bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on biocolloids and polyelectrolytes—the plant—gums viscosity of azrechtic acid
Authors: Kulshrestha V. K.
Published: April 2003

Azrechtic acid (ARA) has been obtained by the electrodialysis of an aqueous solution of the gum of Azadirechta indica in an acidic medium. The viscosity of this gum acid has been investigated under different experimental conditions, i.e., with dilution in aqueous and in isoionic concentration of added electrolyte (HCl), and with change in pH. It is observed that the reduced viscosity of the aqueous solutions increases rapidly with dilution and the reduced viscosity—concentration curve is concave upwards instead of being linear as in the case of linear polymers. The viscosity of aqueous ARS solutions follows the equation, ηsp/C = A/(1 + B√C) where A, B, and D are constants (A = 0.03, B = 0.1845, and D = 0.05), as well as the equation ηsp/C = aCb, in which a and b are constants and equal to 0.2113 and −0.4375, respectively. It is observed that in isoionic concentrations of added electrolyte (HCl, 2.20 × 10−4 g.‐equiv./l.), the sharp rise in the ηsp/C versus C curve vanishes, and the curves show well defined maxima which shift to higher concentrations of the gum acid as the electrolyte concentration increases and ultimately vanish at sufficiently high concentration of the added electrolyte (HCl, 2.20 × 10−3 g.‐equiv./l.), and the ηsp/C versus C curves become linear. The viscosity of azrechtic acid at constant solute concentration increases rapidly when the pH is increased by the addition of NaOH, becomes maximum at a pH of about 6, after which it falls rapidly and becomes constant after a pH of 12. The viscosity also decreases when the pH is decreased on addition of HCl and becomes constant after a pH of 2.0. All these phenomena have been explained on the basis that azrechtic acid behaves as a polyelectrolyte.
Differential thermal analysis of high polymers. VI. Comments on some material and experimental factors
Authors: Ke Bacon
Published: April 2003

Some factors in the differential thermal analysis (DTA) of high polymers were studied. A newly designed, small cell assembly was used in most of the work. The thermal history and, to a lesser extent, the molecular weight affect the size and shape of the thermogram, depending on the amount of crystallinity and the distribution of crystallite sizes in the polymer. Interference due to oxidation should be prevented in the characterization of a thermally unstable polymer. Large sample quantity may lead to multiple peaks in the thermogram. High heating rates result in more intense peaks but also shift peak positions. Thermogram profiles become distorted when the temperaturesensing thermocouple is placed in the sample.
Preparation and properties of copolymers of maleic anhydride and 2,2‐dimethylaminoethyl methacrylate
Authors: Taylor W. D. , Woodward A. E.
Published: April 2003

Preparation of copolymers by reaction of N,N‐dimethylaminoethyl methacrylate with maleic anhydride in an excess of the latter and the presence of water is described. The reaction products have been characterized by elemental analysis, by conductiometric titrations with acid and with base, and by specific viscosity determinations and light‐scattering measurements in dilute solution. Although there is evidence that a 1:1 copolymer is formed, the results of the titrations and viscosity measurements indicate that this reaction product is a polyacid and not a polyampholyte. Light‐scattering measurements indicate that aggregation occurs in aqueous solutions of this polymer. Attempts to prepare regularly alternating polyampholytes from other monomer combinations are described.
Polymers derived from unsaturated esters of hydronopoxyalkanols
Authors: Shono Toshiyuki , Marvel C. S.
Published: April 2003

Homopolymers of the acrylates of a series of hydronopoxyalkanols have been prepared and characterized as soft rubbery materials with some adhesive properties. The polymer from the methacrylate of hydronopoxyethanol was hard, brittle and insoluble. The crotonate of this alcohol did not homopolymerize was hard, brittle and insoluble. The crotonate of this alcohol did not homopolymerize in a free radical system. All of these esters copolymerized readily with vinyl chloride, styrene, acrylonitrile and butadiene. The vinyl chloride copolymers and styrene copolymers were rigid plastics. The butadiene copolymers were rubbery and easily crosslinked in air. The acrylonitrile copolymers were soluble in dimethylformamide. Terpolymers of these esters with butadiene and acrylonitrile were tough, rubbery compositions.
Steric structures in copolymerization
Authors: Berger M.
Published: April 2003

Using normal copolymerization equations we have developed graphical techniques for predicting the amount of crystallinity in ethylene–propylene copolymers.
Polymerization and copolymerization of 1‐ and 9‐vinylanthracenes and 9‐vinylphenanthrene
Authors: Katz Dov
Published: April 2003

The free radical polymerization and copolymerization with styrene of 1‐ and 9‐vinylanthracenes and 9‐vinylphenanthrene was studied. The highest reactivity was shown by 9‐vinylphenanthrene and the lowest by 9‐vinylanthracene. From the experimental data on the copolymerization reactions the reactivity ratios r1 and r2 were calculated and for the two vinylanthracenes the values of Q2 (general reactivity) were obtained after application of the Price‐Alfrey scheme for correlating reactivities of vinyl compounds in copolymerization. The scheme was not used for 9‐vinylphenanthrene as the product of r1 × r2 was in this case greater than unity. It appears that the rates of polymerization (and copolymerization) of the three monomers are influenced by two factors: the steric hindrance to conjugation between the anthracene or phenanthrene system and the exocyclic double bond, and the nonaromatic character of the 9,10 double bond in phenanthrene. In 9‐vinylanthracene the conjugation between the anthracene system and the vinyl group is sterically more hindered that in the 1‐isomer, the resonance stabilization of the radical adduct of 1‐vinylanthracene is greater than in the case of the 9‐isomer and the latter is less reactive. In 9‐vinylphenanthrene and 1‐vinylanthracene the steric hindrance is the same and the higher reactivity of the first monomer as compared with the second seems to be due to the non‐aromatic character of the 9, 10 double bond in phenanthrene, which makes the 9‐vinylphenanthrene and almost aliphatic diene.
Transient analysis of a vibrating reed
Authors: Glauz R. D.
Published: April 2003

