bluuebunny/crossref_metadata_2025 huggingface dataset:
Comments on intrinsic viscosity–weight‐average molecular weight relationships for polyethylene
Authors: Chiang R.
Published: April 2003

Relationships, as reported in the literature, between intrinsic viscosity and weight‐average molecular weight for high‐density polyethylene are in poor agreement. Experimental work in this laboratory, aimed at resolving similarly conflicting data, suggests that likely causes for these discrepancies are: polydispersity, incorrect dissymmetry correction, and inadequate solution clarification. These factors are discussed in some detail, and results on both fractionated and unfractionated samples support these conclusions. It is apparent that fairly narrow fractions must be studied to obtain a valid intrinsic viscosity‐weight‐average molecular weight relationship.
Swelling and elasticity of irradiated polydimethylsiloxanes
Authors: St. Pierre L. E. , Dewhurst H. A. , Bueche A. M.
Published: April 2003

The G value for crosslinking of polydimethylsiloxanes by high energy electrons has been redetermined using cryoscopc methods and checked by quantitative determinations of the amounts of gases evolved. The value found, G = 2.5 ± 0.4, is significantly different from that reported previously. The swelling of high polymers crosslinked by high energy electron has been measured using benzene and toluene. The x1 value calculated using equilibrium tension and swelling measurements are in good agreement with those obtained from the vapor pressure measurements of Newing. The equilibrium tension measurements indicate that 1 mole of crosslinks produces 1.3 ± 0.3 moles of effective chain between crosslinks in the Wall, Flory, Rehner scheme. This is in agreement with the predictions of Guth and James.
Molecular weights of sugar beet araban fractions
Authors: Tomimatsu Yoshio , Palmer K. J. , Goodban A. E. , Ward W. H.
Published: April 2003

The molecular weight of sugar beet araban fractions prepared by fractionation of the araban acetates on a charcoal column have been determined. Light‐scattering measurements using 2 M NaCl and aqueous 1% N,N‐dimethylformamide (DMF) as solvents gave, weight average molecular weights which did not agree, the values in the latter solvent being about half of those in the former. Other experimental observations, such as, number average and sedimentation‐viscosity molecular weights favor the results in salt solution; the low results in 1% DMF are presumably due to the interaction between araban and DMF. Arabans exhibited appreciable fluorescence when incident light of wavelength 436 mμ was used, but none at λ = 546 mμ. Sample limitations prevented measurements at the higher wavelength, and an alternate procedure for correcting for fluorescence is presented. The weight average molecular weights in 2 M NaCI which ranged from 18,400 to 37,000 for this study are appreciably higher than the previously reported value of 10,000. Number‐average molecular weights determined by the chlorous acid end‐group method ranged from 8700 to 24,200 for the various fractions. No simple relationship between molecular weight and fraction number was observed, and most of the fractions showed appreciable molecular weight heterogeneity.
Study of particles present in some high‐pressure polyethylenes
Authors: Moore Louis D. , Peck Virgil G.
Published: April 2003

Scattering of light by solutions of high‐pressure polyethylenes reveals that very large particles are present. These particles are not quantitatively removed by filters having a rated pore size of a fraction of a micron. If these particles are foreign material, aggregates of molecules, they probably should be removed before the solutions are studied in order to avoid an erroneous interpretation of the light‐scattering data. If, however, they are actually molecules of polyethylene, in most cases they should not be excluded from study because, in so doing, the results would not truly represent the sample. Experimental evidence is adduced to show that the particles are not foreign material, aggregates of molecules, or microgel. By appropriate techniques, very thin films of polyethylene can be cast from solution. By etching and shadowing these films, electron photomicrographs revealing the physical appearance of the particles may be obtained. Their shape, solubility, and behavior on pyrolysis strongly indicate that the particles are actually polyethylene molecules of very high molecular weight—perhaps 40,000,000. Such molecules might form an important part of the over‐all molecular‐weight distribution and, therefore, should not be excluded from studies of solutions by light scattering. Electron microscopy proved useful in offering visual confirmation that the particles present in the solutions used for light scattering are actually molecules. Also, it is quite probable that these photomicrographs show the largest polyethylene molecules which have ever been observed individually and reported.
Thermal degradation of polyethylene oxide and polypropylene oxide
Authors: Madorsicy S. L. , Straus S.
Published: April 2003

Polyethylene oxide and atactic and isotactic polypropylene oxides were pyrolyzed in a vacuum in the temperature range 265 to 363°C. One phase of the investigation consisted in fractionating the products of degradation and analyzing the fractions qualitatively and quantitatively. Another phase consisted in measuring rates of degradation and calculating from these rates the activation energies. As compared with the corresponding non‐oxide polymers, polyethylene and polypropylene, the oxide polymers are less stable thermally, yield larger amounts of monomeric fragments, and have lower activation energies.
An x‐ray study of new cellulose complexes with diamines containing three, five, six, seven, and eight carbon atoms
Authors: Creely Joseph J. , Segal Leon , Loeb Leopold
Published: April 2003

