bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of high molecular polyoxamides at a liquid—gas interface
Authors: Sokolov L. B.
Published: April 2003

The principle of the new gas‐phase method of polycondensation consists of carrying out the polycondensation reaction of two high reactive compounds at a liquid—gas interface. The gas‐phase method permits the synthesis of polyamides with rapidly hydrolyzing diacid chlorides (e.g., oxalyl chloride), which cannot be used for liquid—liquid polycondensation. The gas‐phase synthesis of polyhexamethyleneoxamide from hexamethylenediamine and oxalyl chloride has been investigated in detail. The common features of gas‐phase and interfacial methods of polycondensation are due to the fact that in both cases the chemical reaction proceeds in the polymeric film. The gas‐phase methods can be used for the synthesis of a series of polymers.
Changes in the rate of anionic polymerization of octamethylcyclotetrasiloxane caused by the formation of complexes on silanolate active centers
Authors: Kučera Miloslav
Published: April 2003

The effect of bases on the anionic polymerization of octamethylcyclotetrasiloxane (tetramer) initiated by ∼Si—OK groups has been studied. In the presence of hydroxides of alkali metals or of other Lewis bases, in particular of anisole, complexes are formed on active centers which alter the reactivity of the centers. The effects of the presence of NaOH, LiOH, anisole, and excess KOH on the polymerization of tetramer initiated by ∼Si—OK groups have been determined at various temperatures. An explanation is proposed for the retardation effect of LiOH and NaOH on the polymerization of tetramer; the effects of anisole and excess KOH has been discussed. Also the molecular weight of polydimethylsiloxane is affected by the presence of bases. A hypothesis of the formation and decomposition of complexes on active centers has been formulated which can explain the observed changes in the molecular weight of the polymer. The overall energies of activation of tetramer polymerization initiated by KOH in the presence of LiOH, NaOH, excess KOH, and anisole have been measured. Also measured were values of equilibrium constants of reactions of formation and decomposition of complexes of ∼Si—OK groups with LiOH, NaOH, and KO∼Si— and the corresponding heats of reactions.
Stability of polyvinyl chloride in the presence of nitrating acid
Authors: Wolkóber Zoltán
Published: April 2003

Under the effect of sulfuric acid, oil of vitriol, or chlorosulfonic acid, with the simultaneous formation of sulfur dioxide, hydrochloric acid, and carbon dioxide, the polyvinyl chloride is transformed to a reticulated product which is insoluble in organic solvents and usable for ion‐exchange. The rate of reaction is dependent on the specific surface of polyvinyl chloride, the temperature, and the concentration of the sulfuric acid. In the presence of nitric acid, the reactivity of the polyvinyl chloride to the sulfuric acid changes fundamentally. Under duly chosen circumstances, and in the presence of several per cent of nitric acid, the polyvinyl chloride shows no appreciable change in composition in 100% sulfuric acid, even at 175°C., and it retains its thermoplastic properties and its solubility; only its molecular weight is decreased. At higher temperatures the polyvinyl chloride is slowly oxidized by the nitrating acid. On the basis of our investigations on the stabilizing effect of the nitric acid, conclusions can be reached concerning the rates of reactions initiating the decomposition of polyvinyl chloride and the subsequent reaction, the ratio of reaction rates, as well as the kinetics of the processes taking place in sulfonation and dehydrochlorination. The high stability of the polyvinyl chloride to the nitrating acid indicates that the zip reaction starts at one or two points of the individual molecules of polyvinyl chloride, and this reaction runs along the whole macromolecule. The strong stabilizing effect of the nitric acid can be attributed to the fact that it reacts with the double bond formed at the beginning of the decomposition at a higher rate than of the chain reaction of splitting off of hydrochloric acid from the allyl structure.
Struktur der dienpolymeren in zusammenhang mit der natur der katalytischen systemen
Authors: Dolgoplosk B. A. , Erussalimskiǐ B. L. , Kropatsheva E. N. , Tinyakova E. I.
Published: April 2003

Die Struktur der Dienpolymeren ist in Zusammenhang mit der Natur der katalytischen Komplexen studiert worden. Es ist festgestellt worden, dass die Polymerisation der Diene durch den Chromoxydkatalysator zu kristallinen trans‐1,4 Polymeren führt. Polymerisation der Diene unter dem Einfluss von homogenen und heterogenen Systemen, die aus Dialkylaluminimumhalogeniden und verschiedenen Co‐Verbindungen (CoO, Co3O4, CoSO4, Co‐halogeniden, kohlenwasserstofflöslichen Co(CO)4 und Alkohol‐ und Pyridinkomplexen von CoCl2) zusammengesetzt sind, ist studiert worden. Die Struktur von Polybutadien und Polyisopren, die durch alle angeführten Systeme erhalten sind, ist für alle Fälle ziemlich gleich. Besonders aktiv und stereospezifisch wirkt das homogene System aus Dialkylaluminiumhalogenid und Alkohol‐ oder Pyridinkomplex von CoCl2, das eine Bildung von Polybutadien mit 95% von cis‐1,4 Kettenglieder hervorruft. Die Abhängigkeit des Molgewichtes von Polybutadien von der Konzentration des löslichen Pyridinkomplexes von CoCl2 entspricht der Gleichung M = KC1/2. Beim Studium der Zusammenwirkung zwischen Kobaltoxyden oder CoCl2 und AlEt2Cl ergab es sich, dass die Bildung vom katalytischen Komplex ist nicht von redox Reaktionen begleitet. In dem System aus Co(CO)4 und AlEt2Cl geht der Polymerisation das Stadium einer Bildung von unlöslichem katalytischen Komplex voran. Dessen Zusammensetzung ist studiert worden. Die Reaktion zwischen AlEt3 und Kobalthalogeniden ist erforscht; wie gezeigt, sie kann zur Auslösung der Polymerisation ausgenützt werden. Es ist festgestellt worden, dass ätherfreie magnesiumorganische Verbindungen die Polymerisation der Diene auslösen. Besonders einheitlich ist die Struktur von Polyisopren (96–99% 3,4‐Kettenglieder), durch grösste Polymerisationsgeschwindigkeit ist Chloropren ausgezeichnet. Cis‐trans Isomerization von Naturkautschuk durch aluminiumorganische Verbindungen, Titanhalogenide und wasserfreien Chlorwasserstoff ist studiert worden. Der Isomerisationsprozess verläuft bei verhältnismässig niedriger Temperatur und wird von einer Verminderung der Doppelbindungen begleitet.
Polymérisations anioniques: Polymeres ω‐ fonctionnels. Réactions de couplage et de greffage carbanionique
Authors: Finaz G. , Gallot Y. , Parrod J. , Rempp P.
Published: April 2003

La polymérisation de monomères vinyliques par voie anionique en milieu tétrahydrofuranne conduit à des polymères ω‐carbanioniques stables, mais susceptibles de donner des réactions avec diverses substances choisies pour leur électroaffinité. On peut ainsi obtenir à volonté des polymères possédant en bout de chaǐne des fonctions acide, alcool, amine, éthylénique, chlorure d'acide, cétone ou autres semblables. Ces réactions se font généralement avec des rendements élevés. Si on effectue des réactions du měme genre en utilisant des réactifs bifonctionnels et des polymères dicarbanioniques, il se produit une réaction de couplage multilatéral, une polycondensation secondaire pouvant conduire dans certains cas à des masses moléculaires très élevées, ce qui prouve le caractère quasi quantitatif de ces réactions de désactivation. En faisant réagir des polymères monocarbanioniques sur des substances macromoléculaires polyfonctionnelles adéquates, on obtient des polymères greffés, avec des rendements et des taux de greffage variables selon les conditions de la réaction et selon la longueur de la chaine du greffon. Les copolymères greffés ainsi obtenus sont très homogènes en composition et leur polydispersité en masse se ramène essentiellement à celle du polymère‐support de départ.
Condensation polymers from 3,9‐bis(7‐carbomethoxyheptyl)‐2,4,8,10‐tetraoxaspiro[5.5]undecane. I. Poly(ester‐acetals) and a novel method for crosslinking them
Authors: Pryde E. H. , Awl R. A. , Teeter H. M. , Cowan J. C.
Published: April 2003

3,9‐Bis(7‐carbomethoxyheptyl)‐2,4,8,10‐tetraoxaspiro[5.5]‐undecane (the pentaerythritol acetal of methyl azelaaldehydate) in the presence of basic catalysts underwent condensation polymerization with ethylene glycol to give linear polymers, either alone or in conjunction with other dibasic esters. These linear poly(ester‐acetals) were susceptible to crosslinking by p‐toluenesulfonic acid and by various metal oxides and salts, such as zinc oxide, zinc acetate, litharge, and magnesium oxide. The crosslinked polymers were insoluble, infusible, transparent solids which were strongly adherent to glass.
Statistische methoden zur ermittlung der verteilung der molekülgrössen in hochopolymeren polymolekularen systemen aus experimentalergebnissen der fraktionierten fällung. I. Mitteilung: Mathematische grundlangen
Authors: Hosemann R. , Schramek W.
Published: April 2003

Die für die Ermittlung der Verteilung der Makromoleküle in Lösungen hochpolymerer Stoffe wichtigsten statistischen Rechenelemente (Momente Pn, insbesondere mittlerer Polymerisationsgrad P, Standardabweichung ΔP und Polydispersität g) werden definiert und der Unterschied zwischen zahlenmässiger Häufigkeitsverteilung h(P) und Massenstatistik H(P) dargelegt. Mit Hilfe der Gammafunktion Λ wird eine sehr allgemeingültige drei‐parametrige Verteilungsfunktion gegeben:

Sie enthält als Entartungsfälle u.a. die Maxwellstatistik und die für lineare bezw‐verzweigte Polysynthesen multifunktioneller Moleküle benutzten Verteilungsfunktionen von Flory:

und von Schulz:

Ebenso wird für hochpolydisperse Verteilungen die Verteilungsfunktion von Kraemer‐Lansing:

und die graphische Darstellung ihrer Integralkurve in einem Summenwahrscheinlich‐keitsnetz nach Wesslau discutiert. Für alle Verteilungskurven wird der mathematische Zusammenhang zwischen den Funktionsparametern c, n, t, ß, P0 und den statistischen Rechenelementen P und g hergestellt.
Statistische methoden zur ermittlung der verteilung der molekülgrössen in hochpolymeren polymolekularen systemen aus experimentalergebnissen der fraktionierten fällung. III. Mitteilung: Der abbrucheffekt und seine abschätzung
Authors: Hosemann R. , Schramek W.
Published: April 2003

Die Unkenntnis des höchsten in einem hochpolymeren, polymolekularen Gemisch vorkommenden Polymerisationsgrades Pe, die endliche Zahl von Fraktionen ebenso wie die Unkenntnis der Verteilungsfunktionen Hn(P) der einzelnen Fraktionen n bedingen eine Reihe systematischer Fehler bei der Berechnung der Verteilungsfunktion. Diese Fehler sind, wie bereits in der zweiten Mitteilung erwähnt, für das konventionelle Auswertungsverfahren nach summierender Treppenfunktion (Schulz) ganz besonders gross. Sie werden in Analogie zu systematischen Fehlern, die bei der Auswertung, von Röntgendiagrammen auftreten, als “Abbrucheffekt” (termination effect) berechnet und mittels der handlichen Gleichung (10) und (10a) abgeschätzt. Für das Auswertungsverfahren nach Funktionstyp, wird der Abbrucheffekt gleichfalls berechnet. An einem praktischen Beispiel der von Schulz und Dinglinger durchgeführten Fraktionierung eines Polystyrol wird gezeigt, dass die nach den beiden Verfahren erhaltenen Polydispersitäten g beträchtlich voneinander abweichen und dass der Abbrucheffekt bei der Auswertung nach Funktionstyp erheblich kleiner ist als bei der Auswertung nach summierender Treppenfunktion. Diese so unterschiedlichen Resultate liegen interessanterweise aber noch innerhalb der aus dem Abbrucheffekt errechneten Fehler. Dies wird als Beweis für die Richtigkeit der durchgeführten Fehlerabschätzung betrachtet. Dies wird als Beweis für die Richtigkeit der durchgeführten Fehlerabschätzung betrachtet. Das Beispiel lehrt, wie vorsichtig man bei der Beurteilung der nach summierender Treppenfunktion gewonnenen Ergebnisse sein muss. Schliesslich wird die Leistungsfähigkeit der beschriebenen hypothesenfreien Auswertungsemethode an zwei Fraktionierungsmodellen und einer realen Fraktionierung gezeigt. Aus der durchgeführten vollständigen Analyse der beiden vorerwähnten Fraktionierungsmodelle geht hervor, dass die Grösse αn = ΔnP/Pn, die allein von den inneren Eigenschaften der einzelnen Fraktionen abhängt, bis auf wenige Prozente für sämtliche Fraktionen eines Systems als konstant angesehen werden darf.

Da sich der mittlere Wert ihres Quadrates leicht abschätzen lässt, erhält man schliesslich eine für die praktische Anwendung wichtige und einfache Gleichung. Auf diese Weise gewinnt man die Kenngrössen P und g des untersuchten polymolekularen Systems in folgender Form:

und

von denen die letztere ausser der Grösse α nur noch die allein aus den 2k direkten Informationen des Fraktionierungsexperimentes (mn und Pn) abgeleitete Grösse ga enthält.
Preparation and physical properties of a homologous series of polyformal urethanes
Authors: Schonfeld Edward
Published: April 2003

α‐ω glycols containing two through ten carbon atoms were reacted with paraformaldehyde. Stable polymers were prepared for the glycols having five or more carbon atoms. The polymers have low molecular weights and are bifunctional with respect to hydroxyl. The polyformals were reacted with tolylene diisocyanate and converted into crosslinked urethane elastomers. Physical properties of the elastomers indicated no significant differences among those prepared from polyformals containing a varying number of methylene groups in the starting glycol.
Elastic moduli of oriented polymers. I. The simple helix, polyethylene, polytetrafluoroethylene, and a general formula
Authors: Shimanouchi T. , Asahina M. , Enomoto S.
Published: April 2003

A method of calculating elastic moduli of simple helical polymers on the basis of the Urey‐Bradley force field is presented. The calculated values for polyethylene and polytetrafluoroethylene are 3.4 × 1012 and 1.6 × 1012 dynes/cm.2, respectively. The former value is in agreement with that obtained for the extended normal hydrocarbons and also in fairly good agreement with the experimental value of polyethylene. The general formula for the complex helix is also presented.
Elastic moduli of oriented polymers. III. The (A1A2A3)n and (A1A2A3A4)n types
Authors: Enomoto S. , Asahina M.
Published: April 2003

We have calculated the elastic modulus for polyethylene glycol. It has the magnitude of 4.5 × 1010 − 4.8 × 1010 dyne/cm.2 and it is smaller than the previously calculated values for (A)n and (A1A2)n‐type polymers. The small magnitude is thought to be due to the large changes of the internal rotation angles in polyethylene glycol. The calculation of elastic moduli has been applied to poly‐3,3‐bis(halomethyl)oxacyclobutanes in order to examine the relation between their elastic moduli and van der Waals radii of the halogen atoms.
The mechanism of cellulose biosynthesis by acetobacter acetigenum
Authors: Brown A. M.
Published: April 2003

Measurement of the yield of cellulose in glucose‐containing cultures of Acetobacter acetigenum as a function of inoculum size and growth time has suggested a general physical mechanism of cellulose synthesis. The physical mechanism is that a certain number of chain initiators, or primers, are produced by each bacterium which then add on monomer units to form cellulose. Models for the synthesis, within the proposed physical mechanism, are described and examined in the light of DP measurements made on cellulose grown for different times. The model in which the average growing time of the chains is less than 40 min. is accepted; models invlving nonterminated chains and chains terminated at cell division are rejected. The DP measurements were made by a viscometric technique which permitted the use of never‐dried cellulose samples. Dried samples and their nitrates were found to be insoluble in their usual solvents. The viscosity average DP of the cellulose was found to be 3500; the mean average generation time of A. acetigenum was found to be 270 min.
The swelling of cellulose acetate networks obtained by crosslinking in solution
Authors: Rijke A. M. , Prins W.
Published: April 2003

In order to study the applicability of existing network theories for rubberlike polymers to crosslinked celluloseacetate networks, a series of gels was prepared by crosslinking cellulose acetate in dioxane solution with increasing amounts of oxalyl chloride. The swelling of these gels in dioxane, tetrahydrofuran, methyl acetate, and ethyl acetate as well as in cellulose acetate solutions of these solvents was determined by measuring their buoyancy in the swelling agent and in mercury on a slightly modified analytical balance. The solvent activity outside the gel in the case of the cellulose acetate solutions was determined osmometrically. An estimate of the extent of crosslinking was obtained by determinations of the oxalic acid content of the gels. On the basis of these experiments, it is found that Hermans' rather than Flory's theoretical expression for the conformational free energy, stored in the swollen network, is applicable. In the literature most experiments have been restricted to networks obtained by crosslinking in the dry state, and subsequently highly swollen. Under these conditions swelling experiments do not allow a discrimination between the two theories. The description of the swelling of crosslinked polymer networks requires at least three parameters, viz., (1) the molecular weight of the polymer chain between crosslinks Mp; (2) the solvent‐polymer interaction parameter x; and (3) the reference degree of swelling q0, in which state the polymer chains have their unrestrained mean square end‐to‐end distance (〈r20〉). The reference degree of swelling q0 varies with the swelling agent and the extent of crosslinking. From data of q0 as a function of (〈r20〉), which occurs at χ = 1/2, can be estimated. For the quantity (〈r20〉/Mp)1/2 the value 870 × 10−11 is found, which is well in line with values obtained for cellulose tributyrate and caprylate from viscosity data. Another estimate of the flexibility of the cellulose acetate chain yields a statistical chain element of about 10 monomer units. The general equilibrium swelling patterns of polymer networks in terms of the three parameters Mp, χ, and q0 are discussed and compared with the observed behavior of the cellulose acetate gels.
Chemical properties of bipolar electrolyte‐exchange resins
Authors: Mikes J. A. , Kovacs L. I.
Published: April 2003

Bipolar electrolyte exchangers were synthesized by introducing both acidic and basic ion exchange groups into the same skeleton of a styrene–divinylbenzene copolymer. The uptake of certain ions on resins of this kind differs from that achieved on monofunctional ion‐exchange resins of the same composition. Ferric ions, etc., are bound over the nominal capacity of the resins. A variation of the ratio of acidic to basic groups in the resin causes variation of the equilibrium data in certain ionic mixtures.
Orientation in nylon spherulites: A study by X‐ray diffraction
Authors: Mann J. , Roldan‐Gonzalez L.
Published: April 2003

A microbeam x‐ray diffraction method has been used to study orientation in spherulites grown from the melt of nylon 66 and in one case of nylon 610. It is concluded that in positively birefringent spherulites the crystallographic a axis is parallel to the spherulite radius. The zigzag extinction pattern shown by such spherulites in a polarizing microscope can be understood in terms of this orientation. The results on negatively birefringent spherulites are not in agreement with earlier results of Keller and it is suggested that further work on such spherulites is desirable. Evidence is cited which shows that zero birefringent spherulites have random orientation. The spheruloids or spheruloidal aggregates which grow at the same time as negatively birefringent spherulites are found to have well defined optical properties when grown in thin films and confused optical properties when grown in thick film. This difference is reflected in differences in the x‐ray diagrams. In thin films a unique orientation exists in which a direction close to the crystallographic b axis lies parallel to the radius while the (002) plane lies near the surface of the film. This orientation provides an explanation of the observed optical properties. In thick film the (002) plane again tends to lie near the surface of the film, but orientation relative to the radius varies from place to place, thus causing confused optical properties.
Molecular orbital calculation of monomer reactivity ratios
Authors: Levinson G. S.
Published: April 2003

The simple molecular orbital method is employed to calculate transition‐state conjugation energies which correlate well with observed monomer reactivity ratios. An examination of the model discloses the reasons it is possible to neglect both electronic repulsion and the fact that transition‐state separations are not the same for all monomerradical pairs. The parameters, Q and e, of the Alfrey‐Price treatment are compared to quantities calculated by the molecular orbital method.
Microscope investigations of extension and fracture in crystalline polymers
Authors: Yu Yung‐Fang , Ullman Robert
Published: April 2003

Thin films of polyethylene, polyhexamethyleneadipamide, polypropylene, and polyoxymethylene have been examined under the microscope during the application of a tensile stress. The response to stress in each case varies with the thermal history of the sample, and indeed this variation correlates closely with the size and type of spherulites formed during sample preparation. The particular behavior of each polymer has been described. In general, it is found that extension of the polymer under stress is usually possible if the spherulites are sufficiently small. In these four cases, long annealing brings about spherulitic growth and a brittle structure which fractures without extension when tension is applied.
Morphology of polypropylene spherulites
Authors: Inoue Masakazu
Published: April 2003

Dendritic spherulites of polypropylene were investigated in detail with the optical microscope. Dendrites grow and form twisted spherulites, and the twisting direction is clockwise toward the growing fronts. Dendrites could imbibe small spherulites on their tips, which seem to be elemental units of dendrites, and there are many knots on each branch of dendrites. In crystallization on a free surface, the supercooled polymer molecules involved in crystallization migrate to the growing fronts, and the resultant spherulites have oval structure. The thickness of the oval is larger than that of the parent film. The radial growth rates of dendrite are discussed.
Effects of impurities on the control of anionic batch polymerizations
Authors: Wenger Franz
Published: April 2003

The homogeneity of the molecular weight distribution of polymeric material is, in general, described fairly adequately by the homogeneity ratio ¯xw/¯xn. In recent literature on anionic polymerizations, the ¯xw/¯xn ratio implicitly has been used also for the evaluation of the polymerization control attainable in these processes with regard to the reproducibility and predictability of molecular weights. For polymerizations in which the monomer is added gradually, this procedure is sufficiently indicative, but leads to wrong conclusions in the case of batch polymerizations. For the evaluation of the latter processes, in addition to the ¯xw/¯xn ratio, the predictability ratio ¯x i.e., the quotient of the number‐average degree of polymerization calculated for an impurity level α to the one predicted in the absence of impurities (α = 0), or a related quantity, has to be known for both mono‐ and difunctional initiator. As a result of this investigation, batch polymerization methods which have attracted considerable attention in the literature with respect to the monodispersity of the products attained are found to be unsatisfactory from the point of view of polymerization control.
Kinetics of precipitation polymerization of vinyl chloride
Authors: Mickley Harold S. , Michaels Alan S. , Moore Albert L.
Published: April 2003

The polymerization of vinyl chloride in solution in tetrahydrofuran, and in cyclohexane, with AIBN initiator, has been studied over the monomer concentration range 3–14 mole/1. at 40 and 50°C., via a dilatometric technique. In tetrahydrofuran (a relatively good solvent for the polymer), polymerization rate is second order in monomer, and 0.7 order in initiator; DP is very low (∼100) at monomer concentrations below 10 mole/1. and relatively insensitive to monomer or initiator concentration. Below 10 mole/1. the reaction is either homogeneous, or the polymer separates as a solvated gel without evidence of autoacceleration. Above 10 mole/1., however, the polymer separates as a granular solid, autoacceleration is observed, and DP increases several fold. In cyclohexane (a poor solvent), polymer precipitates from the outset of the reaction, and autoacceleration is observed at all monomer concentrations. Polymerization rate is first order in monomer, half order in initiator, first order in polymer at low polymer concentration, and two‐thirds order in polymer at high polymer concentrations. DP is high, and essentially linear in monomer concentration. Results in tetrahydrofuran are interpreted as indicating that the solvent functions as a retarder, forming (by transfer from monomer) relatively unreactive radicals. In cyclohexane (as in bulk monomer), normal homogeneous kinetics govern the reaction in solution, but precipitated polymer particles function as secondary loci for propagation. A simplified moving‐boundary treatment of diffusion of radical activity into and out of a thin surface layer of a growing polymer particles satisfactorily accounts for the observed rate dependency on polymer concentration. Kinetic differences between the precipitation polymerization of vinyl chloride and acrylonitrile are believed attributable to the extremely high frequency of radical transfer to monomer in the former system.
Differential thermal analysis of fluoroelastomer systems
Authors: Paciorek K. L. , Lajiness W. G. , Lenk C. T.
Published: April 2003

Differential thermal analysis curves of diamine‐, peroxide‐, and magnesium oxidetreated vinylidene fluoride‐perfluoropropene copolymer show that crosslinking processes take place at ca. 140–200°C. A good state of cure is attained with amines (biscinnamylidene hexamethylenediamine) and benzoyl peroxide, although probably by different processes; magnesium oxide is much less effective. The vulcanized materials are less thermally stable than the untreated fluoroelastomer, as indicated by the lowered onset of decomposition. The effect is more significant in the amine‐cured materials; it can be deducted that amines, besides crosslinking the polymer, also modify it substantially, most likely by the formation of unsaturated centers.
Free‐radical copolymerization of α‐olefins with ethylene
Authors: Boghetich Luigi , Mortimer George A. , Daues Greg W.
Published: April 2003

Ethylene was polymerized at 15,000–25,000 psi at 130–220°C. with free‐radical initiators in the presence of 0–10% of C14‐labeled propylene, butene‐1, and octene‐1. Polymer composition was determined by scintillation counting. Molecular weight measurements and polymer unsaturation as detected by infrared analysis gave independent estimates of chain transfer. It was concluded that the major reaction of all α‐olefins is copolymerization: chain transfer is a minor reaction. For all α‐olefins, r1 (where ethylene is monomer 1) is 3.2–3.3 uncorrected, or 3.4–3.6 corrected for chain transfer.
Kinetics of anionic copolymerization. Determination of absolute rate constants
Authors: Smid J. , Szwarc M.
Published: April 2003

Lack of termination in the “Living” polymer systems enables one to determine directly the absolute rate constant of propagation and of copolymerization. Anionic polymerizations in tetrahydrofuran are usually very fast, and a flow technique was developed to determine the rate of these reactions. The method is described and its use illustrated by studies on the following systems: styrene–p‐methylstyrene, styrene–p‐methoxystyrene, and styrene‐2‐vinylpyridine. The results indicate that the polarity of the reacting monomer is the dominant factor in determining the value of the copolymerization rate constant as long as the polarities of the monomers involved are similar. However, the results obtained on the system styrene–2‐vinylpyridine clearly demonstrate that the terminal carbanion plays a major role when the polarities of the two monomers are very different. The technique can also be used to study the effect of the penultimate unit of a chain on the rate constant of propagation or copolymerization. Moreover, the chain length of the “living” polymer can be caried and its effect of the rate constant determined.
Transition metal catalysts. IX. Random ethylene‐propylene copolymers with a low pressure polymerization catalyst
Authors: Phillips G. W. , Carrick W. L.
Published: April 2003

Ethylene–propylene copolymers were prepared at atmospheric pressure with the VCl4–(C6H5)4Sn–AlBr3, hydrocarbon‐soluble, polymerization catalyst. A controlled rate of initiation and thus a constant comonomer composition were obtained by the introduction of a constant amount of oxygen into the monomer stream. Four copolymers, containing 2.6, 3.8, 10, and 27 mole‐% propylene, were found to have uniform comonomer compositions when fractionated by successive extraction with boiling solvents, in contrast to copolymers prepared with other reported Zieglertype catalysts. An elution fractionation of the 10 mole‐% propylene copolymer was conducted with cellosolve‐xylene mixtures above the copolymer melting point. The molecular weight distribution was shown to approximate the “most probable” distribution. This is in agreement with a previously proposed polymerization mechanism. The propylene contents of each of the fractions from the 10% copolymer were within ±1% propylene of the value of the whole copolymer. This narrow composition distribution is in accord with the statistical distribution predicated theoretically for random copolymers and is in accord with the previous finding that r1r2 ≅ 1. These data suggest that Ziegler‐type catalysts containing a single active species are amendable to the same statistical and kinetic treatment that has been used for the classic polymerization catalysts.1

Phillips, G. W., and W. L. Carrick, J. Am. Chem. Soc., 84, 920 (1962).
Differential thermal analysis of high polymers. V. Ethylene copolymers
Authors: Ke Bacon
Published: April 2003

Melting and crystalline properties of methyl‐and ethyl‐branched polymethylenes—models for ethylene‐propylene and ethylene–α‐butene copolymers—containing up to 20 branches per 1000 carbon atoms have been investigated by differential thermal analysis (DTA). The melting‐point depression is practically linear with branch concentration. However, ethyl groups are more effective than methyl groups. Cooling at different rates during annealing produces a wider melting‐point spread in copolymers containing more branches. Again, copolymers containing ethyl groups are affected more than those having an equal number of methyl groups. Copolymer crystallinity estimated by DTA also decreases linearly with the number of branches; ethyl groups disrupt crystallinity more markedly than methyl groups do. The effect of colling rates on crystallinity increases with branch concentration. Melting and crystalline behavior of two commercial ethylene copolymers agree with patterns derived from the models. The thermogram of a crystalline ethylene‐propylene block copolymer consists of two separate melting peaks corresponding to crystalline regions formed by ethylene and propylene sequences. Total crystallinity of this copolymer was estimated and used in calculating the copolymer composition. Restrictions for crystallization in the block copolymer are apparent from the thermogram.
An expression for orientation in cellulose fibers
Authors: Gupta V. D.
Published: April 2003

Hermans' orientation factor can be evaluated only when the diatropic and paratropic interferences arise from planes which form an orthogonal set. This is only approximately satisfied in case of both cellulose I and cellulose II. In the present communication an exact expression has been derived which can be evaluated from x‐ray measurements, angle between face normals of paratropic interferences, and the optical constants.
The contribution of internal energy to the elastic force of natural rubber
Authors: Roe R.‐J. , Krigbaum W. R.
Published: April 2003

Data are reported for the temperature coefficient of the retractive force for a natural rubber sample which had been crosslinked by irradiation. These measurements differ from those previously reported in allowing a longer interval for the attainment of equilibrium, in covering a wider range of elongations, and in a somewhat greater precision of the tension measurement. The Mooney equation constants for the tension at 45°C. are 2C1 = 2.617 kg./cm.2 and 2C2 = 0.876 kg./cm.2. The latter, although smaller than the values reported by other workers for similar samples, is far from vanishing. A comparison is given of (∂f/∂T)V,L as evaluated from the measured (∂f/∂T)V,L according to various proposals. Approximately 20% of the total force arises from the internal energy contribution, fe, when the relative elongation, α, is near unity. The fe/f ratios calculated from our measurements stand in good agreement with those obtained from Ciferri's data, despite the fact that the latter correspond to a much larger C2 value. Furthermore, both sets of data indicate that fe/f decreases with increasing α. The entropy component of the force, when fitted to the Mooney equation, yields C1s ≅ C1 but C2s < C2. This suggests that the C1 term is primarily due to entropy effects, whereas the internal energy makes a larger contribution to C2. The nonvanishing C2 and the variation of the fe/f ratio with α, represent deviations from the gaussian model treatment of Flory, Hoeve, and Ciferri. Criferri and Flory have expressed the opinion that finite C2 values arise solely from the failure to attain mechanical equilibrium. However, the cubic lattice model treatment of Krigbaum and Kaneko indicated that although the two discrepancies cited above may be accentuated by nonequilibrium effects, they can only be expected to vanish under equilibrium conditions in the limit of infinite chain length between crosslinks.
Solution‐grown polyethylene dendrites
Authors: Wunderlich Bernhard , Sullivan Peter
Published: April 2003

Polyethylene has been crystallized from toluene solution under varying conditions of quenching. The concentration, temperature gradient, pressure, and viscosity has been varied. Depending upon the conditions, different dendrites were found. The dendrites were named in accordance with their appearance: epitaxial dendrites, rightangle dendrites, six‐ended dendrites, and hedgehog dendrites. The resulting structures were analyzed with an interference microscope and with a polarizing microscope. On flattening dendrites on the microscope slide, regular structures with a weak birefringence of 0.0026 and an average refractive index of 1.527 ± 0.009 were found. The dendrites have a bundlelike appearance in three dimensions with a strong birefringence (∼0.07). Correlation to single crystal growth from solution and spherulitic growth from the melt has been attempted.
Reactions of carboxylated butadiene–styrene rubbers and their mixtures with ε‐caprolactam induced by γ‐radiation
Authors: Mladenov I. , Tutorskiǐ I. A. , Dogadkin B. A.
Published: April 2003

Carboxylated butadiene–styrene rubber containing various amounts of styrene and methacrylic acid were exposed to 0.1–50 Mr doses of γ‐radiation from a Co60 source. This irradiation resulted in a decrease in the carboxyl group content, particularly at low doses. The radiochemical yield of crosslinked polymers at low doses is a linear function of the carboxyl group content of the initial polymer. The number of crosslinks formed by the carboxyl groups at doses up to 20 Mr calculated from the maximum swelling data was found to agree satisfactorily with the number of crosslinks as calculated from the carboxyl group consumption. Irradiation of the carboxylated rubber in mixtures with ε‐caprolactam gives rise to addition of the latter to the rubber with formation of insoluble compounds. The amount of caprolactam combining with the rubber increases linearly with an increase in ε‐caprolactam content of the original mixtures in the range of 5–50%. There is also an increase in the degree of crosslinking. An increase in the bound ε‐caprolactam content leads to an increase in the tensile strength of the polymer.
Polymerization of methyl methacrylate by triethylboron–oxygen mixtures
Authors: Welch F. J.
Published: April 2003

The effect of oxygen on the rate of polymerization of methyl methacrylate catalyzed by triethylboron has been investigated at temperatures in the range 0–52°C. In the absence of oxygen polymerization does not occur, but formation of polymer begins immediately on admission of oxygen. Polymerization is characterized by a decrease in rate with increasing conversion which is most pronounced when the concentrations of oxygen and triethylboron are greatly different. The initial rate of polymerization is proportional to the square root of the oxygen concentration and inversely proportional to the degree of polymerization of poly(methyl methacrylate) formed, confirming the radical nature of the polymerization. The apparent activation energy for the polymerization was unusually low, only 4 kcal./mole. A mechanism in which initiating radicals are produced by a sequence of reactions involving autoxidation of the boron alkyl to peroxide followed by induced decomposition of the peroxide by excess boron alkyl is suggested.
γ‐initiated crosslinking of unsaturated polyesters
Authors: Burlant W. , Hinsch J.
Published: April 2003

Unsaturated polyesters containing 1.5, 3.2, and 4.8 double bonds per molecule (derived from maleic anhydride, phthalic anhydride, and propylene glycol) were crosslinked by γ‐rays from Co60. From sol fraction data and from measurements of the molecular weight between crosslinks of the corresponding gel, it is concluded that for polymers containing more than about 4 double bonds per molecule, γ‐initiated bond formation is in accord with the reported chain reaction scheme for such systems. At lower degrees of unsaturation, a significant fraction of the initially available unsaturated sites has been consumed at the gel point so that subsequent radiation (and radical formation), which effects chain growth at the expense of intramolecular crosslinking, appears to be in part, a random process. It is suggested that radiation‐induced changes in unsaturated polyesters are best described in terms of the simultaneously occurring chain growth and intramolecular crosslink formation.
Crystallization kinetics of poly‐3,3‐bis(chloromethyl) oxacyclobutane
Authors: Inoue Masakazu
Published: April 2003

The crystallization kinetics of poly‐3,3‐bis(chloromethyl) oxacyclobutane has been investigated by the method of dilatometry, and at the same time the growth rate of spherulites was measured under the polarizing microscopy. Isothermal crystallizations of this polymer were carried out at constant crystallization temperature over the range of 150–160°C., and the rate constants were calculated by the Avrami equation. Crystallization proceeds through a mechanism of homogeneous nucleation and fibril growth. The growth rates of spherulites were measured at various constant crystallization temperatures of 75–140°C. Under a polarizing microscopy, the spherulites formed are seen to be of two morphological types; one is four‐cornered and another is petal‐shaped.
Preparation of regularly alternating polyesteramides
Authors: Williams J. L. R. , Laakso T. M. , Contois L. E.
Published: April 2003

Regularly alternating polyesteramides with glycol components ranging from C2 to C14 and interamide linkages ranging from 2 to 6 have been prepared by high‐temperature polycondensation of performed bisesteramides with sodium hydrogen tetrabutyltitanate as catalyst.
Magnetic anisotropy effects in broadline NMR spectra of polytetrafluoroethylene
Authors: Wilson Charles W.
Published: April 2003

The effects of molecular magnetic anisotropy upon the broadline NMR spectrum of a bulk polymer have been recognized and measured for the first time. The F19 NMR absorption spectra in polytetrafluoroethylen (PTFE) show a line‐shape asymmetry over a broad range of temperatures which can be explained by the magnetic anisotropy of C‐F bonds. Nuclear magnetic resonance studies of PTFE samples whose crystalline regions are aligned by cold drawing have made possible an estimate of the anisotropy of C‐F bonds in this material: Δσ, the magnetic anisotropy of the screening constant, is found to be 171 ± 15 ppm; the screening of each F19 nucleus is paramagnetic, being maximum when the direction of its C‐F bond is perpendicular to the large static magnetic field and minimum (probably zero) when parallel. Static magnetic susceptibility measurements of PTFE show the predicted diamagnetism, and only a small (<5%) static magnetic anisotropy of the molecular crystals is found.
Infrared studies of popcorn polymerization. I. Oxidation of butadiene popcorn polymer
Authors: Miller Glenn H. , Larson Virginia R. , Pritchard Glyn O.
Published: April 2003

An infrared analysis of butadiene popcorn polymer showed the structure to be highly unsaturated with all of the groupings around the double bonds in the trans‐position. The oxidation of the polymer produces aldehydes and ketones, but due to the nature of the infrared‐pelleting technique which had to be used, it was not possible to resolve the broad spectral peaks for the positive identification of other structures. There was no apparent loss of unsaturation during the oxidation process. The loss in popcorn polymer growth activity shown when it is reseeded above fresh butadiene monomer is attributed to the loss of the hydrogen atoms that could participate in a transfer reaction. The latter is undoubtedly responsible for much of the rapid growth phenomena exhibited by this type of polymer.
Viscoelastic properties of amorphous selenium
Authors: Eisenberg A. , Tobolsky A. V.
Published: April 2003

Viscoelastic properties of amorphous selenium were studied by stress relaxation, creep, and a new technique described in this paper. A master curve was obtained as well as maximum relaxation times at several temperatures. The glass transition temperature was obtained from volume‐temperature relations. A technique is described for the study of hard viscoelastic materials.
Stereospecific polymerization of acetaldehyde. Part I
Authors: Ishida Shin‐Ichi
Published: April 2003

Stereospecific polymerization of acetaldehyde by triethylaluminum was studied. It was found that some catalyst was made at room temperature or at a low temperature and that the effective catalyst of the polymerization was the reaction product of organometallic compound and water contained in aldehyde. When addition is made at room temperature, Polymerization proceeds more rapidly than when at low temperature. and there is a miximal conversion at a certain concentration of catalyst. Because the maximal catalytic activity occurred at a molar ratio of H2O/ALEt3 of about 0.5, the effective catalyst is considered to be tetraethyl dialumoxane not but triethylaluminum itself. It is considered that the dialumoxane produced the stereogularity in the present case. Crystalline polyacetaldhyde was formed even in a homogeneous solution. The polarity of solvent did not completely destroy the stereospecificity but reduced the yield of polymer in spite of the ionic nature of the polymerization. Clear relationships were obtained between the dipole moment, or the logarithm of dielectric constant of the solvent used, and the conversion. It was found that there is a critical temperature near −40°C., above which polymer could not be obtained, and that as the temperature was lowered below −40°C. the rate of reaction was increased, showing negative temperature coefficient. The critical temperature −40°C., may be regarded as a ceiling temperature for the polymerization of acetaldehyde.
Polymerization of 2,4,6‐triallyloxypyrimidine
Authors: Clampitt Bert H. , Mueller Arthur P.
Published: April 2003

The preparation of trallyloxypyrimidine is described, together with the polymerization characteristics of this compound under differential thermal analysis conditions. The DTA curves show a doublet first exotherm near 100°C, and a singlet exotherm at 225°C. Combining the heat values obtained from the DTA curves with infrared spectral data indicates that the complex first exotherm represents a total polymerization of two allyl groups, while the second exotherm involves rearrangment to the barbiturate structure. The fact that the last allyl group does not polymerize during the second exotherm is due to the presence of a hydroxyl group in the rearranged structure. The results are compared to a previous study of the reaction mechanism of triallyl cyanurate polymerization.
The polymerization reaction in liquid sulfur dioxide. Part VIII. The effect of aromatic compounds on the cationic polymerization of styrene in liquid sulfur dioxide
Authors: Tokura Niichiro , Matsuda Minoru , Watanabe Yasuaki
Published: April 2003

The cationic polymerization of styrene in liquid sulfur dioxide was conducted at −10°C. in the presence of hydrocarbons such as benzene, toluene, p‐xylene, p‐cymene anisole, cyclohexane, and chlorobenzene diluted with carbon tetrachloride and with boron trifluoride etherate as catalyst. When aromatic hydrocarbons were added to the polymerizing system in liquid sulfur dioxide, both overall rate and degree of polymerization decreased with increasing of hydrocarbon concentration. On the other hand, the rate and degree of polymerization increased as the concentrations cyclohexane or chlorobenzene added increased. When anisole was used, polymerization was completely inhibited. The order of solvent participation n on the polymerization in liquid sulfur dioxide was obtained. The magnitude and the sign of n is discussed and explained by interaction of the added solvent with the active carbonium ion of the growing chain and with liquid sulfur dioxide.
Trifluoronitrosomethane/tetrafluoroethylene copolymer: Degradation by heat and by radiation
Authors: Shultz A. R. , Knoll N. , Morneau G. A.
Published: April 2003

Thermal degradation of trifluoronitrosomethane/tetrafluoroethylene copolymer yields COF2 and CF3NCF2 as gaseous decomposition products. The copolymer weight loss appears first order in copolymer. The activation energy is 58 kcal./mole, and the first‐order rate constant is approximately k1 (min.−1) = 3.1 ′ 1021 exp {‐29,047/T} determined in the 250–265°C. range. A rather large weight fraction of low molecular weight species exists in some nonfractionated copolymer samples leading to rapid initial weight losses upon heating. Thermogravimetric and differential thermal analyses were used to observe a thermal runaway decomposition at temperatures above 270°C. Gamma radiations from spent atomic fuel elements produce random scissions in the copolymer chains followed by COF2 and CF3NCF2 evolution. At 23°C. the total energy absorption per primary chain scission is Ed = 44 e.v./scission. For each chain scission an average of approximately 5.3CF2N(CF3)OCF2 units decompose to COF2 and CF3NCF2. In systems containing these product gases at appreciable pressure an adduct, (CF3)2NCOF, is produced. Ultraviolet light of 2537 A. wavelength photolyzes the copolymer producing random chain scissions and the gases COF2 and CF3NCF2. The quantum yield for primary random chain scission at 23°C. is ϕd = 0.91 × 10−3 scissions/absorbed photon; the equivalent total energy absorption per event is Ed = 5400 e.v./scission. An average of approximately 3.6 CF2N(CF3)OCF2 units decompose to COF2 and CF3NCF2 for each chain scission.