A new simplified test for obtaining the physical properties of a viscoelastic material is described and analyzed. A reed, clamped at one end, is displaced at the free end and the damped oscillations measured. From measurements of the damping factor and frequency the complex modulus is computed. Tables of eigenvalues have been calculated for various masses and moments of inertia attached to the free end of the reed. Many experimental tests have shown the simplicity and usefulness of the method.
Self‐diffusion and nuclear relaxation in polyisobutylene
Authors: McCall David W. , Douglass Dean C. , Anderson Ernest W.
Published: April 2003

Various self‐diffusion and nuclear relaxation experiments are reported for a polyisobutylene of rather low molecular weight, in bulk and in solution. In the bulk, the self‐diffusion coefficient obeys the Arrhenius relation, yielding an activation energy of 5.5 kcal./mole. In solution the activation energies are lower, approaching the value for the solvent at low concentration. The self‐diffusion coefficient of the polymer at infinite dilution is 1.2 × 10−5 cm.2/sec. in CS2 and 0.44 × 10−5 cm.2/sec. in CCl4. The ratio is close to the inverse ratio of the solvent viscosities. Measurements of self‐diffusion of the solvent have been made for cyclohexane in polyisobutylene. A simple interpretation of the data in terms of Stokes‐Einstein models yields molecular dimensions which are too small by a factor of two or three.
Narrow molecular weight distribution polystyrenes
Authors: Brower F. M. , McCormick H. W.
Published: April 2003

A study of the scope and limitations of the anionic polymerization of styrene and substituted styrenes under conditions in which a chain termination reaction is lacking was made. Under these conditions polymers of very narrow molecular weight distributions were obtained. Ultracentrifuge data are presented as evidence confirming the formation of narrow distributions. All reagents used were carefully purified and subsequently were not exposed to the atmosphere. Standard procedure was to conduct the polymerizations by adding monomer solution slowly to initiator solution. Deviations from this procedure were designed to study various reaction conditions. Monomers used were styrene, α‐methylstyrene, and m‐ and p‐vinyltoluene. Solvents used were tetrahydrofuran, tetrahydropyran, 2‐methyl‐tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether. Initiators used were sodium–naphthalene, sodium–biphenyl, sodium–α‐methylstyrene, sodium–phenanthrene, and lithium–naphthalene. The choice of solvent had a great effect on the course of the polymerization and the temperature at which narrow distribution polymers could be produced. Solvents promoting rapid initiation and relatively slow propagation were best, and those promoting the reverse situation tended to give side reactions leading to termination and abroad distribution polymer. The order of promotion of rapid initiation and slow propagation for these solvents is dioxan > tetrahydrofuran > ethylene glycol dimethyl ether > diethylene glycol dimethyl ether. In dioxane solutions monodisperse polymer was prepared under a wide range of conditions. Monodisperse polymer could not be prepared under the most favorable conditions in diethylene glycol dimethyl ether. These effects were interpreted in terms of ion pair separation. Other factors which might lead to broad distribution polymers were examined. The age of the initiator was found to be very important, order initiator solutions giving broad distribution polymers. Aged initiator solutions were found to evolve hydrogen when allowed to react with water; freshly prepared initiator solutions evolved on hydrogen. In the presence of toluene there was chain transfer to the methyl group giving a broad distribution polymer. Similar transfer to benzene at the ring gave termination before polymerization was complete. Rusty iron, Fe2O3, and Fe3O4 adversely effected the course of polymerizations giving broad distribution polymers. Hydrogen‐reduced iron in the reaction mixture resulted in only minor deviation from narrow distribution.
Effect of solvents on the anionic polymerization of styrene by phenyllithium
Authors: Zilkha Albert , Barzakay Samuel , Ottolenghi Ariel
Published: April 2003

