bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of physical state during the electron irradiation of hydrocarbon polymers. Part II. Additional experiments and discussion pertaining to trapped radicals in hydrocarbon polymers
Authors: Lawton Elliott J. , Powell R. S. , Balwit J. S. 
Published: April 2003

AbstractThe previous paper discusses the effect of physical state during the irradiation on the fate of the polymer radicals produced. Additional experiments relating to trapped radicals in hydrocarbon polymers are discussed. Three different methods of detection were used; namely, infrared absorption at 5.8 μ, electron paramagnetic resonance, and gasuptake by the irradiated polymer. Conditions for producing trapped radicals at room temperature are that the polymer exist in the crystalline, glassy, or highly crosslinked form during irradiation. Radicals trapped in the crystalline or glassy areas can dissipate either as the result of heating the polymer above Tm or Tg or else by exposure to a radical scavenger, e.g., oxygen or ethylene. The lifetime of radicals trapped in Marlex‐50 can be many thousands of hours at room temperature. Radical decay will take place even with storage in vacuum if given enough time. The decay is arrested by holding the sample at liquid nitrogen temperature. Loss in radical activity in Marlex‐50 when stored in vacuum is due mainly to delayed crosslinking. Trans‐vinylene and vinyl do not appear to enter into the reaction responsible for the decay. A comparison of the decay of radicals trapped in unbranched Marlex‐50 with that in a branched low‐density polyethylene when stored in ethylene, oxygen, and vacuum was made. The results suggest that although radicals are trapped in the crystalline regions of both polymers, there are differences between the two crystals—the crystals in the low‐density polymer do not appear to be as tight as those in the Marlex‐50. Delayed oxidation reactions occurring in the crystalline regions of irradiated Marlex‐50 when stored in oxygen at room temperature require a number of intermediate steps before appearing as carbonyl. An average of 5 molecules of oxygen per polymer radical was used in forming carbonyl. Delayed main chain scissions occur during this process which cause severe embrittlement and loss in physical properties. Significant improvements in physical properties of Marlex‐50 can be achieved through irradiation, but radicals must not be left trapped in the polymer.
Crystalline modifications of cellulose. Part II. A study with plane‐polarized infrared radiation
Authors: Mann J. , Marrinan H. J. 
Published: April 2003

AbstractThe bands due to stretching of OH groups in celluloses I, II and IIII have been studied with plane polarized infrared radiation. The spectra show that all three crystalline modifications contain OH groups which make an angle much smaller than 55° with the chain direction, while other OH groups make angles greater than 55° with this direction. The former OH groups are attributed to intramolecular hydrogen bonds which join successive glucose residues in the cellulose chain. It is shown that ether oxygen atoms must participate in the hydrogen‐bonding systems in all three modifications. The symmetries of the cellulose chains and the relationship between the two chains in the unit cell are discussed in relation to the number of distinguishable OH groups. Structures are described which are in agreement with the infrared results and with the stereochemical considerations presented in Part III of this series. The frequencies of the bands due to intramolecular hydrogen bonds suggest that the chains in cellulose I have a different molecular form from those in celluloses II and IIII. This difference may not be very large, however, in relation to the accuracy with which polymer structures are normally determined.
Freezing point depression of polymer solutions and gels
Authors: Kawai Tōru 
Published: April 2003

