bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheology of polyisobutylene. II. Low molecular weight polymers
Authors: Leaderman Herbert , Smith Robert G. , Jones Robert W.
Published: April 2003

The flow and retarded‐elastic behavior of four polyisobutylene specimens (M̄w 1.09 × 104 to 8.54 × 104), measured in a concentric cylinder rotational viscometer, are reported. Under the conditions investigated the non‐Newtonian flow behavior can be represented by Ferry's equation. The logarithm of the viscosity η varied linearly with the reciprocal of the square of the absolute temperature. The time‐scale for retarded elasticity was found to vary with temperature in the same way as the viscosity. The normalized retarded elasticity functions at temperatures corresponding to unit viscosity are substantially identical. The time corresponding to a normalized retarded elastic compliance of 0.5 is about 10−5 η second when η is in poises. The reciprocal steady state shear compliances 1/J and internal shear moduli Gi in Ferry's equation are of the same order of magnitude for each polymer. The retardation time function L(ln τ) is calculated for one of the polymers, and then the dynamic response; these results are in good agreement with dynamic measurements on this material. From a consideration of the stress relaxation behavior of high molecular polymers, it is pointed out that there must exist another retarded elasticity mechanism, the time‐scale of which depends only on temperature and not on molecular weight. This second mechanism is masked in the reported experiments on low molecular polymers.
The concentration dependence of the sedimentation constants of flexible macromolecules
Authors: Wales M. , Van Holde K. E.
Published: April 2003

Data for a number of vinyl polymer‐solvent systems show that the constant Ks in the relation 1/S = (1/S0) (1 + KsC) (where S and S0 are sedimentation constants at the concentration C and zero respectively) is proportional to the intrinsic viscosity. The average constant of proportionality is 1.6. Assuming the Mandelkern‐Flory theory of the relation of frictional coefficient and intrinsic viscosity to root‐mean‐square end‐to‐end distance and Burgers' relation for the sedimentation constant of a dilute suspension of spheres, the ratio Ks/[η] is calculated to be 1.66. Molecular weights may be calculated from Ks and the limiting sedimentation constant, S0 without the use of the constants Φ and P, and agree well with molecular weights determined independently. These considerations apparently do not apply to cellulose derivatives, for which Ks is not proportional to [η].
Reactivity of polar monomers in copolymerization
Authors: Ham George E.
Published: April 2003

As a consequence of earlier establishment of electrostatic repulsion between nonterminal polar 1,2‐disubstituted olefins in polymers and like adding monomer, polar methylenic monomers were examined for such an effect. Acrylonitrile was found to exhibit such behavior in at least three systems: styrene–acrylonitrile, α‐methylstyrene–acrylonitrile, and α‐acetoxystyrene–acrylonitrile. Absence of such an effect was shown for methacrylonitrile, methyl acrylate, acrylic acid, methacrylic acid, and crotonic acid. A modified copolymerization equation involving r1, r, and r2 was presented. A convenient means of estimating r1 and r2 in this equation as well as in the ordinary copolymerization equation was shown.
Some properties of polyacetaldehyde rubber
Authors: Bovey F. A. , Wands R. C.
Published: April 2003

Certain physical and chemical properties of samples of polyacetaldehyde prepared by M. Letort have been examined. Study of the rheological behavior of high molecular weight specimens of this polymer indicates that its internal strength is high, and that it shows typical rubbery elasticity. Under rapidly applied stresses, it shows a high modulus, indicating a high degree of internal friction. Correlated with this is a relatively high brittle point. Upon pyrolysis the polymer depolymerizes to yield the monomer, and likewise undergoes chain cleavage. About 200–400 monomer units are lost for each cleavage of the chain.
Viscosity of 25% solutions of cellulose acetate versus intrinsic viscosity distribution
Authors: Rosenthal A. J. , White B. B.
Published: April 2003

The 25% w/w solutions of blends of cellulose acetate fractions have higher viscosities than solutions of single fractions of the same average intrinsic viscosity. It was found that the viscosity of a blend can be related to its composition by the relationship:

where \documentclass{article}\pagestyle{empty}\begin{document}$[\bar \eta ]_{25\%}$\end{document} is the apparent intrinsic viscosity of the cellulose acetate blend in solution at 25% concentration, and [η]i are the intrinsic viscosities of the components. By application of this equation it was determined that only a portion of the high anomalous viscosity of solutions of cellulose acetate prepared from viscose grade wood pulp could be attributed to intrinsic viscosity distribution.
Relaxation distribution functions of polyisobutylenes in concentrated solutions
Authors: Ferry John D. , Jordan Ivo , Evans Warren W. , Johnson Myrle F.
Published: April 2003