The anionic polymerization of styrene by phenyllithium was studied in various solvents The order of the decreasing molecular weights obtained depending on the solvent, was: tetrahydrofuran » toluene > benzene > petroleum ether > diethyl ether. The molecular weight, due to absence of termination, is governed by the ratio of the rate propagation to the rate of initiation (Rp/Ri). Both these rates are influenced by the dielectric constant and the solvating power of the solvent for the phenyllithium and for the growing end, solvation of the growing end being greater due to the resonance of the propagating styryl anions. This leads to the fact that on passing from petroleum ether (low dielectric constant) to tetrahydrofuran (relatively high dielectric constant and high solvating power), Rp increases much more than Ri, leading to higher molecular weight. The polymerization of styrene in mixtures of petroleum ether and tetrahydrofuran was studied by the addition of increasing amounts of tetrahydrofuran while keeping the catalyst and monomer concentrations constant. Initially (up to 2 vol.‐% tetrahydrofuran) there was a sharp decrease in molecular weight due to a greater dissociation of the phenyllithium, with a corresponding increase in Ri. On further addition of tetrahydrofuran (up to about 25 vol.‐%), the molecular weight increased and approached the order of that obtained in petroleum ether. This is due to a greater increase in Rp over Ri due to greater solvation of the propagating end. At this relatively high tetrahydrofuran concentration we have maximum solvation both of the catalyst and of the growing end. With further addition of tetrahydrofuran there is a linear dependence of the molecular weight both on the concentration of the tetrahydrofuran and on the dielectric constant of the system. Ether gave the lowest molecular weights, in spite of its relatively high dielectric constant, due to greater dissociation of the catalyst associates (C6H5Li)x leading to an increased efficiency of the catalyst (greater Ri). Toluene and benzene led to higher molecular weights than petroleum ether, although the dielectric constants are of approximately the same order, due to the homogeneous nature of the polymerization in these solvents as compared with the heterogeneous polymerization in petroleum ether. The molecular weight increased with decrease in temperature in various solvents due to the increase in the dielectric constant and the lowering in Ri
The reference point for liquid relaxation processes. II. Melt viscosity of polyisobutylene
Authors: Miller A. A.
Published: April 2003

Published (Fox and Flory) viscosity—temperature data for polyisobutylene are expressed by a modified Arrhenius equation: log η = log A + B′/(T ‐ T0). For higher molecular weight fractions (M > 2000) with estimated glass temperatures in the range Tg = −64 to −79°C., the derived reference temperature T0 is −150 (±10)°C., and B′ = 1240°. By comparison with Fox and Flory's empirical equations, the molecular weight dependency of the A parameter, below and above the “chain‐entanglement” point (M = 17000), is derived. The modified Arrhenius equation can also be expressed with WLF (Williams‐Landel‐Ferry) constants, where T0 = Tg − C and B′ = CC. The melt viscosity—temperature behavior is consistent with free−volume concepts if vf ⋍ (T − T0), as suggested by the Cohen‐Turnbull theory.
Morphology of polyethylene single crystals
Authors: Giordano Orsini P. , Marchese B. , Mazzarella L.
Published: April 2003

An electron microscope study of polyethylene single crystals is reported. The following points have been investigated: (1) influence of crystallization temperature on crystal shape; (2) effect of solvent etching on already formed crystals. Crystals were deposited from very dilute solutions at temperature ranging between 80 and 120°C. Solvents like xylene, butyl acetate, isoamyl acetate, and diphenyl ether were used. Besides the already reported true and truncated lozenges, hexagonal crystals have been obtained with tendency to regularity as the temperature of crystallization increases. The melting point of hexagonal crystals is somewhat lower than that of lozenges. Their structure, as revealed by electron diffraction, is orthorhombic, similar to that of lozenges. Diamond‐shaped crystals etched with solvent under strictly controlled conditions display unexpected morphology. The peripheral region of the crystal of the sectors composing the crystals is characterized by a lower solubility and a lower density.
Solid state polymerization of methacrylamide and N‐arylmethacrylamides
Authors: Jäuger P. , Waight E. S.
Published: April 2003

The γ‐ray initiated solid state polymerization of methacrylamide at room temperature has been described and discussed in terms of reaction mechanisms previously applied to the radiation‐induced polymerization of acrylamide. Log (M0/M) increased, after a short initiation period, linearly with (time)2 up to conversions of about 20%. This was followed at higher conversions by a second linear region with a higher slope. The conversion rate (%/Mrad.) increased for intensities between 0.3 and 0.075 Mrad./hr., but it dropped unexpectedly at the lowest dose rates. Irradiated methacrylamide showed a post‐irradiation polymerization, the rate of which was influenced by the presence of air for reaction times longer than 200 hr. Among the solid N‐arylmethacrylamides, which were all less reactive than methacrylamide, some ortho‐substituted compounds (o‐Cl, o‐Br, o‐ethoxy) showed a relatively high reactivity. These results are discussed in connection with differences in hydrogen bonding found in the infrared spectra.
Specific diluent effects on polymer chain dimensions
Authors: Hoeve C. A. J. , O'Brien M. K.
Published: April 2003

Specific diluent effects on the unperturbed mean‐square end‐to‐end distance < r02 > may be determined in dilute solutions at their Θ‐points. Another method to determine these effects is described in this paper. It involves the measurement of the modulus of crosslinked polymers swollen with different diluents and interpretation of the results according to current rubber elasticity theory. As a result of the relatively high concentrations used in this method, combined with the introduction of crosslinks, specific diluent effects on chain dimensions are obtained, unobscured by excluded volume effects. The method is applied to polyethylene diluted with di‐2‐ethylhexyl azelate, α‐chloronaphthalene, n‐paraffin, tetralin, and n‐hexadecane. Within 10% the value of < r02 > in n‐hexadecane is equal to that in the other diluents used. In view of the similarity of the polyethylene molecule to those of n‐hexadecane and n‐paraffin this value must then also be equal to that for polyethylene in bulk. It may be concluded that, within experimental error, semi‐ordering effects in the melt are absent and that no specific diluent effects exist.
Examination of kinetics of graft copolymerization on preirradiated polymethyl methacrylate
Authors: Turska E. , Połowiński S.
Published: April 2003

The kinetics of graft copolymerization of vinyl acetate on polymethyl methacrylate has been investigated. Polymethyl methacrylate was preirradiated in the presence of air by γ‐rays, the polymer being used as the initiator of the polymerization in the one‐phase system. The rate of reaction for low conversion is proportional to the concentration of monomer raised to the power of 3/2 and to the concentration of initiator to the 1/2 power. The reaction satisfied the kinetic equation for ordinary addition polymerization if the decrease of the amount of the initiator during the process is taken into consideration. The activation energy of this process has been found. The quantity of the homopolymers produced in this reaction is negligible and need not be taken into account in rough calculations as far as kinetics are concerned.
On the additivity of osmotic properties of polyelectrolyte—salt solutions
Authors: Katchalsky A. , Alexandrowicz Z.
Published: April 2003

The simple additivity of osmotic pressure and ionic activity observed in polyelectrolyte—salt solutions is derived from a straightforward thermodynamic consideration. The basic assumption of this work is that the activity coefficient of the coions is practically uneffected by the presence of the largely screened polymeric ions.
Photosensitivity of dry‐heated polyacrylonitrile
Authors: Yoshino Tsuneo , Manabe Yasuo
Published: April 2003

Polyacrylonitrile heated under appropriate conditions (time and temperature) in nitrogen or in vacuo was found to be photosensitive. On exposure to visible light, the visible light absorption of a heat‐treated polyacrylonitrile film shifts to longer wave length, and an ESR absorption is detected in heat‐treated powder. Solubility to acids changes on exposure to light, and acids of appropriate concentration dissolve only the unexposed portion of a polyacrylonitrile film and leave the exposed portion. The relation between these effects of light on dry‐heated polyacrylonitrile is discussed.
Radiation dosimetry in polyethylene with silicon solar cells
Authors: Salovey R. , Rosenzweig W.
Published: April 2003

Irradiation dose rates and complete depth—dose curves in polyethylene have been directly determined with a silicon solar cell. In this manner, an average dose rate of 0.297 Mrad/sec. per incident μamp./cm.2 for 1 m.e.v. electrons in 120‐mil thick Marlex polyethylene was measured. The corresponding dose rate ascertained by ferrous sulfate dosimetry is 0.260 Mrad/sec. This difference is in the expected direction and may arise from differences in backscatter between polyethylene and silicon. The facility of the solar cell measurement and the complete definition of irradiation dose as a function of absorber thickness commend the device for general application in irradiation dosimetry.
Relative reactivity ratios for two new 2‐chloro‐1,3‐butadiene systems
Authors: Wich G. S. , Brodoway N.
Published: April 2003

The relative reactivity ratios in free‐radical, emulsion copolymerizations for the systems 2‐chloro‐1,3‐butadiene/methyl isopropenyl ketone and 2‐chloro‐1,3‐butadiene/methacrylic acid were found to be 3.6 and 0.1 and 2.68 and 0.15, respectively. Consequently, copolymers are formed substantially richer in 2‐chloro‐1,3‐butadiene units than the comonomer feed, have little alternation tendency, and do not form azeotropes. Distributions of monomer units in the copolymers are described.
Poly(4‐methyl pentene): X‐ray measurement of crystalline density and observation of a structural anomaly
Authors: Litt Morton
Published: April 2003

The unit cell of annealed poly(4‐methyl pentene) was measured by x‐rays; the unit cell is tetragonal with a = b = 18.50 ± 0.03 A. and c = 13.76 ± 0.07 A., which leads to a crystalline density of 0.832. This is lower than the density of the quenched polymers. Previous workers have postulated a 72 helix for the polymer. A reflection of 001 was observed consistently, which is forbidden for this helix. A superficial investigation indicates that the polymer crystallizes in a helical form but probably the side groups are displaced from a helical arrangement because of interference by neighboring side groups.
Nuclear magnetic resonance in solid polypyrrolidone
Authors: Filipovich G.
Published: April 2003

Nuclear magnetic resonance in solid poly‐2‐pyrrolidone has been studied over the temperature range 77–450°K. Experimental evidence concerning the differently ordered regions that contribute to the composite NMR curves has been obtained. Experimental techniques and results are described in detail. A detailed comparative interpretation of two‐component NMR curves as a function of temperature is offered in terms of motion in differently ordered regions. The width of the component corresponding to the crystalline regions was found to be independent of temperature over a certain range above that of liquid nitrogen; this is taken to indicate a rigid structure. At higher temperatures there is a gradual decrease in line width indicating increasing segmental molecular motion. The NMR line width representing amorphous regions was found not to change over approximately the same range of low temperatures; it then decreases faster with increasing temperature than that of the crystalline regions; it finally decreased sharply and became the narrow component above the glass transition temperature. The glass transition temperature in polypyrrolidone appears to decrease with increasing water content. Comparison of the temperature of glass transition of dry polypyrrolidone with those of other polyamides supports the observation that the temperature of this transition is lower, the smaller is the ratio of NH groups to methylene groups in a polyamide. Empirical second moment values at liquid nitrogen temperature and at room temperature, as well as an estimate of theoretical second moment for an assumed sheet model, are reported.
Interactions of low molecular weight compounds with solid polymers
Authors: Kryszewski Marian , Skorko Marta
Published: April 2003

In order to establish the kind of dispersion of low molecular weight compounds in solid polymers the absorption spectra of their solutions in liquid monomer and solid polymer were investigated. On this basis the oscillator strengths were calculated for solutions of the light stabilizers, 5‐chloro‐2‐hydroxybenzophenone phenyl salicylate, and 1‐naphthylamine in monomer and polymer. The change of oscillator strength is related to the change of dispersion character. Styrene and polystyrene were used as solvents. The hydroxybenzophenone and salicylate show molecular dispersion in the case of thermal polymerization, and are slightly incorporated into the chains during the initiated polymerization. Naphthylamine is incorporated into the chains in a higher degree. Besides it was stated that the oscillator strength is almost independent of conversion degree. If the incorporation of investigated substance into the chains takes place it occurs during the entire polymerization process.
Molecular configuration of polystyrene in benzene
Authors: Debye P. , Chu B. , Kaufmann H.
Published: April 2003

The particle scattering factor P(ϑ) with Gaussian statistics for polydispersed systems has been treated. For a polystyrene sample with a sharp molecular weight distribution (Mw/Mn < 1.02, Mw = 1.5 X 106), the measured angular dependence of scattered intensity indicates that the polymer coil does obey Gaussian statistics. This holds for a range of concentrations provided the variation of the constant representing the radius of gyration with concentration is adjusted.
Competing side reactions in the polymerization of α‐olefins by ziegler‐natta catalysts
Authors: Ketley A. D. , Moyer J. D.
Published: April 2003

The polymerization of 3‐methylbutene‐1 by TiCl3–Al(C2H5)3 catalysts in dilute solution above 80°C. yields a polymer which is contaminated with polyethylene. By using tagged aluminum alkyl, this polyethylene was shown to arise almost wholly by displacement of ethylene from the alkyl by the monomer. This side reaction was shown to be a general one in the polymerization of α‐olefins other than propylene at elevated temperatures. Analysis of the gas phase above the reaction showed also that some decomposition of the monomer occurs under these conditions.
Use of dimaleimides as accelerators for the radiation‐induced vulcanization of hydrocarbon polymers. Part II. Synthetic rubbers and saturated polymers
Authors: Miller S. M. , Spindler M. W. , Vale R. L.
Published: April 2003

The effect ofm‐phenylenedimaleimide on the rate of cross linking of synthetic rubbers, polyvinyl acetate, polyvinyl chloride, polyethylene, and other polymers, under the action of ionizing radiation is described. The dose reduction factor for equivalent degrees of crosslinking obtained with and without the maleimide varies from 10 to 25 for the synthetic rubber. Further evidence is given to show that maleimides sensitize the vulcanization of unsaturated polymers, principally by copolymerization, and certain saturated polymers containing labile atoms, by a transfer mechanism.
Infrared spectra and assignments for polyvinyl chloride and deuterated analogs
Authors: Krimm S. , Folt V. L. , Shipman J. J. , Berens A. R.
Published: April 2003

Deuterated analogs of polyvinyl chloride (PVC) have been prepared and their infrared spectra analyzed as an aid to the more detailed assignment of bands in the spectrum of PVC. The following deuterated polymers were studied: PVC‐αd1, PVC‐βd1, PVC‐αβd2, and PVC‐d3. These, as well as PVC, were polymerized in urea‐complex, at −78°C., and at +50°C. in order to determine which bands are of crystalline origin and which of noncrystalline origin. Polarized spectra of oriented samples were obtained in each case to assist in the analysis. As a result of this study several of the previously uncertain assignments have been clarified. With the help of other studies on model chlorine‐containing compounds it has been possible to identify the various conformations present in the polymer and to associate these with isotactic and syndiotactic pair configurations in the chain. A method is suggested for determining the proportion of each type of pair configuration in PVC.
Study of entanglement of polymers in solution by viscosity measurements. II. Polymethyl methacrylate in various solvents
Authors: Maron Samuel H. , Chiu Thomas T.
Published: April 2003

A study has been made of the flow behavior at 30°C. of solutions of three samples of polymethyl methacrylate in three solvents in both the Newtonian and non‐Newtonian regions. The concentration range covered was approximately 0–16% by weight. By application of the Ree‐Eyring theory it was found possible to represent the observed data in terms of two flow units, and to obtain from the parameters of the theory the effective hydrodynamic volume occupied by the polymer in solution, ευ2. Here υ2 is the volume fraction of the polymer and ε an effective volume factor. The volume factor, ε, was found to be dependent on both solvent and molecular weight only up to ca. υ2 = 0.04. Beyond υ2 = 0.04, ε is independent of solvent and is a function of molecular weight only. These observations indicate that chain entanglement in solution is not probable. Rather, the polymer chain curls on itself, and compacts to a small mass when the effective concentration ευ2 = 1 and the viscosity becomes infinite. The concentration at which this occurs, υ∞, is given by ∞ = 1/ε∞. The quantity ε∞ has been found to be a linear function of molecular weight, M. Further, the value of ε at υ2 = 0, ε0, has been found to be an exponential function of M, and to yield expressions relating intrinsic viscosity to molecular weight in good accord with published results.
Further NMR studies of polydimethylsiloxanes: Effects of radiation‐induced crosslinking
Authors: Huggins C. M. , St. Pierre L. E. , Bueche A. M.
Published: April 2003

Previous nuclear magnetic resonance measurements on a polymethylsiloxane gum (MW = 75,000) had been interpreted to indicate the presence of considerable segmental motion in both the amorphous and crystalline components at temperatures above the glass temperature. Further investigation again showed the NMR line to be completely narrowed just above the glass point indicating such motions must extend into the crystalline component. This work was extended by the measurement of NMR absorption line widths for temperatures of 80–300°K. on samples of the same gum subjected to gradually‐increased crosslinking by electron doses of 3–600 × 106 rep. Here, no change in the NMR properties of low temperature, rigid states were observed, but the room temperature line width progressively increased from 0.019 gauss to over 0.100 gauss peak‐to‐peak due to the increase in bulk viscosity of the liquid. The “first‐order” activation energy associated with the temperature‐dependent line narrowing decreased from 10 to 2 kcal./mole. The NMR data indicate that the primary effects of radiation‐induced crosslinking are to reduce the chain rotational energy by the creation of defects and to increase the short‐range viscosity by the lowering of translational freedom.
An improved ebullioscope for high polymers
Authors: Arnett Raymond L. , Smith Melvin E. , Buell Barry O.
Published: April 2003

A description is given of an ebullioscope which was calibrated and found satisfactory for determining the number‐average molecular weight of several unbranched polyethylenes. It employs a benzene‐filled Menzies differential vapor pressure thermometer having a detection limit of 5 × 10‐6°C. In order to obtain a close approach to solvent—vapor and solution—vapor equilibria, the boiler design incorporates a means of preheating the liquid solvent returning from the condenser and a mechanical lift pump to extract liquid solution from the boiler. In addition, time stability of these equilibria is provided by insulation to reduce heat conduction, reflectors to exclude radiant energy, constant pressure control, and constant wall temperature. An analysis of the observed temperature fluctuations shows that these features result in thermometer noise which is lower by an order of magnitude than any heretofore reported. Full advantage from this improvement has not been realized in interrupted (3‐day) experimental runs which gave a standard deviation of 400 at the 10,000 molecular weight level. Indications are that full benefit of the reduced thermometer noise with severalfold further reduction in standard deviation, could be realized in uninterrupted runs.
Crystallization and melting behavior of polyacrylonitrile
Authors: Chiang R.
Published: April 2003

Dilatometric measurements have been carried out on the crystallization of poly‐acrylonitrile from propylene carbonate solutions at concentrations of 1.0, 4.2, and 8.4% and temperatures of 40, 70, 95, 104, and 108°C. Contrary to expectation, the volume of the solution actually increases upon crystallization, although the increase is extremely small (about 1% based on polymer). This small change in volume is consistent with the partial specific volume of polyacrylonitrile in solution and the specific volume of the polymer measured directly by a flotation method. Recent investigation by Holland, et al. revealed that polyacrylonitrile, upon crystallization from dilute solution, forms crystalline platelets resembling the single crystals observed in other polymers. It appears that the small change in volume on transformation from the dissolved state into the crystalline state is due to the closeness of the specific volumes in the two different states. These unusual density data of polyacrylonitrile resemble those of poly(methyl‐methacrylate), where isotactic, syndiotactic, and atactic polymers have about the same density. The fact that the difference in density of polyacrylonitrile is so small might well explain a number of related phenomena: the lack of abrupt volume change on melting, the absence of amorphous regions, the narrow range of the density values of different samples prepared by different methods, and the fact that crystallization conditions exert practically no effect on the density of the sample.
Effect of ions on the dielectric dispersion of ovalbumin solution
Authors: Takashima Shiro
Published: April 2003

The dielectric dispersion of ovalbumin solution was studied in the presence of various ions. It was found that ions such as tetraethylammonium, ammonium, Na, and K which are not bound to the protein had no effect on the dielectric increment or on the relaxation time. On the contrary, the addition of ions such as Cu, Ca, Mg, and H ions had a considerable effect on the dielectric increment as well as on the binding of the ions to the protein. These results indicate that ions do not affect the dielectric dispersion parameters of this protein unless they have specific interaction with the polar sites of the ovalbumin molecule. The electric polarization of protein solutions is discussed and it is suggested that the ion fluctuation process including the Maxwell‐Wagner effect is not necessarily the essential mechanism of dielectric polarization of isoelectric protein solutions.
Tracer techniques for the determination of monomer reactivity ratios. IV. Monomer reactivity ratios for styrene–isoprene copolymerization
Authors: Wiley Richard H. , Davis Burns
Published: April 2003

The ionization chamber‐vibrating reed electrometer assay technique has been improved in precision (±0.25% average deviation) and used to determine monomer reactivity ratios for the styrene—isoprene copolymerization. Values of r1 (styrene) = 0.50 (100°) and 0.54 (80°) and r2 = 1.92 (100°, 80°) have been obtained for the radical initiated copolymerization. For γ‐irradiation initiation at 22°, r1 = 0.66 and r2 = 1.88. For butyllithium initiation, r1 = 0.03 and r2 = 5.9. The difference in the radical and γ‐radiation initiation values is considered in terms of possible partial ionic character of the radiation initiation process and possible temperature dependence of the reactivity ratios (r1) over the 22–100°C. range. The latter indicates a difference in activation energy of 0.8 kcal./mole for the radical to styrene and radical to isoprene propagation steps.
Proton magnetic resonance in natural rubber: Comparison with dielectric measurements
Authors: Kusumoto Hazime , Gutowsky H. S.
Published: April 2003

Proton magnetic resonance studies have been made of cured natural rubber containing up to 31% combined sulfur. Line shapes and spin‐lattice relaxation times were observed at temperatures between —190 and 180°C. In the line shape studies, the main effect of the combined sulfur was upon the temperature at which the line width is narrowed by the molecular segmental motions. The temperature at the onset of the major line width narrowing increases from —50°C. for raw rubber to about 10°C. for 31% combined sulfur. A relation was found between the dependence upon sulfur content of the line width changes and the second‐order transition temperature. The proton spinlattice relaxation timeT1was measured for three cured samples in the temperature range above the motional narrowing region. TheT1vs. temperature curves agree qualitatively with the theory of Kubo and Tomita. The general features of theT1curves are consistent with a distribution of correlation times which broadens with increasing sulfur content. Energies of activation were computed from these results and they are compared with the dielectric relaxation data obtained previously. The effect of a distribution of correlation time is discussed.
Conductivity and viscosity measurements on sodium polyacrylates of different molecular weights
Authors: Packter A.
Published: April 2003

Combined conductivity and viscosity measurements have been carried out on a series of sodium polyacrylate solutions of different molecular weights with viscosities varying from 1.1 to 40 c.p. Analysis of the measurements indicates that ionic mobilities in polyelectrolyte solutions are not affected by overall solution viscosity; i.e., the Walden rule is not applicable to such solutions.
The branching reaction. III. Polymeric transfer constants of vinyl acetate with styrene and methyl methacrylate
Authors: Morton Maurice , Piirma Irja
Published: April 2003

A study has been carried out to determine the polymeric transfer constants of poly(vinyl acetate), polystyrene, and poly(methyl methacrylate) in the polymerization of vinyl acetate, as well as the similar transfer constants of poly(vinyl acetate) in the polymerization of styrene and methyl methacrylate. As before, this was accomplished by polymerizing each monomer in the presence of varying amounts of the desired oligomer and separating the resulting polymers. The effect of oligomer endgroups was checked by using oligomers of different molecular weight (1000–5000). As found previously for styrene and methyl methacrylate, there was no noticeable effect of polymeric endgroups on transfer activity, hence the transfer constants found refer to the interior units in the chain. The values of the various transfer constants are given. As expected, the vinyl acetate radical showed a reactivity in hydrogen abstraction which was several orders of magnitude greater than that of the styrene radical, and at least one order of magnitude greater than that of methyl methacrylate. The absolute values of the activation energy for the transfer step were remarkably similar, the difference in transfer activity being largely due to the difference in activation energy of the propagation reaction, and also to steric considerations.
Aromatic polyimides
Authors: Bower G. M. , Frost L. W.
Published: April 2003

Aromatic polyimides were prepared in two steps. Pyromellitic dianhy dride was added to a solution of an aromatic diamine in a highly polar solvent, such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, or N‐methyl‐2‐pyrrolidone, until a high molecular weight polypyromellitamic acid was obtained. The amount of pyromellitic dianhydride required was determined by the rate of viscosity increase with addition of the reagent, and it corresponded fairly closely to the stoichiometric quantity. Inherent viscosity of the polypyromellitamic acids in dimethylacetamide ranged from 0.54 to 3.22. Upon standing at room temperature, the viscosity of these solutions gradually declines. This viscosity decline is rapidly accelerated by an increase in temperature and is negligible at 0°C. Water and excess pyromellitic dianhydride result in a more rapid decline in viscosity. The polypyromellitimides were formed from the amide acids by heating. The solvent could be removed during the imidization step or earlier under vacuum at a lower temperature. Polypyromellitimides were prepared from m‐phenylenediamine, benzidine, 4,4′‐diaminodiphenyl ether, 3,4′‐diaminodiphenyl ether, 4,4′‐diaminodiphenyl sulfide, methylene dianiline, isopropylidene dianiline, several diaminobenzanilides, 4,4′‐diaminophenyl benzoate, and other amineterminated low molecular weight aromatic esters and amides. Polyimides cast in the form of thin films were for the most part clear, tough, flexible, insoluble, and infusible. Thick sections tended to be brittle and opaque. Several of the polymers in the form of films suffered less than 10% weight loss after aging 400 hr. at 325°C. in air. Most of these films were still intact and moderately flexible after this treatment.
Donor‐acceptor interaction in cationic polymerization. V. Influence of some alcohols on the molecular weight of polyisobutylene in polymerization catalyzed by aluminum trichloride
Authors: Zlámal Z. , Kazda A.
Published: April 2003

AlCl3 in ethyl chloride at −78.5°C. forms with lower aliphatic alcohols (MeOH, EtOH, i‐PrOH, tert‐BuOH) complexes of the type 4ROH · AlCl3, 2ROH · AlCl3, ROH · AlCl3 and ROH · AlCl6. The existence of these complexes was established from the conductivity—composition graphs of corresponding ROH‐AlCl3 systems. These complexes are ionized to different degrees and their ability to catalyze the polymerization of isobutylene is proportional to the acidity of the alcohol forming the complex. Phenol differs somewhat in its behavior. The conductivity‐composition plot reveals the existence of complexes of the type 3C6H5OH · AlCl3, 2C6H5OH · AlCl3, and C6H5OH · AlCl3. The catalytic activity of complexes containing phenol and AlCl3 is considerably higher than that of complexes involving aliphatic alcohols. The dependence of the molecular weight of polyisobutylene on the composition of the active complex is a mirror image of the conductivity graph. The rate of termination reactions changes with both concentration and quality of anions present. The termination activity of anions derived from phenol and containing OC6H5 group is considerably higher than the termination activity of anions derived from aliphatic alcohols.
An application of the prigogine solution theory to intrinsic viscosities in polyisobutylene‐n‐alkane systems
Authors: Bataille P. , Patterson D.
Published: April 2003

Intrinsic viscosities have been obtained for polyisobutylene in the series of n‐alkane solvents at −12, 24.3, and 57.9°C. Values of the χ parameter have been calculated using [η]/[η]ϑ = α2.43 and the Flory closed expression relating α to χ (as modified by Stockmayer): α5 — α3 = 2 × 0.49 CMM1/2 [(1/2) — χ]. The values found by the first method are in excellent agreement with an approximate expression for χ derived using the Prigogine theory of polymer solutions, viz. Rχ = ArA/T + BT/rA where rA is the number of segments in the solvent molecule. Values of the constants A and B compare well with those found from heats of mixing of polyisobutylene with the same solvents. Values of χ are also obtained using the more recently Kurata‐Stockmayer‐Roig expression for the α — χ dependence although reasons are advanced for preferring the Flory‐Stockmayer equation. Qualitative, but less good quantitative agreement is now found between the χ values and the Prigogine theory.
Monomers containing phosphorus. Part II. Copolymerization of diallyl phenyl phosphine oxide with n‐lauryl methacrylate
Authors: Beynon K. I.
Published: April 2003

Monomer reactivity ratios have been measured for the copolymerization of n‐lauryl methacrylate with diallylphenylphosphine oxide at 80, 110, and 140°C. The n‐lauryl methacrylate is far more reactive in the copolymerization than the diallylphenylphosphine oxide. The reactivity ratios at 140°C. as calculated by the Mayo and Walling integrated equation vary with the composition of the starting mixture in the copolymerization, and the value of r2 is significantly negative. These effects are explained by the existence of a penultimate group effect produced by diallylphenylphosphine oxide.
Interactions of polyelectrolytes. A turbidimetric method for the estimation of ionized polymers
Authors: Josephs R. , Feitelson J.
Published: April 2003

The turbidity resulting from the interaction of protamine with negatively charged polymers in solution was adapted to the micro estimation of the latter. The influence of pH, salt concentration, and valency as well as protamine concentration and time dependence was investigated in the protamine—polymethacrylic acid system and the optimal conditions for turbidimetry were established. Amounts of down to 2 × 107−7 monomoles of polymer were conveniently measured. The method is usable over a wide pH range but is sensitive to the added salt or buffer concentration. The changes in turbidity as a function of the above mentioned variables are qualitatively explained in terms of polyelectrolyte interaction complexes and screeing of the aggregate charges by added electrolyte. The method was also tested for its applicability to the estimation of polyglutamic acid.
Coordination compounds of p‐nitrobenzeneazotyrosine
Authors: Mattison Louis E. , Phipps Martha S. , Alfred Lillian , Taylor Sally , Thompson John , Saul Barry
Published: April 2003

In continuation of earlier work, another chelating agent containing two different chelating systems in the same molecule (p‐nitrobenzeneazotyrosine) was synthesized. 2:1 coordination monomers of this molecule were made and characterized with divalent copper, lead, cobalt, nickel, uranyl, and zinc ions. From these compounds, two types of coordination polymers were synthesized and studied: those involving the ions of one metal bound with both chelating groups in the ligand, and those having two different metals bound in the same polymer chain. Thermal analysis data showed that (among the group under consideration) the bimetallic polymeric chelates have no exceptional stability.
Molecular properties of amorphous high polymers. I. A cell theory for amorphous high polymers
Authors: DiBenedetto A. T.
Published: April 2003

A cell model is used to describe the structure‐insensitive properties of amorphous high polymers. An amorphous polymer is characterized as a homogeneous, one‐component phase containing N identical n‐center polymer segments. Each center is acted on by a cylindrically symmetric square well potential which is developed by assuming a 6–12 type interaction between point centers along the axis of the polymer chain. Molecular constants, p‐V‐T behavior, glass‐transition temperatures, and cohesion energy densities are predicted from a minimum of experimental data. A good agreement between theory and experimental data from various literature sources is shown for eight amorphous polymers.
Synergistic antioxidant combinations. Carbon black substitutes
Authors: Hawkins W. L. , Worthington M. A.
Published: April 2003

Alkylated diphenoquinones form synergistic antioxidant combinations with sulfur and a variety of organosulfur compounds. In combination with thiols, reduction of the diphenoquinones to their corresponding diphenols occurs, and these phenols are also synergistic with sulfur compounds. Secondary amines including N,N'‐diphenyl‐p‐phenylenediamine and the diimine formed by its oxidation function similarly as do the polyacenes. Synergism with these antioxidant systems may result from regeneration of a phenol or a secondary amine as the active chain terminator. The effectiveness of these antioxidant combinations suggests, however, that additional stabilization reactions may occur involving the sulfur component.