AbstractThe freezing point depression of polymer solutions was measured in the concentration range 5% to 30% (by volume of polymer), particular attention being paid to avoid excess supercooling. The polymer‐solvent combinations investigated were polystyrene‐benzene, polyvinyl acetate‐benzene, cellulose acetate‐acetic acid, and polyvinyl alcohol‐water. Through the proper adjustment of the rate of cooling, the freezing curves showed a sharp break, from which the freezing points were determined as a function of polymer concentration with sufficient accuracy to permit discussions of the thermodynamic properties of these polymer solutions. The discussion of these data was made in terms of the interaction parameter, μ, well known in the theory of polymer solutions. The new feature brought out in this work is the marked change of μ with polymer concentration. For all the polymer‐solvent systems studied, fairly rapid fall in μ was observed with increasing concentration. Such behavior in μ is important because it is in no way specific to these systems and leads to the expectation that, for polymer solutions in general, μ (or, at least μs, the entropy contribution to μ) should fall progressively as the polymer concentration is increased, with a corresponding increase in the degree of overlapping of the excluded volumes of polymer molecules. The earlier theories of polymer solutions require improvement in this direction. In the cases of the systems, cellulose acetate‐acetic acid and polyvinyl alcohol‐water, the orientation and strong heat of mixing effects must also be considered because of the polar nature of the components. In order to carry out further quantitative discussion on the results obtained, we must wait until more complete theories of polymer solutions will be developed. It has become apparent, nevertheless, that the freezing point determination furnishes our best source of information concerning the thermodynamic properties of polymer solutions. As for aqueous solutions of polyvinyl alcohol, possible effects of the intermolecular junction points which might be produced in the solution on cooling upon the results were examined, but negative results were obtained. Finally, a possibility was suggested for development of this method to permit extensions to lower and higher concentration ranges than those covered by the present work, the latter (higher concentration range) including gels produced by polymer networks and assemblages of moist fibers.
A theoretical study on the mechanism of Ziegler‐type polymerizations
Authors: Uelzmann Heinz 
Published: April 2003

AbstractThe polymerization of olefins with Ziegler catalysts is an intercomplex ion polymerization taking place on two metal atoms. A cationic initiation occurs on a cation of a transition element. In the case of a stereospecific polymerization the activated monomer orients toward and inside a negative complex ion (for instance of aluminum) into which it migrates by adding a propagation starter (R−, H−). In this complex anion all further cationically activated monomers propagate anionically until termination occurs by H− abstraction.
Cyclopolymerization. I. Polydiacrylylmethane
Authors: Jones J. F. 
Published: April 2003

AbstractThe attempted synthesis of diacrylylmethane by the acylation of methyl vinyl ketone with ethyl acrylate produced exclusively the homopolymer of diacrylylmethane. This new polymer is linear and is composed of recurring methylene dihydroresorcinol units. An anionic mechanism is proposed for the cyclopolymerization of diacrylylmethane. Polydiacrylylmethane undergoes chemical reactions which are characteristic of beta diketones and proof for structure of the polymer is based on solubility, fusibility, infrared absorption, ultraviolet absorption, and enol titration data.
Cyclopolymerization. II. Polyacrylic anhydride
Authors: Jones J. F. 
Published: April 2003

AbstractA linear high polymer composed of repeating α‐methylene glutaric anhydride units has resulted from the controlled cyclopolymerization of acrylic anhydride. Proof for the linear nature of this polymer is based upon solubility and thermoplastic behavior. Proof for the cyclic nature of the polymer is based upon the lack of residual unsaturation. The molecular weight of linear polyacrylic anhydride has been altered by the use of chemical modifying agents in the polymerization recipe. Linear polyacrylic anhydride undergoes characteristic carboxylic anhydride reactions.
Static electricity in polymers. I. Theory and measurement
Authors: Shashoua Victor E. 
Published: April 2003

AbstractA versatile instrument, The Static Propensity Tester, was constructed for the measurement of the rate of electrostatic charge build up and decay on polymer films and fabrics. The tester was used for measuring the rates of both positive and negative potentials in the voltage range of 1000–10,000 volts. From such studies it was observed that above a certain minimum potential, it always took longer for charge to build up on a sample than to decay. Also, the rate of charge decay was found to be dependent on the exposed surface area of a sample as well as its electrical resistance. The loss of charge from a given substance was postulated to occur by two processes, a conduction process through the substrate and a radiation process through the atmosphere. In addition, polymers were found to exhibit a charge selectivity for the sign of the applied voltage, i.e., wool had a faster negative charge decay rate whereas cellulose had a faster positive decay rate. The root‐mean‐square half life of charge decay for positive and negative voltages was found to follow an exponential type law with respect to magnitude of charge and relative humidity. A simple test was devised for characterizing the antistatic behavior of polymers.
The copolymerization characteristics of ethyl α‐acetoxyacrylate
Authors: Unruh C. C. , Laakso T. M. 
Published: April 2003

AbstractThe copolymerization characteristics of ethyl α‐acetoxyacrylate with four different monomers have been investigated, and the reactivity ratios r1 and r2 determined in the case of each comonomer pair. The monomers used were styrene, methyl methacrylate, vinyl acetate, and ethyl acrylate. From these data were calculated the Q and e values for ethyl α‐acetoxyacrylate. It is apparent that this monomer resembles ethyl acrylate very closely in its copolymerization characteristics.
Molecular weight–viscosity relationship of gamma‐irradiated octadecyl vinyl ether and octadecyl methacrylate
Authors: Fee Jeanne G. , Port William S. , Witnauer Lee P. 
Published: April 2003

AbstractOctadecyl vinyl ether and octadecyl methacrylate monomer were polymerized by means of gamma radiation from a cobalt‐60 source. The weight‐average molecular weight and the intrinsic viscosity of the resulting polymers were determined. The constants K′ and a were 0.25 × 10−4 and 0.75, respectively, for poly(octadecyl methacrlylate) and 22.4 × 10−4 and 0.35, respectively, for poly(octadecyl vinyl other).
Dynamic mechanical properties of irradiated polyethylene
Authors: Butta E. , Charlesby A. 
Published: April 2003

AbstractDynamic mechanical properties of eight samples of polyethylene irradiated to various extents have been determined over a temperature range from −70 to +280°C. and a frequency range from 103 to 2 × 104 cycles/sec. At room temperature, minimum values in Young's modulus and maximum values in damping factor are observed for a critical radiation dose. Three transition points Tg, Ts, and Tm are exhibited by the sound velocity‐temperature curves; these may be associated with the transition from the glass state, the softening of the amorphous regions, and the melting of the crystallites, respectively. With increasing dose, Tm, decreases and Tg, increases, while Ts shows a minimum for a radiation dose equal to the critical value. At temperature above the melting point of the crystallites Tm, lightly crosslinked samples show rubber‐like elasticity, but highly crosslinked samples show the same dynamic mechanical behavior as highly crosslinked amorphous materials. Results are discussed and explained on the basis of the partial crystallinity of polyethylene and of the changes that irradiation causes on the molecular structure.
Infrared spectroscopy of polyethylene terephthalate
Authors: Daniels W. W. , Kitson R. E. 
Published: April 2003

AbstractThe absorption spectra of polyethylene terephthalate, polyethylene‐D4 terephthalate and polyethylene terephthalate‐D4 were investigated. From these spectra and those of other known compounds, assignments were made for most of the bands in the 2 to 15 micron region. The 13.7 μ band was shown to be due to the out‐of‐plane bending of the aromatic hydrogen. The bands in this region known to vary in intensity with crystalline/amorphous ratio of the polymer were shown to be present in the spectrum of ethylene dibenzoate and to behave in an analogous manner with changes of state. From a study of this model compound and other considerations, rotational isomerism was postulated as the origin of the variation in intensity of these bands. Carboxyl and hydroxyl endgroup bands were identified and used to determine polymer number‐average molecular weight in good agreement with values obtained by osmotic pressure methods. A band arising from ether linkages (which are formed via dehydration during polymer synthesis) was identified.
Thermal degradation of polymethacrylonitrile. IV. Formation and decomposition of ketene‐imine structures
Authors: Grassie N. , McNeill I. C. 
Published: April 2003

AbstractThe reaction of ketene‐imine structures in polymethacrylonitrile is most conveniently followed by observing the disappearance of the 2012 cm.−1 peak in the infrared spectrum. These structures are stable to 120°C. in the bulk material but disappear rapidly in solution at lower temperatures. Like simple ketene‐imines they are destroyed by addition of water, chlorine, methanol, and hydrogen sulfide. Thermal decomposition in cyclohexanone solution in the temperature range 65–90°C. is a second‐order process. The second‐order rate constant decreases with increasing polymer concentration although, within experimental error, it is independent of the ketene‐imine concentration. The rate constant can also be depressed by addition of polymethyl methacrylate. These observations have been interpreted in terms of diffusion (viscosity) control of the reaction rate. Ketene‐imine structures are formed during polymerization by reaction of the growing polymer radical in the form
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By preparing a series of polymers at the same temperature (30°C.) but with different initiator concentrations and determining their ketene‐imine contents, it has been possible to show that the ketene‐imine structures are formed predominantly in the termination step. The ketene‐imine form of the radical appears not to be reactive enough to add monomer readily in a propagation process. The mechanism of the thermal disappearance of ketene‐imine structures is not clear. In particular it is difficult to correlate the second‐order kinetics with the chain‐scission process which is associated with the reaction. There is some evidence, however, that the extent of this chain scission is a measure of ketene‐imine concentration.
The degradation of polymer molecules in solution under the influence of ultrasonic waves. Part I. Kinetic analysis
Authors: Ovenall D. W. , Hastings G. W. , Allen P. E. M. 
Published: April 2003

AbstractStarting from the assumption that a polymer molecule in solution will only degrade under the influence of ultrasonic irradiation if both the resulting fragments are greater than Pe/2 in size, where Pe is the so‐called limiting degree of polymerization, rela tionships are derived giving the rate of degradation in terms of rate of breaking of bonds. If dBi/dt the rate of breakage of bonds in molecules of size Pi, the proposed rate equations are: dBi/dt = k(Pi – Pe)ni for Pi > Pe and dBi/dt = 0 for Pi ⪕ Pe, where k is a constant characteristic of the system and ni is the number of molecules of size Pi. Solutions of this equation are given for three sets of conditions.
A theory for the high field conductance of polyelectrolytes
Authors: Wissbrun Kurt F. , Patterson Andrew 
Published: April 2003

AbstractUsing a theory based on that of Onsager for the dissociation field effect, the authors have shown it is possible to explain the dependence of the Wien effect or polyelectrolyte samples on concentration, molecular weight, and gegenion mobility. The theory has been used to calculate a parameter, q, interpreted as representing a function of polyion size. It has been shown that for samples of polystyrenesulfonic acid the variation of q with increasing neutralization showed a constant polyion size, as would be expected of a fully charged polyion when only the gegenions are exchanged; a sample at a smaller concentration had a larger polyion, as would be expected. For samples of polyacrylic acid, the variation of q with increasing neutralization was initially similar to that revealed by viscosity or light scattering measurements—a rapid increase in polyion size. In our measurements, however, the size remained relatively constant over a considerable range of neutralization and then decreased slightly. This is interpreted as meaning that the ions removed from the polyion are those near the surface, and that the radius of importance in this particular experiment is more nearly the radius of the extended polyion cylinder and not a radius computed from the end‐to‐end separation of the polyion.
The dissolution of water‐insoluble polymers in the surfactant solution. The polyelectrolyte‐like behavior of the dissolved polymers
Authors: Isemura Toshizo , Imanishi Akira 
Published: April 2003

AbstractPolymers, such as polyvinyl formal (PVF) and polyvinyl acetate (PVAc), which are insoluble in water, dissolved in anionic surfactant solution. Polymer solutions of PVF, PVAc, and polyvinyl alcohol in surfactant were studied viscometrically and electrophoretically. The polymer forms a complex with the surfactant, the behavior of which is similar to that of polyelectrolyte. The complex is negatively charged and migrates to the anode. With dialysis of the solution of polymer‐surfactant complex against running water, the polymer separates out; however, the polymer does not separate out of undialyzed solution, even if the solution is diluted to far less concentration than the CMC of the surfactant. Thus the dissolution of the polymers in the surfactant solution is due to the oriented adsorption of surfactant ions on the polymer molecule. The amount of adsorbed surfactant ions was estimated. The adsorption might be of the Langumuir type.
Copolymers of acrylic acid and N‐vinylpyrrolidone‐2
Authors: Uelzmann Heinz 
Published: April 2003