Relaxation distribution functions for concentrated solutions of six polyisobutylene samples, using three different solvents, have been derived from measurements by the methods of the single transducer, wave propagation, and stress relaxation following cessation of steady‐state flow. The ranges of molecular weight, concentration, and temperature were about 0.3 to 2.5 × 106, 5 to 40%, and −5 to 40°C., respectively. When plotted with reduced variables with a reference state of unit density and viscosity at a standard temperature, data at different temperatures superpose; data at different concentrations superpose except for the two samples of highest molecular weight, where there are perceptible deviations. The reduced distribution functions for all the samples lie close together at long times where there is a drop associated with the finite lengths of the molecules. The theory of Rouse for viscoelastic properties of dilute solutions, when modified for concentrated solutions by assuming that all segmental mobilities are equally affected by interlacing of neighboring molecules, agrees with the reduced mechanical properties at long times fairly well. However, it does not predict the plateau region characteristic of distribution functions of polymers of high molecular weight. The existence of this plateau in concentrated solutions and undiluted polymers represents an abnormal prolongation of the longest relaxation times in these systems, which is attributed to molecular coupling by entanglement as discussed by Bueche with respect to steady flow viscosity.
The dielectric increment of a carboxymethylcellulose as a function of the degree of ionization
Authors: Allgén Lars‐Göran
Published: April 2003

The dielectric increment of a specimen of carboxymethylcellulose in aqueous solution has been studied as a function of pH. For the free acid a low increment was obtained which increased with increasing ionization (sodium salt). With excess sodium or hydrogen ions the increment decreased. Similarly there was a marked increase of the increment per gram per liter for the sodium salt with increasing dilution. The dielectic increments obtained for various salts of carboxymethylcellulose followed the order: Li+ > Na+ > NH4+ > K+ in agreement with the ion exchange affinities found previously for these ions (reversed order). The data have been interpreted along the lines of current theories for polyelectrolytes, by taking into consideration the net charge of the polyion, and the polyion‐counterion association under varying conditions.
Water induced acceleration of the diffusion of organic vapors in polymers
Authors: Long F. A. , Thompson L. J.
Published: April 2003

The influence of water vapor on the rate of diffusion of organic molecules has been studied at 40°C. by the sorption method for the systems water‐acetone‐polyvinyl acetate, water‐carbon tetrachloride‐polyvinyl acetate, water‐acetone‐cellulose acetate (37.9% acetyl) and water‐benzene‐polystyrene. For the first three systems the rate of diffusion of the organic vapor is markedly faster for the mixture of water and organic vapor than for the pure organic vapor. With polyvinyl acetate, the rate of diffusion of 80 mm. of acetone is increased about 25‐fold if 36 mm. of water vapor is mixed with the acetone. Diffusion of the larger carbon tetrachloride molecule is accelerated by water even more than is acetone. Water vapor at a pressure of 36 mm. causes about a 30‐fold increase in the rate of diffusion of 80 mm. of acetone into cellulose acetate even though the diffusion of acetone itself into cellulose acetate is anomalous. With polystyrene the presence of water vapor causes no acceleration of the diffusion of benzene which is the expected result since, in contrast to the other two polymers, polystyrene sorbs only very small amounts of water. It is concluded that the marked effect of water vapor on the diffusion of organic vapors into polyvinyl acetate and cellulose acetate involves (a) a rapid diffusion of water into the polymer and (b) more rapid diffusion of the organic vapor into the “water plasticized” polymer than into the dry polymer.
Polyelectrolytes. XI. Electrophoresis in solutions of poly‐4‐vinyl‐N‐n‐butylpyridinium bromide
Authors: FitzGerald Emerson B. , Fuoss Raymond M.
Published: April 2003

The following systems were observed in the Tiselius moving boundary apparatus: (1) poly‐4‐vinyl‐N‐n‐butylpyridinium bromide (PBr) with added potassium bromide/potassium bromide in osmotic equilibrium with the PBr‐KBr solution; (2) KBr/PBr, both solutions adjusted initially to the same conductance; (3) LiBr/PBr and (4) PBr‐(c1)/PBr(c2). Series 1 showed that the mobility of the polycation decreased with increasing KBr concentration. The schlieren patterns were strikingly asymmetric. Series 2 showed that the mobility of the polycation does not depend very much on molecular weight. Series 3 showed strong interaction between polyelectrolyte and simple electrolyte. Series 4 indicates that the mobility of the polycation depends on concentration much more than in the case of simple electrolytes. Both in Series 3 and 4, more moving boundaries appeared than are theoretically called for by the number of ionic species present.
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

