bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal structures in polyamides made from ω‐amino acids
Authors: Slichter W. P. 
Published: April 2003

AbstractThe 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

AbstractA 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

AbstractContinuous 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

AbstractThe 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

AbstractThe 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

AbstractAccording 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

AbstractInvestigations 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

AbstractThe 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

AbstractTheoretical 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

AbstractThe 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

AbstractAn 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

AbstractIt 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

AbstractNuclear 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

AbstractIn 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

AbstractThe 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 polymerization of diallyl phthalate, an investigation by infrared spectroscopy
Authors: Spurr Robert A. , Hanking Betty M. , Rowen John W. 
Published: April 2003

AbstractThe 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

AbstractThe 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

AbstractVinyl 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

AbstractSolvent 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

AbstractThe 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.