AbstractAcrylic acid and N‐vinylpyrrolidone‐2 copolymerize readily in tetrahydrofuran. High yields of copolymers are obtained if not more than 3 moles of N‐vinylpyrrolidone‐2 are used per mole acrylic acid.
On the mechanism of polymerization retardation by aromatic nitro compounds
Authors: Ihrig Judson L. , Wong Rose K. L. 
Published: April 2003

AbstractIn vinyl polymerization retarded by aromatic nitro compounds, the growing chain reacts with the retarder to form stabilized products. The locus of radical attack has been reported as taking place at an aromatic carbon or at a nitro‐group oxygen. A direct experimental test has been devised to permit a choice between these alternatives. Rates of racemization of optically active nitrobiphenyl derivatives used as retarders in polymerizing systems have been compared with rates in nonpolymerizing monomer. These compounds were found to racemize more rapidly in the presence of polymerizing methyl methacrylate or vinyl acetate. Benzoyl peroxide initiator was not responsible for the considerable difference in racemization rate. The results support the view that primary attack of the growing chain is upon the nitro group and not at an aromatic carbon atom.
Electron spin resonance studies of radicals trapped in polymers
Authors: Atherton N. M. , Melville Harry , Whiffen D. H. 
Published: April 2003

AbstractElelctron spin resonance measurements have been used to follow radical concentrations in the copolymerization of methyl methacrylate and glycol dimethacrylate at 23 and 0°C. and the decay of such radicals. The results have been interpreted to give a qualitative picture of the radical trapping process. It has also been shown that the allyl group in allyl methacrylate is comparatively unreactive and does not take much part in either the polymerization of this monomer or its copolymerization with glycol dimethacrylate. Acrylonitrile and α‐methyl acrylonitrile have been shown to give different electron spin resonance spectra illustrating the effect of a chain methyl group. This parallels electron resonance studies of γ‐irradiated acrylates and methacrylates.
The polymerization of acrylonitrile in aqueous solution
Authors: Dainton F. S. , Seaman P. H. , James D. G. L. , Eaton R. S. 
Published: April 2003

AbstractThe kinetics of polymerization of acrylonitrile in aqueous solution when initiated (a) by Fenton's reagent and (b) photochemically using various photosensitizers have been determined dilatometrically over a wide range of conditions. Whenever ferric salts are either present initially or generated in situ, some polyacrylonitrile radicals (S*) are always destroyed by the reaction;

for which k = 6.7 × 10−5 exp { −2.3 kcal./RT} . mole−1 sec.−1. Reaction (1) may be suppressed by addition of fluoride ion. When Fe3+OH− is used as the photosensitizer for 3130 A. light, the intensity exponent x is given by 1 > x > 0.5, being larger the greater [Fe(III)]. This effect is also due to reaction (1) competing with mutual termination, and measurements of d[Fe(II)]/dt confirm this and lead to values of the primary quantum yeild in agreement with published values. The rotating sector technique can be applied and gives kp = 3 × 107 exp { −4.1 kcal./RT} and kt = 3 × 1013 exp { −5.4 kcal./RT} l. mole−1 sec.−1. From observations of the small photo after‐effect, the “build up” to the steady state in both (a) and (b) above, and the effect of mechanical agitation on all these phases of the reaction, it is concluded that some of the observed rate is due to polymerization of radicals buried in polymer particles, P* (one radical per particle) utilizing adsorbed monomer. In mechanically undisturbed systems, P* particles are constant in number throughout the steady state, decay slowly and bimolecularly during the after‐effect, but are not oxidized by Fe(III). The presence of these particles is responsible for the changing order with respect to [m1] from two to unity as [m1] is increased. The value of [m1]c, the concentration at which this changae of order takes place, is dependent on the rate of initiation and air temperature in a way which reconciles previously published conflicting rate equations.