Styrene 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.
Chain transfer in solution polymerization. II. Vinyl acetate
Authors: Kapur S. L. , Joshi R. M.
Published: April 2003

A study of chain transfer in the peroxide catalyzed polymerization of vinyl acetate in the presence of fourteen solvents has been made and chain transfer constants calculated. The dependence of chain transfer activity on the structure is discussed.
Effect of molecular weight distribution on gel formation by high energy radiation
Authors: Charlesby A.
Published: April 2003

The 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

Reaction 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

Polyhydrocarbons 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

Hydrocarbon 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

Equilibrium 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

An 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

Recently 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

Methyl 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

Studies 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

The 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

The 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

A 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

Viscosities 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

The 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

Absorptionsmessungen 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

Polyethylene 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

Essential 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

A 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

The 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

The 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

Evidence 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.
Kinetic constants for styrene polymerization
Authors: Tobolsky A. V. , Offenbach J.
Published: April 2003

Values for A′ and Ctr,m for styrene polymerization between 0 and 90° are presented. These are important for accurate calculation of rates of initiation.
Complex formation and reversibility in copolymerization
Authors: Walling Cheves
Published: April 2003

Barb's data4–6 on the copolymerization of styrene and sulfur dioxide are reviewed and shown to be in agreement with a scheme in which styrene‐sulfur dioxide complexes are not involved, but in which attack of a growing chain on sulfur dioxide is a rapidly reversible process at all temperatures, while, at higher temperatures, addition of a chain ending in sulfur dioxide to styrene becomes reversible as well. Eact for the loss of SO2 is estimated as lying between 4 and 14 kcal., while a chain ending in a sequence of styrene units reacts with SO2 at least 100 times as readily as with styrene. A similar interpretation is made of the ethylene‐carbon monoxide copolymerization,14 in which addition of CO appears to be a reversible process, since the amount of CO in the polymer increases with total pressure. Some other systems in which reversibility of chain propagation might be expected to affect copolymer compositions are pointed out.
Molecular configuration of gelatin
Authors: Gouinlock E. V. , Flory P. J. , Scheraga H. A.
Published: April 2003

Intrinsic viscosities, light scattering turbidities and dissymmetries, and sedimentation constants have been determined for each of two high molecular weight gelatin fractions in 1 M KCNS, pH 6.5, at 30°. Their weight‐average molecular weights and z‐average radii of gyration were 6.0 × 105 and 280 A., and 3.8 × 105 and 240 A., respectively. The ratio [η]M/(r2)3/2, after allowance for the influence of molecular weight heterogeneity, approximates the accepted value of the viscosity parameter Φ. The values of \documentclass{article}\pagestyle{empty}\begin{document}$ {{M(1 - \bar \upsilon \rho )} \mathord{\left/ {\vphantom {{M(1 - \bar \upsilon \rho )} {NS_{0\eta 0} }}} \right. \kern-\nulldelimiterspace} {NS_{0\eta 0} }}(\overline {r^2 } )^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} very nearly agree with the normal value of the parameter P for the frictional coefficient when the experimental errors, molecular weight heterogeneity, and a possible small amount of selective binding of KCNS are taken into account. Similarly, the ratio \documentclass{article}\pagestyle{empty}\begin{document}$ {{NS_0 [\eta ]^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} \eta _0 } \mathord{\left/ {\vphantom {{NS_0 [\eta ]^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} \eta _0 } {M^{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} }}} \right. \kern-\nulldelimiterspace} {M^{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} }}(1 - \bar \upsilon \rho ) $\end{document} is almost equal to, though somewhat lower than, the normal value of Φ1/3P−1 if the same factors are taken into account. The molecular dimension ratio \documentclass{article}\pagestyle{empty}\begin{document}$ ({{\overline {r_0^2 } } \mathord{\left/ {\vphantom {{\overline {r_0^2 } } M}} \right. \kern-\nulldelimiterspace} M})^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} $\end{document} computed for the unperturbed gelatin molecule is indistinguisahble from that for various synthetic polymers. The ratio of \documentclass{article}\pagestyle{empty}\begin{document}$ (\overline {r_0^2 } )^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} $\end{document} to the value calculated assuming free rotation is 1.8 to 1.9, which indicates a degree of chain flexibility similar to that occuring in synthetic polymers. We conclude that the configurational character of the gelatin chain in aqueous media is not much affected by its polar linkages or by intramolecular hydrogen bonding.
Precision viscometry of polymer solutions
Authors: Kooy J. , Hermans J. J.
Published: April 2003

