bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract3,9‐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

AbstractDie 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

AbstractDie 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

Abstractα‐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

AbstractA 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

AbstractWe 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

AbstractMeasurement 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

AbstractIn 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

AbstractBipolar 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

AbstractA 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

AbstractThe 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

AbstractThin 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

AbstractDendritic 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

AbstractThe 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

AbstractThe 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

AbstractDifferential 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

AbstractEthylene 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

AbstractLack 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

AbstractEthylene–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.1Phillips, G. W., and W. L. Carrick, J. Am. Chem. Soc., 84, 920 (1962).