syrene. Chemical analysis and infrared spectra of the polystyrenes produced by stannic chloride catalysis in the presence of thiophene, anisole, or p‐chloroanisole indicate that these compounds are incorporated into the polymer in the process of molecular termination, evidently as end groups. It is found that the molecular termination constant of p‐xylene is independent of the dielectric constant of the medium. Consideration of the relative values of the molecular termination constants of representative aromatic compounds reveals that their order of reactivity corresponds to the order of net electron‐donating character of the substituents attached to the aromatic nucleus. With the aid of the above facts, this leads to the conclusion that these compounds react with the carbonium ion‐anion pairs of the active centers by a mechanism analogous to that of the familiar Frindel Crafts alkylation. Since the three reactive aromatic hydrocarbons studied are found to have no detectable influence on the over‐all rate of polymerization, it is concluded that these compounds are chain transfer agents. p‐Chloroanisole accelerates the polymerization, while thiophene and, to a small extent, anisole, retard it. The broader applicability of the molecular termination equation to cationic than to free radical polymerization is disscussed, and some suggestions are made concerning the mechanism of spontaneous termination and chain transfer with the monomer in the cationic polymerization of styrene.