The article describes a method for measuring times of efflux in a capillary viscometer with an accuracy of 0.003 sec. A film is taken of the moving meniscus together with a synchronous clock. The temperature of the thermostat bath is controlled to within 0.001°C. by means of a Wheatstone bridge which contains temperature dependent resistances. Experimental results obtained with a polystyrene sample in toluene show no systematic deviation from linearity in the ηsp/c vs. c curve between 2 × 10−3 and 3 × 10−5 g./ml. The same curve for a sample of polymethacrylate in water shows a sharp maximum at about 10−4 g./ml.
A direct analytical test of the Flory‐Schulz distribution in nylon 6 type equilibrium polymers. Preliminary communication
Authors: Hermans P. H. , Heikens D. , Van Velden P. F.
Published: April 2003

The validity of the Flory‐Schulz distribution of chain length in equilibrium polymers produced from ϵ‐caprolactam and water (Nylon 6) over a DP range from ∼14 to ∼90 is tested by determination of the content of monomer (ϵ‐aminocaproic acid, ACA) by means of a chromatographic technique. Experiments show general agreement with a simple theoretical relationship (P̄n1 = N, where P̄ = number average DP of chains, n1 = number of ACA molecules, and N = total number of chains), required for equilibrium if equal reactivity of all functional groups independent of chain length is assumed. Moderate deveiations from this relation, which seem to occur at higher DP values (P̄ ∼ 90) require further investigation.
Polyphenyl
Authors: Edwards Gerald A. , Goldfinger George
Published: April 2003

A substance indentified as polyphenyl1,2 has been obtained by the condensation of paradichlorobenzene using the Wurtz‐Fittig reaction. The viscosity behavior of polyphenyl is unusual. The curves obtained by plotting specific viscosity divided by concentration versus concentration pass through a maximum at very low concentrations, reaching a constant value at a concentration of about one percent. In the region of the maximum, the specific viscosity divided by the concentration is dependent on the rate of shear, increasing with decreasing rate of shear.
The preparation and characterization of block copolymers
Authors: Woodward A. E. , Smets G.
Published: April 2003

Block copolymers have been synthesized by heating a polymer, containing peroxidic linkages, in the presence of another monomer. The peroxide groups were introduced into the first polymer by initiating the controlled polymerization of its monomer with phthalyl peroxide. Separation of the block copolymers from the two parent homopolymers was made possible by their different solubilities in selected solvents or their mixtures. Polystyrene (Mn = 1.00 × 105), prepared at 75°C. in bulk with 0.5% phthalyl peroxide, initiated the polymerization of methyl methacrylate at 100°C. in benzene solution. The two block copolymer components isolated were found by infrared analysis to contain 22 and 30% polystyrene with number average molecular weights of 4.3×105 and 3.0×105, respectively. Block copolymers were also obtained by heating styrene in benzene at 85°C. with polyvinyl acetate (Mn = 0.60 × 105), prepared in benzene solution at 70°C. with 0.5% peroxide. A 39% vinyl acetate‐61% styrene block copolymer was isolated and found to have a molecular weight of 1.65×105. Intrinsic viscosities, μ values, and κ′ values for the block copolymers and related homopolymers were determined and are discussed in terms of composition, molecular weight, and poly‐dispersity. Other experiments indicated that styrene‐phthalyl peroxide polymers were unable to initiate vinyl acetate or vinylpyrrolidone polymerizations at 100°C. in significant amounts; this behavior is interpreted in terms of the stability of the radicals formed.
Molecular weight of polyvinyl acetate by light scattering and viscosity techniques
Authors: Chinai S. N. , Scherer P. C. , Levi D. W.
Published: April 2003

A viscosity‐weight average molecular weight relationship was obtained for fractionated polyvinyl acetate in a thermodynamically “good” solvent acetone at 30°C. This relationship is represented by [η] = 8.6 × 10−5M. The value of the root‐meansquare end‐to‐end distance is approximately three times as large as the theoretical value for a chain with completely free rotation. The values of the osmotic second virial coefficient indicate the polymer molecules are expanded beyond their random flight dimensions. Consideration of the thermodynamic interactions in “good” solvent results in approximately constant values for A2M/[η] and A2M2/(r2)3/2. The average value obtained for the Flory universal constant is 1.98 × 1021.
Acrylonitrile polymerization in homogeneous solution
Authors: Thomas W. M. , Gleason E. H. , Pellon J. J.
Published: April 2003