Five new diamine‐cellulose complexes have been prepared from cotton by means of tri‐, penta‐, hexa‐, hepta‐, and octamethylenediamines. The diamine contents of the dry fibrous materials have been determined, and the characteristic x‐ray diffractometer tracings have been obtained. Satisfactory x‐ray fiber patterns could not be obtained for the hydrazine, hepta‐, and octamethylenediamine complexes. The distention of the 101 interplanar spacing was found to be related linearly to the number of carbon atoms in the diamine molecule. Intensity of the diffraction also increased markedly with diamme chain length. Unit cell dimensions of the new complexes have been calculated. The x‐ray data indicating that the 101 interplanar spacing is occupied by only one diamine molecule is supported by the analytical data showing a diamine content close to that required by an anhydroglucose‐diamine ratio of 2:1.
Crystal structures in polyamides made from ω‐amino acids
Authors: Slichter W. P.
Published: April 2003

The crystal structures of several polyamides made from ω‐aminocarboxylic acids have been studied at room temperature by x‐ray diffraction. Previous workers have reported structures for only two members of the series, polycaproamide (nylon 6) and polyundecamide (nylon 11). It is found that the amino acid polymers fall into two main groups. Those which are made from monomers containing an odd number of carbon atoms are reminiscent of the triclinic structures found with the even‐even diamine‐dioic acid polyamides. Those which are made from amino acids having an even number of carbon atoms recall the hexagonal structures of the odd‐odd diamine‐dioic acid polymers. Evidently the preference for one crystal form over the other depends largely upon details of the coupling between amide groups on neighboring chains. The molecular arrays found in crystallites apparently occur to an important degree in the melt. Models for the molecular arrangements are discussed. Polycaproamide, hitherto the most widely studied member of the series, appears to be anomalous in its crystal structure.
A tracer study of the polymerization of vinyl chloride by redox catalysis
Authors: Firsching F. H. , Rosen Irving
Published: April 2003

A study was made of the polymerization of vinyl chloride using radioactive NaHS35O3 and KCl36O3 in a redox catalyst system. The object was to determine the fate of the catalysts as an aid to understanding part of the process of radical production and of the initiation of the polymerization. With the catalyst concentration usually used to conduct polymerizations, 0.3 atom of catalyst sulfur and about 0.08 atom of catalyst chlorine are chemically bound per PVC molecule. Increasing the catalyst concentration causes an increase in both the catalyst sulfur and catalyst chlorine incorporated into the PVC. The incorporation of the catalyst sulfur into the PVC, and the role of the sulfite in initiating the polymerization, can be explained by the free radical mechanism postulated for the addition of bisulfite to olefinic bonds. Only one‐tenth of the catalyst chlorine bound to the PVC comes from the hypochlorite intermediate formed during the reaction. This suggests that the reactions of the sulfite with the chlorate, and with the chlorite formed during the reaction, produce most of the chain‐initiating radicals.
Electron microscope‐electron diffraction investigations of the crystalline texture of polyamides
Authors: Keller A. , Keller A. , Engleman R.
Published: April 2003

Continuous films and discontinuous aggregates of nylons were prepared and examined with combined electron diffraction and electron microscope techniques. It was found that the electrons destroy the diffracting ability of the crystals without affecting their shape. The consequences of this fact for the electron microscopy of polymers are pointed out. It was found that the molecules and the planes containing the hydrogen bonds tend to lie in the film plane, but deviations from this orientation amounting to a maximum of 25° were also found. An expression is derived for establishing the fiber axis direction from single, tilted electron‐diffraction patterns. In some films, a spherulitic morphology was observed which consists of a flat layer structure within the film plane. In general, however, the spherulites develop through a fibrous texture, which appears to arise through the curling up of flat sheets. These sheets themselves possess a fibrous morphology. The spherulitic orientation, as established previously by x‐rays, could now be identified within submicroscopic fibrous aggregates. By examination of individual sheaves in the selected area we could identify ribbons and fibrils which can be considered as being the equivalents of single crystals. The molecules were found to be lying at large angles to the length of even the smallest fibrils. The conclusion was reached that this requires a regular, sharply folded configuration of the molecules, which would also account for the uniform width of the microfibrils. The implications of this new concept are discussed, and earlier models are reviewed in the light of the new facts.
An investigation, with the Weissenberg rheogoniometer, of the stress distribution in flowing polyisobutylene solutions at various concentrations and molecular weights
Authors: Jobling A. , Roberts J. E.
Published: April 2003

The flow properties of a series of tetralin solutions of polyisobutylene are examined with the Weissenberg rheogoniometer. The general form of the stress distribution in laminar flow is the same as that observed previously in other viscoelastic materials, the primary phenomenon being an additional normal tension in the direction of flow. The effects of rate of shear and of polymer concentration and molecular weight on this stress distribution are investigated. The shear elasticity increases markedly with increasing rate of shear in the less elastic liquids and drops slightly with increasing rate of shear in the more elastic solutions. The apparent viscosity drops with increasing rate of shear in all the solutions examined, but only a minor part of this fall can be accounted for by the correction for the angular deviation of the main directions of stress and strain velocity at high rates of strain.
CH2 Rocking vibrations and the structure of polyethylene glycols
Authors: Kuroda Yoko , Kubo Masaji
Published: April 2003

The infrared absorptions of polyethylene glycols of various degrees of polymerization from a 14‐mer to a 90‐mer in pure liquid state, in benzene solutions, and in thin solid films were recorded. The data bridge with gradual changes of spectral patterns the transition between the absorptions due to CH2‐rocking modes of lower members and those of crystalline high polymer of this series. This enables one to make unequivocal assignments of observed frequencies to the normal modes of an O(CH2)2O unit capable of assuming either gauche or trans configuration. The band at about 845 cm.−1 is a crystalline band, while those at about 885 and 863 cm.−1 are amorphous bands. The absorption at about 948 cm.−1 splits into doublets in crystalline high polymers. The gradual changes in spectral features with‐degree of polymerization show how the helical structure of high members of this polymer series changes into less regular structures of the lower members.
Sound velocity in polyethylene
Authors: Schuyer J.
Published: April 2003

According to Wada and Yamamoto the factor A, which occurs in the Rama Rao empirical relationship: (1/v)(dv1/dT) = (A/p)(dp/dT) (v = sound velocity, p = density, and T = temperature) is for solid polymers much greater than 3, which value holds for liquids. This relationship is discussed in the present paper. The A appears to be a simple function of the powers n and m of the intermolecular distance in the equation for the interaction potential, viz., A = (m + n + 1)/6, from which it follows that in the Lennard‐Jones potential (where m = 12 and n = 6) A = 3.17. Furthermore, it has been established that Rama Rao's relationship is a special case of the general equation

(vl = longitudinal sound velocity, σ = Poisson ratio) for σ = ½, i.e., for liquids. From experiments on a number of polyethylene samples it was shown that the value of A thus corrected is about 3, whereas the uncorrected values vary from 5 to 9. The conclusion is that the specific sound velocity in its general form is described by (v1/3/ρ) [(1 + σ)/3(1 − σ)]1/6, and it has been found from experiments that the values thus calculated for polyethylene samples are equal to those for amorphous polyethylene derived from measurements on liquids. Finally, the elastic constants derived from the experimental results are plotted versus the density values in the range from amorphous to crystalline polyethylene at a frequency of 2 mcycle/sec. and a temperature of 20°C.
Ultracentrifuge and related studies on oxidized wool keratin
Authors: Peacock N. , O'Callaghan F.
Published: April 2003

Investigations have been made into the sedimentation behavior of solutions prepared by oxidizing Lincoln and Merino wools in peracetic acid and then extracting in 0.15 N ammonium hydroxide solution. There was no apparent difference between the extracts from the two types of wool. The sedimentation pattern showed two peaks of a s ∼ 2S and 1S. The α‐keratose, which was precipitated by acidification, showed a similar 2‐peak pattern to the original solution, but the amount of the faster component was enhanced. The α‐keratose was in the a form, but was partially converted to the α form on treatment in water at 40°C. Fractionation of α‐keratose has been carried out from ammonium hydroxide solution, urea solution, and ithium bromide solution. From the first two of these, products have been obtained which contain a high proportion of α1‐keratose. The sedimentation coefficient of α1‐keratose in ammonium hydroxide at pH 10.5–11 has been determined to be 2.60S at infinite dilution. The effect of storage of the solutions at 18–25°C. is to reduce the amount of α1‐keratose and to produce a precipitable component in the β form. In view of this and other obvious signs of degradation, caution must be exercised in interpreting the soluble components in terms of components in the original wool fibers. The dissolution apparently does not differentiate between the ortho‐like and para‐like material in the wool cortex, and α‐keratose therefore represents a component fundamental to both.
Kinetics of the gamma‐induced graft copolymerization of vinyl acetate to Teflon
Authors: Restaino A. J. , Reed W. N.
Published: April 2003

The gamma‐induced graft copolymerization of vinyl acetate to films of polytetrafluoroethylene is affected by hydroquinone. A study of the effect of polytetrafluoroethylene film thickness on the rate of grafting indicates that the weight of vinyl acetate grafted is independent of the film thickness. The rate of grafting is observed to be proportional to the three‐halves power of the monomer concentration from 2.0 to 10.8 molar vinyl acetate in ethyl acetate, and to the one‐half power of the intensity in the range investigated from 15,000 to 460,000 r/hr. After initial grafting there is an increase in the grafting rate. The addition of as much as 15 g./dl. of high molecular weight polyvinyl acetate to the copolymerization mixture has no effect on the initial rate of grafting. The activation energy is found to be 4.78 ± 0.32 kcal./mole (95% confidence limit). A mechanism consistent with these observations is presented. The addition of small quantities of carbon tetrachloride results in a decrease in the rate of grafting as well as a decrease in the molecular weight of the homopolymer formed. The decrease in grafting rate is attributed to a smaller G‐value for radical formation of carbon tetrachloride when compared to that for vinyl acetate and to the differential rate of chain transfer between carbon tetrachloride and grafted polyvinyl acetate with vinyl acetate radical. The chain transfer constant of carbon tetrachloride with vinyl acetate radical has been measured with the use of gamma‐rays to initiate polymerization. The value is 0.47.
Dynamics of branched polymer molecules in dilute solution
Authors: Zimm Bruno H. , Kilb Ralph W.
Published: April 2003

Theoretical formulas for the intrinsic viscosity and viscoelastic properties of some model branched molecules in dilute solution are calculated by means of the normal coordinate method of Rouse modified to include hydrodynamic interactions. The calculations are exact except for the usual approximation of the hydrodynamic interaction by the Kirkwood‐Riseman formula. The ratio of the intrinsic viscosity of a branched molecule to that of a linear molecule of the same weight is found to vary almost as the square root of the ratio of the mean square radii, instead of as the latter ratio to three‐halves power, as has been postulated before. It is proposed that this square root relation is applicable in general to branched molecules of all types. Several sets of experimental data in the literature are shown to agree well with this hypothesis.
Application of the archibald sedimentation principle to paucidisperse macromoleculaar systems
Authors: Erlander Stig R. , Foster Joseph F.
Published: April 2003

The authors have found experimentally that the initial slope of a Trautman plot of data obtained from sedimentation‐velocity experiments yields the z‐average molecular weight of the solute components. It is also well known that the weight‐average molecular weight is obtainable from such a plot. Equations are derived which permit the calculation of the individual concentrations and molecultar weight for unknown twocomponent paucidisperse systems. The experimental results on various two‐component protein mixtures are compared to known values. It was found that the ratio of the weight concentrations of two components must be within about one to five for accurate results. It may be possible to extend the method to multicomponent systems. One could then rapidly determine the size distribution of synthetic and natural heterogeneous polymers.
A viscometric criterion of polymer polydispersity
Authors: Frisch H. L. , Lundberg J. L.
Published: April 2003

An index of the molecular weight dispersity of a polymer is afforded by the ratio of viscosity‐average molecular weights in two different solvents. The index is proportional to the weight‐ to number‐average molecular weight ratio. The simplicity and ease with which this index can be experimentally obtained is bought to a certain extent by loss of reliability. Extensions of the proposed procedure leading to characterization of the molecular weight distribution are discussed.
Polymerization kinetics of acrylonitrile
Authors: Parts A. G.
Published: April 2003

It has been found that the polymerization of acrylonitrile dissolved in water proceeds easily in the presence of hydrogen peroxide and iron(III) salts. The kinetic investigation of this reaction shows that it is second order with respect to the monomer. The rate of reaction invreases with the concentration of hydrogen peroxide and of iron(III) salt but it decreases with an increase in the concentration of hydrogen ions. The average molecular weight of the formed polymer was determined by viscosity measurements. The degree of polymerisation increases with the concentration of the monomer and hydrogen ions, but decreases with an increase in the concentration of hydrogen peroxide and iron(III) salt. The reaction is inhibited by dissolved gaseous oxygen. Under otherwise similar conditions, the rate of the decomposition of hydrogen peroxide is considerably decreased in the presence of the acrylonitrile compared with its catalytic decomposition by iron(III) salts without acrylonitrile present. The amount of hydrogen peroxide decompsed on the average is more than two molecules per molecule of the formed polymer. The experimental data are briefly discussed in relation to a plausible reaction mechanism.
Nuclear magnetic resonance in polytrifluorochlroethylene
Authors: Nishioka Atsuo
Published: April 2003

Nuclear magnetic resonance of F19 in polytrifluorochloroethylene resin was studied from ‐172°C. to +205°C. near the melting point. Line width transitions of this polymer were measured with two kinds of specimens, polymers with NST at 300 and 240. From the changes of line width it appears that band narrowing occurs above ‐30°C., and segmental motion seems to take place at about 70°C. A plot of correlation time versus temperature shows a change of slope at about 70°C. Two values of the activation energy, 1.6 and 5.2 kcal./mole in the lower and higher temperature ranges, respectively, are obtained; these seem to be attributable to small‐scale intrasegmental motions and large scale main segmental motions below and above the second‐order transition range, respectively. The line width appears much broader in the lower molecular weight speciman (NST 240). This may be due to the higher degree of crystallization in the lower molecular weight crystalline polymer. The second moment for the rigid state was for the model calculated as 8.0 and 6.9 gauss2, respectively, by making some crude assumptions in both the cases of isotactic and syndiotactic arrangements as compared with the observed value, 7.7 gauss2 at ‐172°C.
Infrared spectrum of polyvinylidene chloride. II
Authors: Narita S. , Ichinohe S. , Enomoto S.
Published: April 2003

In order to complete the more advanced assignments of the bands in the spectrum of polyvinylidene chloride, we prepared deuterated polyvinylidene chloride and obtained its spectrum. With the assumption that frequencies of the skeletal stretching modes and the CCl2‐stretching modes cannot change drastically by deuteration, we have achieved the following assignments. Since the frequencies of the bands at 516, 527, 565, 580, 600, and 655 cm.−1 did not change largely by deuteration, they are assigned to the CCl2‐stretching modes. We can assign the crystallization sensitive band at 753 cm.−1 to the CH2‐rocking mode, because it was shifted to 607 cm.−1 by deuteration. The other crystallization sensitive band at 884 cm. −1, which was shifted to 822 cm.−1 by deuteration, is assigned to the skeletal stretching mode. From the frequency changes by deuteration, we could conclude that our previously reported assignments of the bands at 1046, 1071, 1357, 1407, 2966, and 3010 cm. −1 are reasonable.
Infrared spectra of crystalline polysaccharides. I. Hydrogen bonds in native celluloses
Authors: Liang C. Y. , Marchessault R. H.
Published: April 2003

The infrared spectra of oriented films of valonia cellulose and of ramie and bacterial cellulose crystallites have been observed in the 3 μ region. Polarization properties of the bands have also been determined. The differences between the polarized spectra of bacterial and ramie crystallites in this region are attributed to per cent crystallinity and orientation effects. Two new bands in the CH stretching region have been observed. With this new information the CH2 symmetric and antlisymmetric stretching modes are assigned to parallel and perpendicular bands, respectively, requiring a specific orientation of the CH2OH group. From the observed polarization of the bands in the OH stretching region, a system of hydrogen bonding in the crystal structure of cellulose I is proposed. This involves a change in conformation of the cellobiose unit to permit an intramolecular hydrogen bond between the C3 hydroxyl and the ring oxygen of contiguous glucose units. Two sets of intermolecular hydrogen bonds are proposed: in the 101 plane the C6 hydroxyls of the antiparallel chains are joined to the bridge oxygens of the adjacent parallel chains; in the 101 plane the C6 hydroxyls of the parallel chains are hydrogen‐bonded to the bridge oxygens of the adjacent antiparallel chains.
The pyrolysis of dimethylpolysitloxanes. II
Authors: Lewis Charles W.
Published: April 2003

Under conditions of vacuum pyrolysis, the rate of weight loss of dimethylpolysiloxanes varies from one sample to the next in an apparently random fashion. This variation is attributed to catalyzed chain cleavage brought about by trace impurities.
The polymerization of diallyl phthalate, an investigation by infrared spectroscopy
Authors: Spurr Robert A. , Hanking Betty M. , Rowen John W.
Published: April 2003

The changes in relative unsaturation of the monomer‐polymer system of diallyl phthalate have been studied by means of the infrared absorption hand at 1645 cm.‐1 over the temperature range of 60‐120° both before and after gelation. It was found that the initial reaction can be described in terms of second‐order kineties with an activation energy of 15,900 cal./mole. Relationships have been derived for (a) the dependence of the relative unsaturation u/u0 on the degree of conversion α, and (b) the relationship among α, time, temperature, and catalyst concentration. The value of α at the critical point determined in the above manner is in good agreement with the theory but appears to he temperature‐dependent; possible reasons for this dependency are given. It is pointed out that the infrared technique is a suitable method for study of post‐gelation kinetics and polymer structure.
Kinetics of polymerization of N‐vinylurethane
Authors: Ghosez L. , Smets G.
Published: April 2003

The kinetics of polymerization of N‐vinylurethane has heen studied hy rate determination as well as by determination of molecular weights. The order of reaction with respect to the initiator (azoisobutyronitrile) is equal to 0.5 both in bulk and in acetone solution (2.95 moles/1.); moreover, any thermal polymerization is negligible under these experimental conditions. The number‐average molecular weights of the polymers were determined by the osmotic method; the chain transfer with monomer at 60°C. is equal to 2.5 × 10‐5. It can be shown that the efficiency of the initiator is at least equal to 0.59, and that the chain termination proceeds principally through disproportionation. The ratio kp2/kt is about 0.18, which is practically equivalent to that of vinyl acetate. By polymerization in solution and by determination of the corresponding molecular weight, chain transfer constants at 60°C. were evaluated for acetone (Cs = 8.5 × 10‐4) and for benzene (Cs = 1.25 × 10‐4); these values were confirmed by rate measurements. The rate dependence on monomer concentration is different in each case. In dilute solution, the order is 1 in benzene, while it is nearly 1.5 in acetone. In concentrated solutions, the apparent order increases gradually, owing to the importance of both chain transfer and cross‐termination reactions.
Kinetics of polymerization of vinyl benzoate
Authors: Banerjee S. , Muthana M. S.
Published: April 2003

Vinyl benzoate was polymerized in bulk as well as in solution, using benzoyl peroxide and azobisisobutyronitrile initiator at a temperature of 79.6°C. The overall rate of polymerization was found to be proportional to the concentration of the monomer and to the square root of the initiator concentration. Polymerization progressed to a normal extent, except that it increased with conversion, probably because of transfer with polymer. The value of the transfer constants with the monomer, initiator, and some solvents are reported.
Degradation of long chain molecules by ultrasonic waves. VIII. Rate constants and the cavitation process
Authors: Jellinek H. H. G.
Published: April 2003

Solvent velocities at a constant distance from the center of a collapsing cavity have been calculated for a liquid exposed to ultrasonic waves. These velocities can be expressed as a function of time by a sine function. This permits the calculation of degradation rate constants as a function of polymer chain length, intensity, and frequency of the ultrasonic waves and also as a function of the hydrostatic pressure exerted on the reaction system. In all cases, the calculated rate constants show relationships similar to those found for experimental rate constants. In some cases (e.g., initial chain length) quite a good quantitative agreement is obtained.
Composition and structure effects in alfin catalysts made from some cycloalkenes
Authors: Morton Avery A. , Finnegan Richard A.
Published: April 2003

The product from the metalation of methylcyclohexene can be used in an alfin catalyst combination provided the proportions of the components are suitable, but the sodium compound from the metalation of cyclohexene cannot be used irrespective of the proportions. The metalation product from methylcyclopentene appears to form an alfin catalyst, but that from cyclopentene does not. These facts have an important bearing upon any opinion about the structure of the catalyst and the nature of a surface which affect profoundly the polymerization of butadiene, indeed, control polymer growth.
Kinetics of crystallization of isotactic polypropylene between 120 and 160°C.
Authors: Marker Leon , Hay Peter M. , Tilley George P. , Early Robert M. , Sweeting Orville J.
Published: April 2003

Physical changes which accompany the crystallization of isotactic polypropylenes have been observed by dilatometry and optical microscopy at temperatures between 120 and 160°C. Samples were fused at 220°C. and then held at a predetermined crystallization temperature for times ranging up to many hours. Rate constants for the crystallization were calculated from volume changes and from measurements of radial growth of spherulites. Polypropylenes from different sources exhibited quite different concentrations of spherulites and growth rates. Crystallization appears to proceed, at least at the higher temperatures, by spherical growth from a fixed number of nuclei, apparently arising from foreign matter in the polymer. With decreasing temperature, the number of nuclei (hence also the number of spherulites) increases, since apparently the conditions for nucleation become less critical. The crystallization follows the kinetics of a nucleation‐controlled process according to an Avrami equation, ‐log (1 ‐ ΔV / ΔV ∞) = kt3. Deviations from the third power of time at the lower temperatures may be the result of a secondary ordering process, slower than the primary crystallization.
Polymerization of vinyl bromide in solution
Authors: Blauer G. , Shenblat M. , Katchalsky A.
Published: April 2003

The polymerization of vinyl bromide in 1,2‐dibromoethane solution has been investigated using 2,2′‐azobisisobutyronitrile as thermal initiator. Rates of polymerization were followed in high vacuum by dilatometric and gravimetric measurements. Under the conditions employed, the polymerization showed no acceleration of rate. Up to about 12 hours reaction there was no significant loss of bromine from the polymer. At 35°C. and in the monomer concentration range 1–5 M, the initial rate was dependent on a power close to 2 of the monomer concentration. The rate at 35°C. was also dependent on a power close to 1.0 of the initiator concentration in the range 0.01–0.1 M. Styrene yielded an exponent 0.5 for the initiator at analogous experimental conditions. The average molecular weight of the initial polymers prepared under the conditions and in the concentration ranges indicated above were determined by light scattering and viscometry. The molecular weights were of the order of 100,000 and did not depend significantly on the initiator concentration. The intrinsic viscosities increased by only 50% when the monomer concentration was increased threefold and showed even less variation when the reaction temperature was lowered to 20°C. It is suggested that the polymerization system, though in apparent homogeneous solution, is close to phaseseparation, and beyond a critical range of degree of polymerization the highly coiled macromolecular radicals are unable to terminate by bimolecular collision, while at still higher degrees, even propagation inside the buried radicals ceases. This mechanism is supported by temperature dependent reversible association phenomena found previously. Alternative explanations based on chain transfer reactions involving unreactive radicals are discussed.
Nitrogen‐containing monomers. I. Copolymerization reactions of N‐alkyl maleamic acids and N‐alkyl maleimides
Authors: Coleman L. E. , Conrady J. A.
Published: April 2003

The polymerization reactions of some N‐alkyl maleamic acids and N‐alkyl maleimides have been described and a number of copolymers have been characterized. The N‐alkyl maleamic acids do not homopolymerize under the conditions employed but do copolymerize with styrene, acrylonitrile, and methacrylates. N‐Alkyl maleimides form homopolymers readily and copolymerize with a variety of vinyl monomers. Reactivity ratios of N‐butyl maleimide with styrene and methyl methacrylate have been determined, and Q and e values have been calculated.
The spreading of liquids on polyethylene film. The effect of preprinting treatments
Authors: Allan A. J. G.
Published: April 2003

A study has been made of the wettability of thin films of polyethylene by observing the equilibrium advancing contact angle formed by a drop of liquid on the surface. Treatment of polyethylene film by exposure to methane/oxygen flames of varying intensity produces a controllable increase in the polarity of the surface as measured by the contact angles with a series of solutions of ethyl alcohol in water. The surface tension lowering of water by ethyl alcohol required to give complete spreading was determined for each flaming condition and related to the adhesion of a polar printing ink. It is shown that an essential criterion for good ink adhesion is the complete wetting of the film surface by the ink. It is suggested that a simple measure of the efficacy of the preprinting treatment would be the contact angle of water with the film.
The effect of the alkyl group on the irradiation grafting of methyl methacrylate to poly(alkyl methacrylates)
Authors: Graham Roger K. , Gluckman Muriel S. , Kampf Mary J.
Published: April 2003

Gamma irradiation of methyl methacrylate monomer in the presence of crosslinked poly(methyl methacrylate) leads to essentially no incorporation of new polymer into the insoluble network. Irradiation of solutions of poly(alkyl methacrylates) in methyl methacrylate produces graft copolymers in relatively low efficiency when the alkyl group is butyl, lauryl, stearyl, isopropyl, 2‐ethylhexyl, cyclohexyl, or neopentyl, but little grafting is observed when the alkyl group is tert‐butyl. It is concluded that prediction of grafting efficiencies cannot be made from the relative energy requirements for polymerization of monomer and cleavage of main‐chain carbon‐carbon bonds in the polymer. Evidence for grafting of alkyl methacrylates to poly(alkyl acrylates) is also presented.
Polymerization of triallyl cyanurate‐polyester resins
Authors: German Dale E. , Clampitt Bert H. , Galli Joseph R.
Published: April 2003

Differential thermal analysis data and infrared spectra are utilized to establish the mechanism by which a particular triallyl cyanurate‐polyester (Vibrin 135) resin polymerizes. It is shown that approximately one‐fourth of the polyester double bonds are of the furnarate type and that only these are capable of homopolymerization. In Vibrin 135, however, all of the polyester double bonds polymerize, along with two of the triallyl cyanurate double bonds, giving rise to one exothermic peak. From the nature of this polymerization it is inferred that a substantial amount of copolymerization occurs. Polymerization of the final triallyl cyanurate double bond, along with isomerization to the polymerized triallyl isocyanurate form, gives rise to a second exothermic peak. Correlation of measured heats of polymerization and infrared data tends to substantiate the proposed mechanism.
Linear phenol‐formaldehyde polymers: Synthesis of ortho‐para linked polymers
Authors: Burke W. J. , Ruetman S. H. , Higginbottom H. P.
Published: April 2003

Linear ortho‐para linked phenol‐formaldehyde polymers were prepared by the addition of tetrahydrofuran solutions of o‐chlorophenol‐formaldehyde polymers to liquid ammonia containing sodium. The resulting phenol‐formaldehyde polymers were crosslinked much more slowly by reaction with hexamethylenetetramine than were the isomeric ortho‐ortho linked phenol‐formaldehyde polymers. Infrared and acetylation studies were consistent with proposed structure.
cis‐trans Isomerization in polyisoprenes. Part III. Reduction in the rate of crystallization of natural rubber at low temperatures by treatment with sulfur dioxide
Authors: Cunneen J. I. , Watson W. F.
Published: April 2003

The explanation given previously for the low rates of crystallization of natural rubber at moderately low temperatures after treatment by thiol acids leads to the prediction that treatment of rubber with sulfur dioxide above the ceiling temperature will give modified rubbers of low crystallization rates. This prediction is confirmed. Butadiene sulfone addition to rubber and heating to a convenient rate of its decomposition also gives rubber of low rate of crystallization. The cis‐trans mechanism of reaction is briefly discussed.
Wettability of perfluorocarbon polymer films: Effect of roughness
Authors: Allan A. J. G. , Roberts R.
Published: April 2003

The wettability of various perfluorocarbon polymer surfaces has been studied by observing the advancing and receding contact angles formed by a drop of liquid on the surface. Differences in hysteresis can be given a reasonable interpretation in terms of surface topography. The variation in roughness changes the advancing contact angle by as much as 30° and the advancing‐receding hysteresis varies from 13–59°. It is suggested that the receding angle is probably the more important in adhesion of ice where drops are blown across the surface at glancing angles and, therefore, exceedingly smooth perfluorocarbon polymer surfaces may be better than rougher surfaces for this application. No significant difference was observed between the two polymer structures, polytetrafluoroethylene and the copolymer of tetrafluoroethylene and hexafluoropropylene.
Electron exchange polymers. XI. Oxidation potentials and spectra of water‐soluble hydroquinones and polymeric hydroquinones
Authors: Robinson Ian D. , Fernandez‐Rofojo M. , Cassidy Harold G.
Published: April 2003

Reproducible potentiometric titrations of water soluble electron exchange polymers have been obtained. Sulfonated polyvinylhydroquinone homopolymers and a sulfonated copolymer of vinylhydroquinone with α‐methylstyrene were prepared by treatment of the corresponding dibenzoates with concentrated sulfuric acid. Oxidative titrations with ceric sulfate and bromine water are described. It was found that the apparent standard oxidation potential depends on the degree of reduction and is independent of molecular weight, for large molecular weight. These experimental facts are in agreement with a recent theoretical analysis. The standard oxidation (midpoint) potentials of the polymers are somewhat higher than similarly treated isopropylhydroquinone dibenzoate, model monomer. Some effects of salt and pH on the polymer titration behavior are described. Although the polymer potentials are established slowly on platinum electrodes, ultraviolet absorption studies have shown that the oxidation reaction itself is rapid. A pink‐colored intermediate was observed. The effects of sulfonation of two hydroquinones on their oxidation potentials and ultraviolet absorption spectra are described.
Chain transfer to a mixture of agents: The anomalous behavior of the acrylonitrile–dimethylformamide–water system
Authors: Jenkins A. D. , Johnston R.
Published: April 2003

A method is described for determining the velocity constant for chain transfer in a vinyl polymerization to a relatively weak transfer agent which occupies a significant volume fraction of the reaction mixture. The method is particularly useful for cases in which precipitation of the polymer by the transfer agent would occur in the absence of an additional solvent. Some results for the acrylonitrile–dimethylformamide–water system are given, and the observed anomalous chain transfer behavior is interpreted in terms of the formation of a hydrate of dimethylformamide which is believed to be inert with respect to growing acrylonitrile radicals.
The optical behavior of spherulites in crystalline polymers. Part I. Calculation of theoretical extinction patterns in spherulites with twisting crystalline orientation
Authors: Keith H. D. , Padden F. J.
Published: April 2003

The extinction behavior of spherulites in many polymers and nonpolymers is shown to result from a characteristic twisting of crystal orientation acquired during growth. Extinction patterns are calculated for model spherulites consisting of radial fibers in which uniaxial or biaxial crystalline fibers twist regularly in a right‐ or left‐handed sense about the fiber axis. The results are in good agreement with observed extinction patterns in all of the following cases: diametral sections of three‐dimensional spherulites, diametral sections tilted on a Federow universal stage, and two‐dimensional spherulites grown in thin films. Details of this correlation will be given in Part II. Rules are given for (a) detecting the existence of twisting orientation, (b) determining whether it is of right‐ or left‐handed sense, and (c) determining the crystallographic axis about which twisting occurs.
On extinction patterns of polymer spherulites
Authors: Price Fraser P.
Published: April 2003

The extinction patterns between crossed nicols shown by two types of arrays of uniaxial crystals have been investigated. The arrays were (a) a disk whose radii were twisted arrangements of such crystallites, the plane of the disk being tilted at an arbitrary angle to the direction of observation, and (b) a cone of arbitrary apex angle whose sides were composed of twisted arrangements of crystallites, the cone being observed along the axis. The optic axes of the crystallites make an arbitrary but fixed angle with a radius of the disk or a ray of the cone. The extinction patterns of the disks can be circles, distorted displaced loops or zigzags, or mixtures of these, depending on the parameters. The extinction patterns of the conical arrays can be spirals or zigzags or both.
Kinetics of the Alfin polymerization of styrene and isoprene
Authors: Cleland Robert L. , Letsinger Robert L. , Magat Eugene E. , Stockmayer W. H.
Published: April 2003

The overall rate of polymerization of styrene and isoprene with the heterogeneous allylsodium–sodium isopropoxide–sodium chloride (Alfin PP) system as initiator is reaction‐controlled and is first order with respect to monomer and proportional to the amount of initiator present. The intrinsic viscosity of the product is independent of the monomer and initiator concentrations. The rate of styrene polymerization is independent of alkoxide concentration over a certain range, while the intrinsic viscosity increases with increasing alkoxide concentration. The activation energy of the overall rate is about 12 kcal./mole for styrene and 10 kcal./mole for isoprene. The simplest explanation of the kinetic results assumes initiation and termination steps involving the monomer. The distribution of molecular weights in Alfin polystyrene appears very broad. The kinetic features of this reaction bear a strong resemblance to those of the formation of isotactic polymers from the alkyl aluminum–titanium chloride system (Ziegler catalyst.)
Infrared spectra of crystalline polysaccharides. II. Native celluloses in the region from 640 to 1700 cm.−1
Authors: Liang C. Y. , Marchessault R. H.
Published: April 2003

The infrared spectrum of uniplanarly oriented valonia cellulose film and the polarized infrared spectra of doubly oriented films of ramie and bacterial cellulose crystallites have been observed in the region from 640 to 1700 cm.−1. The spectra have been interpreted with the assistance of band assignments in cellulose derivatives and related small molecules. Data obtained from deuterated material, band polarizations, and tilting effects have also been used. The perpendicular band at 1317 cm.−1 is assigned to the CH2 wagging mode. The highly parallel polarized band at 1162 cm.−1 is assigned to the antisymmetric bridge COC stretching frequency and the slightly parallel polarized band at 1110 cm.−1 is assigned to a ring stretching frequency. The interpretations of the other observed bands are discussed generally.
The polymerization of acrylonitrile in aqueous solution. Part I. The reaction catalyzed by Fenton's reagent at 25°C.
Authors: Dainton F. S. , Seaman P. H.
Published: April 2003

An apparatus is described for following dilatometrically the polymerization of acrylonitrile in aqueous solution initiated by ferrous salts and hydrogen peroxide. A steady rate (Rp) is rapidly established which ultimately decreases rapidly but does not fall to zero after the initiator is consumed. From measurements of the concentration of the ferrous ion surviving the reaction, the effect of cupric, fluoride, and ferric ions on this, on Rp, on the final phases of this reaction, and on the corresponding reaction with methyl methacrylate, it is concluded that polyacrylonitrile radicals are oxidatively terminated by cupric and ferric ions, but polymethyl methacrylate radicals are not. When this linear termination is suppressed, Rp is proportional to [m1]2 at low monomer concentrations and linearly dependent on [m1] at high concentrations. The transition from one state of affairs to the other occurs at a monomer concentration which first decreases and then increases as the initiation rate (Ri) increases. These results are believed to be general for all modes of initiation and include all previous data, reconciling conflicting information. A qualitative interpretation of these results is given in terms of the fairly rapid attainment of a constant number of polymer particles on which monomer is weakly adsorbed, a proportion of which are at any given moment inert, the remainder growing by consuming adsorbed monomer. Initiation, propagation, and mutual termination in the aqueous phase all play a significant part.