Previous kinetic studies of acrylonitrile polymerization in bulk disclosed unexpected features that were associated with the heterogeneous nature of the system. In the present work, polymerization was carried out in homogeneous solution, principally in dimethyl formamide. Polymerization rate in dimethylformamide was dependent on the square root of the azo initiator concentration and approximately on the three‐halves power of the monomer concentration. Over‐all activation energy was 21 kcal./mole. Rates were slow in this solvent and molecular weights were low. Chain transfer activity of several liquids was estimated by substituting them for part of the dimethylformamide. Contrast between results in the homogeneous and heterogeneous cases is explained as due to removal by solvent of any opportunity for radical burial or catalyst enrichment. Standard kinetic treatments do not explain quite adequately the details of rate and molecular weight dependence on monomer. It appears that sluggish radicals are formed by chain transfer to solvent. A kinetic scheme is proposed to account for these observations.
Bis‐type modifiers in polymerization. II. Comparison of effectiveness of various compounds in emulsion butadiene and bulk styrene polymerizations
Authors: Costanza A. J. , Coleman R. J. , Pierson R. M. , Marvel C. S. , King Charles
Published: April 2003

The present paper describes the preparation and evaluation of the effectiveness as modifiers of a number of compounds of bis‐type structure—principally aryl disulfides—in bulk styrene and emulsion butadiene polymerizations. This work endeavors to explore some of the objectives described in the first paper of this series, and deals primarily with attempts to gain quantitative information on the effect of the nature and location of substituting groups with respect to the dissociating bond. The compounds examined include both those containing reactive groups attached and those lacking such groups. A number of the preparations are now compounds. Evaluations in 50°C. bulk styrene were carried out with the objective of eliminating the complications of the diffusion factor always present in emulsion systems. Generally speaking, the correlation between effectiveness in bulk styrene and 50°C. emulsion butadiene was quite good, though there were exceptions. It was found that the modifier activity of many compounds in emulsion butadiene could be enhanced by predispersing them in the aqueous phase—presumably a result of minimizing the importance of diffusion rate. Some of the modifiers were also tested in a low temperature butadiene emulsion system. Aryl disulfides continue to offer the most promise from the standpoint of combining the features of attaining high transfer constants and ease of incorporating desired reactive groups. Some compounds had adequate activity in emulsion butadiene polymerizations for use as practical modifiers. However, it has not yet been established that these compounds cleave to give one‐half the molecule on each end of the butadiene polymer chain, as has been done for styrene polymers.
Activity of counter ion in polyelectrolyte solutions
Authors: Kagawa Ikumi , Katsuura Kakuji
Published: April 2003

The activity of silver ion was measured potentiometrically with various sample solutions of silver or silver‐sodium salt, prepared from three different kinds of carboxymethylcellulose, for the purpose of elucidating these several points: dependence of the activity coefficient of counter ion upon the concentration of polyelectrolyte in salt‐free solutions; influence of the silver content of the sample upon activity coefficient; salt effect on activity coefficient; and dependence of activity coefficient upon the degree of neutralization. These experimental results indicate that the characteristics of polyelectrolyte solutions are in many respects quite different from those of simple electrolyte solutions. The applicability of the theory proposed by Ōsawa, Imai, and Kagawa is discussed in some detail, although the discussion is restricted to the salt‐free system only.
Viscosity measurements in branched silicones
Authors: Charlesby A.
Published: April 2003

Exposure to high energy radiation offers a means of producing controlled branching in long chain polymers. Branched silicone polymer molecules were obtained by exposing linear molecules to high energy radiation. The increase in weight‐average molecular weight calculated theoretically from the radiation dose was compared with the value deduced from measurements of intrinsic and bulk viscosity, ignoring the effect of branching. The ratio of these measurements show the apparent reduction in molecular weight (as measured by viscosity methods) when branched molecules are present. In particular it is found that the reciprocal bulk viscosity decreases uniformly with degree of branching (or crosslinking) until the gel point, when the weight‐average and bulk viscosity become infinite.
An intrinsic viscosity‐molecular weight relation for polyacrylonitrile
Authors: Cleland Robert L. , Stockmayer Walter H.
Published: April 2003

Weight‐average molecular weights and intrinsic viscosities in dimethyl formamide at 25° have been measured for four unfractionated low‐conversion acrylonitrile polymers covering the molecular weight range 30 to 250 thousand. The results follow the equation: