bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology and growth of extended chain crystals of polyethylene
Authors: Wunderlich Bernhard , Mielillo Louis 
Published: April 2003

AbstractThe morphology and growth of extended chain crystals of polyethylene is discussed on the basis of optical and electron microscopy. The spherulitic habit is shown to be caused by nucleation of new lamellae on the (001) surface of lamellae, branching of lamellae on their growth face, and thickening of lamellae. Spherulite centers have been identified down to the primary lamella. Analysis of intersections of lamellae during crystallization allowed the identification of intermediate stages of crystal growth. Fracture surfaces parallel to the growth face and the (001) face are discussed. “Ripple decoration” by surface recrystallization is developed as a tool for fracture surface study. Kink bands are described as growth defects. Bending of lamellae is shown to go by slip parallel to the polymer chains. Ripple and drawn out fiber annealing is analyzed. All observations on extended chain crystals are used to propose a mechanism of extended chain crystal growth of polyethylene under elevated pressur.
Statistical thermodynamics of polymer crystallization
Authors: Peterson J. M. , Lindenmyer P. H. 
Published: April 2003

AbstractA model has been assumed in which 1. chain folding if it occurs at all, is regular, 2. chain ends do not enter the crystal, and 3. no fractionation takes place except the rejection of all molecules from the crystal whose lengths are shorter than the crystal thickness. According to this model it is shown that the entropy contribution of the non‐crystalline sections of a partially crystallized chain is roughly constant per molecule and is inconsequential relative to the free energy of crystallization. By assuming a molecular weight distribution function and using polyethylene as an example, the free energy vs. crystal thickness shows a minimum. The crystal thickness predicted by this minimum is in reasonable agreement with observations and the predicted temperature and molecular weight variations are qualitatively in agreement with experiment.
Reversible long period variations with temperature in single crystals of branch‐containing polyethylenes
Authors: Dawkins J. V. , Holdsworth P. J. , Keller A. 
Published: April 2003

AbstractThe variation with temperature of the small‐angle X‐ray diffraction patterns from annealed single crystal mats of linear polyethylene and a number of branched polyethylenes has been examined. On cycling the temperature between room temperature and the annealing temperature the intensities of the small‐angle reflections of all the samples were observed to change reversibly. However, in the case of the branched polyethylene mats, these changes were accompanied by significant reversible changes in the X‐ray long periods. These reversible long period changes were attributed to reversible changes in the thickness of the lamellar crystals of which the mats were composed. Possible explanations for this behaviour, and its significance to existing ideas of polymer crystallization, are briefly discussed.
Etude par diffusion de la lumière des hétérogéneités rencontrées dans les solutions de polyoxyéthylène
Authors: Strazielle Par Claude 
Published: April 2003

AbstractNous avons étudié par diffusion de la lumière un certain nombre d'échantillons de polyoxyéthylène de masses moléculaires comprises entre 10.000 et 350.000.Suivant les conditions expérimentales adoptées, les intensités diffusées peuvent ětre perturbées par des hétérogénéités.Nous avons mis en évidence la formation de cristaux lorsque les solutions sout filtrées sur des filtres fins à 25°C, ils sont peu résistants et disparaissent à 40°C.Pour les échantillons de masses moléculaires élevées, les solutions contiennent une partie hétérogène qui résiste à des températures supérieures à la températur de fusion du Polymère, mais les agrégats sont éliminés par filtration.Nous avons enfin étudié la diffusion due à la partie hétérogène afin d'obtenir certaians renseignements comme le pourcentage et les dimensions des agrégats ou des cristaux en solution.
Aqueous polymerization of acrylamide initiated by permanganate/oxalic acid redox system
Authors: Misra G. S. , Shukla J. S. , Narain Harish 
Published: April 2003

AbstractThe polymerization of acrylamide initiated by permanganate/oxalic acid redox pair has been studied in aqueous media at 35 ± 0.2°C in nitrogen atmosphere.The rate of polymerization is independent of activator (oxalic acid) concentration (0.75·10−3 to 7.5·10−3 mole/l.) except at very high (above 7.5·10−3 mole/l.) or very low (below 0.75·10−3 mole/l.) concentrations of the activator. The rate varies linearly at low monomer concentration. The catalyst exponent decreases from nearly unity to 0.65 with the increase in the concentration of catalyst (KMnO4) probably due to participation of primary radicals in the termination of the growing chain.The initial rate increases with increase in the polymerization temperature. The overall energy of activation has been found to be 11.97 Kcal/mole within the temperature range 25‐50°C.Organic solvents (water miscible only) and salts (KCI, Na2SO4) depress the initial rate but small amounts of manganous salts (MnSO4) can increase the initial rate to a considerable extent. High concentration of salts (Na2SO4, KCl, and MnSO4) causes termination of the growing chain. A complexing agent, NaF, decreases the initial rate but the limiting conversion is increased.Introduction of new catalyst at intermediate stages of polymerization increases both the rate and the limiting conversion.
Kinetics of the formation of cellulose xanthate in homogeneous medium
Authors: Andersson Lennart , Samuelson Olof , Törnell Bertil 
Published: April 2003

AbstractThe total rate of xanthation of low molecular weight cellulose in a homogeneous medium was studied spectrophotometrically using a stopped flow technique. By combining these results with determinations of the number of primary and secondary xanthate groups, the individual rate constants for the formation of these groups were calculated.The results show that the xanthate formation is a second order reaction determined by the concentrations of carbon disulfide and alcoholate.
Vinylpolymerisation. 216. Mitt. polmerisation von methylencycloalkanen
Authors: Takemoto Von Kiichi , Izubayashi Masuji , Imoto Minoru 
Published: April 2003

AbstractDie Polymerisation sowie due Copolymerisation von Methylencyclobutan, ‐cyclopentan und ‐cyclohexan wurden untev verschiedenen Bedingungen untersucht. Es ergab sich, daß Methylencycloalkane nicht homopolymerisieren, aber radikalisch mit einigen Vinylmonomeren ziemlich leicht copolymerisiert werden können. Die Aktivierungsenergien sowieentropien bei der Copymermerisation von Methylencycloalkanen wurden ermittelt.
Studies on new chemical resistant polyesters based on bisphenol‐a derivatives
Authors: Gupta S. K. , Sharma Y. N. , Thampy R. T. 
Published: April 2003

AbstractBisphenol‐A (I), 2.2‐di(4‐hydroxy‐3.5‐dibromophenyl)‐propane(IA) and 2.2‐di(4‐hydroxy‐3.5‐dichlorophenyl)‐propane(IB) were condensed with methyl chloroacetate to give isopropylidene bis(p‐phenyleneoxy)‐di‐methyl acetate (II) and its bromo‐ (IIA) and chloro‐ (IIB) derivatives, respectively. Based on compounds II, IIA, and IIB, three new polyesters were synthesised. These polyesters were evaluated for hydrolytic stability, heat distortion point, vicat needle point, flame resistance, and thermogravimetric analysis. They have vicat needle points comparable with hexachloro‐endo‐methylene tetrahydrophthalic acid (HET) based polyester. Resins based on IIA and IIB have 20 times better hydrolytic stability than HET isophthalate resin. Thermogravimetric analysis showed that resin based on compound II has highest 50% decomposition temperature out of these polyester resins.
Synthese und halbleitereigenschaften einiger komplexe und der aus ihnen hergestellten polymeren. Teil 2. Polymere mit phthalocyaninartiger und triazinartiger stuktur
Authors: Manecke Von Georg , Wöhrle Dieter 
Published: April 2003

AbstractPolymere mit phthalocyaninrtiger Struktur ergaben sich durch Reaktion von einigen schwefelhaltigen Komplexen, die vier Nitrilgruppen enthalten, mit Kupferacetylacetonat bei höherer Temperature. Die Leitfähigkeiten der Polymeren liegen zwischem 6,3·10−3 und 2,1·10−10 Ohm−1cm−1. Die Aktivierungsenergie zeigt Werte mit einer unteren Grenze von 0,04 eV. Durch Erhitzen einiger Tetracyanverbindungen in Chinolin wurden Polymere mit triazinartiger Struktur erhalten, die Leitfähigkeiten bis zu 3,9·10−2 Ohm−1cm−1 aufweisen.
Unterschiedlicher verlauf der phosphorolytischen amylosesynthese mit maltotriose und höheren maltodextrinen als starter
Authors: Pfannemüller Von B. , Burchard W. 
Published: April 2003

AbstractDas unterschiedliche Starterverhalten von Maltotriose einerseits und Maltotetraose und Maltohexaose andererseits bei der Synthese von Amylosen durch Kartoffelphosphorylase wird untersucht. Die Synthese verläuft in jedem Fall nach einem Mehrkettenmechanismus. Mit Maltotetraose und Maltohexaose als Starter werden Amylosen mit einer POISSON‐Verteilung synthetisiert. Die mit Maltotriose als Starter synthetisierten Amylosen setzen sich degegen aus einem einheitlichen, hochmolekularen Anteil und einem uneinheitlichen, niedermolekularen Anteil zusammen. Es wird gezeigt, daß die Unterschiede in der Molekulargewichtsverteilung darauf beruhen, daß bei Synthesen mit Maltotriose für die Startreaktion eine 400 mal kleinere Geschwindigkeit gefunden wird als für die Wachstumsreaktion, während bei Synthesen mit Maltotetraose und Maltohexaose Start‐ und Wachstumsreaktion gleiche Geschwindigkeit besitzen.
Penultimate unit effect in the copolymerization of alkyl methacrylates and styrene
Authors: Chaudhuri Ajit Kumar , Palit Santi R. 
Published: April 2003

AbstractKinetics of bulk copolymerization of styrene and alkyl methacrylates, namely, ethyl, isobutyl and n‐nonyl methacrylate have been investigated at 60°C, and the extent of diffusion‐controlled termination in these systems has also been checked. Rate‐composition curves reveal that addition of a small amount of styrene in pure alkyl methacrylates markedly reduces the rate of polymerization, the effect becoming more important as the chain length of the ester group is increased. With higher alkyl methacrylates, the position of the minima in the curves shifts towards a lower concentration of styrene in the feed. The applicability of ARLMAN'S theory on the variation of the Φ‐factor with monomer feed composition has been examined.
Studies on amylose and its derivatives. Part VII. Melting and glass transition temperatures of amylose esters
Authors: Cowie J. M. G. , Toporowski P. M. , Costaschuk F. 
Published: April 2003

AbstractVarious amylose esters ranging from the acetate to the caproate were prepared. Melting and glass transition temperatures were measured for each and it was observed that both Tm and Tg were depressed as the chain length of the substituted ester side chain was increased. By assuming this to be an internal plasticization process, estimates of Tm ≃ 800°K and Tg ≃ 590°K were obtained for the unsubstituted amylose molecule. An average value of (Tg/Tm) of 0.80 was calculated for these esters which would suggest that they are moderately rigid, unsymmetrical polymers.
Über wasserstofffbrücken in polyamiden
Authors: Bessler Von Eberhard , Bier Gerhard 
Published: April 2003

AbstractDie Temperaturabhängigkeit der IR‐Spektren verschiedener Polyamide im Gebiet der NH‐Valenzschwingen wurde im Temperaturbereich zwischen 25 und 250°C untersucht. In weitgehender übereinstimmung mit anderen Autoren wurde gefunden, daß bei teilkristallinen Polyamiden der relative Anteil der nicht über Wasserstoffbrücken gebundenen NH‐Gruppen unterhalb deren Schmelzpunkt unerheblich ist (unter 1%). In der Nähe des Schmelzpunktes nimmt der Anteil der freien Amidgruppen jedoch sprunghaft zu. Bei zwei amorphen Polyamiden aus Terephthalsäure und verzeigten Diaminen wurde bei Zimmertemperatur ein wesentlich höherer Anteil von freien NH‐Gruppen gefunden (mehrere Prozent) als bei den teilkristallinen aliphatischen Polyamiden. Bei den beiden amorphen Polyamiden ändert sich der relative Anteil freier NH‐Gruppen im untersuchten Temperaturbereich annähernd linear mit der Temperatur, wobei die Zunahme über der Glastemperatur stärker ist als unter der Glastemperatur. Bei höheren Temperaturen (gemessen 230°C) wird für alle untersuchten Polyamide ein Anteil freier NH‐Gruppen von 10–20% abgeschätzt.
Synthesis of mixed polysaccharides based on cellulose
Authors: Gal'braikh L. S. , Rogovin Z. A. , Belyakova M. K. , Polukhina S. I. 
Published: April 2003

AbstractThe alkaline saponification of cellulose tosylates containing the tosyloxy group at various carbon atoms of the basic unit has been studied. It has been found that this reaction leads to the formation of mixed polysaccharides containing 2.3‐ and 3.6‐anhydrorings. The monosaccharide composition of mixed polysaccharides which are anhy droderivatives of cellulose has been determined.The stereochemistry of the opening of α‐oxide rings in 2.3‐anhydroderivatives of cellulose has been considered. It is shown that the opening of 2.3‐anhydrorings by acidic and basic reagents takes place under predominant formation of basic units with altro‐configuration of the substituents on secondary carbon atoms.An investigation has been carried out with respect to the reaction of 2(3)‐O‐tosylcellulose with ammonia in methanol and DMF and with potassium acetate in phenol. It has been established that these reactions proceed through the intermediate stage of the formation of 2.3‐anhydrorings. The synthesis of mixed polysaccharides with glucose, 3‐aminoaltrose, and 2‐aminoglucose on the one hand and with altrose and glucose as basic units on the other hand is described.By the reaction of mesylcellulose with potassium acetate in phenol the synthesis of mixed polysaccharides with gluco‐ and mannopyranose units has been realized.
The influence of chain transfer agents on rate of polymerization in the heterogeneous and homogeneous polymerization of vinyl chloride
Authors: Breitenbach J. W. , Olaj O. F. , Reif H. , Schindler A. 
Published: April 2003

AbstractThe addition of small amounts of effective chain transfer agents such as carbon tetrabromide and dodecyl mercaptane to the azo‐iso‐butyronitrile‐initiated polymerization of vinyl chloride in 1.2‐dichloroethane leads to a marked increase in the rate of polymerization which, although lesser than in the heterogeneous bulk polymerization of vinyl chloride, amounts to approximately 20% in this completely homogeneous system. At higher transfer agent concentrations due to the slightly retarding action of the transfer agent a decrease in rate is to be observed so that maximum rates are obtained with 3ċ10−4 moles of transfer agent per mole of monomer. As in the heterogeneous bulk polymerization the increase of rate is explained by a transformation of the less active radicals formed by chain transfer to monomer into the more active radicals derived from the chain transfer agent, leading to an increase in kinetic chain length. The influence of the chain transfer agent on the heterogeneous and homogeneous polymerization of vinyl chloride is compared and a kinetic scheme, which is representative for both cases, is established and discussed in detail.
Radiation induced solid state polymerization of derivatives of methacrylic acid. VI. Polymerization of barium methacrylate dihydrate during irradiation
Authors: Bowden M. J. , O'Donnell J. H. , Sothman R. D. 
Published: April 2003

AbstractCrystalline barium methacrylate dihydrate polymerized during gamma irradiation at 15–35°C. Sigmoidal shaped conversion curves were obtained. The induction period decreased markedly with increase in temperature or dose rate. The polymerization rate(approximately constant from 25–75% conversion) increased with dose rate, corresponding to an exponent of about 0.5, but was almost independent of temperature. ESR spectra showed that the radical concentration increased linearly with time from the commencement of irradiation giving G(radicals) = 7.6 ± 0.5 at 25°C and the same value at 15°C. The radical concentration decreased during the polymerization period, but then increased again. The induction period was attributed to physical trapping of short‐chain propagating radicals.
Die radikalausbeute beim thermischen zerfall von azoisobuttersäuredinitril in gegenwart von sauerstoff und in methylmethacrylat als lösungsmittel
Authors: Vogt Von Walter , Dulog Lothar 
Published: April 2003

AbstractDie Radikalausbeute, gekennzeichnet durch den Radikalausbeutefaktor ε (efficiency), beim thermischen Zerfall von Azoisobuttersäuredinitril (AIBN) in sauerstoffhaltigen Lösungen wurde mit Hilfe zweier direkter chemisch‐analytischer Methoden bestimmt, die sich gegenseitig ergänzen. Die 1. Methode beruht auf der gaschromatographischen Bestimmung des durch Kombination der primären 2‐Cyanoisopropylradikale entstehenden Tetramethylbernsteinsäuredinitrils; sie liefert einen Wert für (1‐ε). Die 2. Methode beruht auf der jodometrischen Bestimmung von 2‐Cyanoisopropylhydroperoxid und p‐Benzochinon, die letztlich durch eine Abfangreaktion mit Hydrochinon aus den der primären Kombination entgangenen Radikalen entstehen; sie liefert direkt einen Wert für ε. Nach beiden Methoden wurde übereinstimmend bei dem System Methylmethacrylat/AIBN/O2/Hydrochinon und bei 90°C ein Wert von ε + 0,810 ± 0,005 erhalten. Zwischen 70 und 100°C steigt ε dabei linear von 0,785 ± 0,005 auf 0,833 ± 0,005. Für n‐Propylacetat und Toluol als Lösungsmittel wurde bei 90°C der gleiche ε‐Wert wie für das Methylmethacrylat gefunden, nämlich 0,813 ± 0,005 und 0,810 ± 0,005.
Kinetik der äthylenpolymerisation mit löslichen Ziegler‐Nnatta‐katalysatoren
Authors: Reichert Von K. H. , Schubert E. 
Published: April 2003

AbstractEs wird über die Kinetik der Polyreaktion von Äthylen und Äthylen‐d4 mit dem homogenen ZIEGLER‐NATTA‐Katalysator (C5H5)2TiCl2/Al(C2H5)2Cl und einigen seiner Homologen in Benzol als Lösungsmittel berichtet.Hiernach ist die Polyreaktion des Äthylens als Nebenreaktion der Reaktionsfolge des Katalysatorsystems anzusehen und setzt sich aus einer Start‐, Wachstums‐, Abbruch‐ und Übertragungsreaktion zusammen. Die Geschwindigkeitskonstanten der Teilreaktionen für den homogenen und heterogenen Polymerisationsbereich werden angegeben. Für die miximale Bruttopolymerisationsgeschwindigkeit im heterogenen Bereich wurde folgende Abhängigkeit ermittelt:

Als polymerisationsaktive Spezies wird ein Titan(IV)‐Aluminium‐Komplex mit brükkenständiger Äthylgruppe vorgeschlagen. Wachstum soll hierbei nach erfolgter Aktivierung des Monomeren durch Insertion zwischen die im Komplex exo‐ständige Titan‐Kohlenstoffbindung vorsichgehen.
The reaction of propane sultone with macromolecules. III. Poly(ethylene imine)
Authors: Natus Guy , Goethals Eric J. 
Published: April 2003

AbstractThe reaction of propane sultone with poly(ethylene imine) (PEI) has been studied in benzene and in methanol. The reaction products are polyampholytes insoluble in water or any other solvent, but soluble in strong alkali or in concentrated acids. Depending on the molar ratio PEI: propane sultone, products having a degree of substitution between 0.23 and 0.64 were obtained. After treatment with excess sodium hydroxide and removal of the excess by dialysis, a polymer containing both sodium sulfopropyl groups and sulfopropyl groups in form of inner ammonium salts was obtained.
Thermodynamics of polymerisation of heterocyclic compounds. Part. III. The heat capacity, entropy, enthalpy, and free energy of tetroxan
Authors: Clegg G. A. , Melia T. P. 
Published: April 2003

AbstractA precision, adiabatic vacuum calorimeter and a differential scanning calorimeter have been used to measure the heat capacity of tetroxan over the temperature range 80 to 420°K. An estimate has been made of heat capacity values below 80°K. Values of the heat capacity, entropy, enthalpy, and free energy are listed at 10° intervals. Values of 22.6 ± 0.4 kJ · mole−1 and 385 ± 1°K are obtained for the heat of fusion and melting temperature, respectively. The vapour pressure (P) of tetroxan has been measured over the temperature range 300–375°K. The results are summarized as

The results have been used in conjunction with previously published data to evaluate the entropy changes occurring in the system formaldehyde ⇌ trioxan ⇌ tetroxan ⇌ polyoxymethylene.
Polyhydrochinonsulfone. II.1. Poly[vinyl‐(2.5‐dihydroxy‐phenyl)‐sulfon]. Synthese von monomeren, homo‐ und copolymeren
Authors: Manecke Von Georg , Beyer Hans‐Jürgen 
Published: April 2003

AbstractVinyl‐[2.5‐diacetoxy‐phenyl]‐sulfon wurde dargestellt. Das Monomere wurde homopolymerisiert und mit Styrol sowie Styrol und Divinylbenzol durch radikalische Initiierung copolymerisiert. Nach Abspaltung der Acetyl‐Schutzgruppen resultierten Polymere, in denen die Redoxgruppe (Hydrochinon) über eine Sulfonbrücke direkt mit der Polymerenkette verbunden ist.
Partielle spezifische volumina von m.m′‐ditolyl und seinen oligomeren
Authors: Kern Von W. , Höcker H. , Heitz W. 
Published: April 2003

AbstractDas partielle spezifische Volumen von m.m′‐Ditolyl in Toluol wurde durch Dichtemessungen über den gesamten Konzentrationsbereich bei 25°C bestimmt. Das hieraus berechnete molare Überschußvolumen beträgt −0,21 cm3/Mol bei einem Volumenbruch von 0,5. Die partiellen spezifischen Volumina von Oligomeren des m.m′‐Ditolyls wurden in einem niedrigen Konzentrationsbereich in Toluol, Benzol und Trichloräthylen bei 25°C bestimmt. Sie sind in erster Näherung dem Molekulargewicht umgekehrt proportional.
Über die polymerisation von methacrylsäuremethylester mit α‐aryl‐(p‐toluylsulfonylmethyl)‐urethanen
Authors: Brachel Von Hanswilli V. , Engelhardt Fritz 
Published: April 2003

AbstractVerbindungen der allgemeinen Formel
magnified image
initiieren in Gegenwart von Kupfer(Il)‐ und Halogenid‐Ionen sowie von Sauerstoff die Polymerisation von ungesättigten Monomeren. Am Beispiel der Polymerisation des Methacrylsäuremethylesters wird die Abhängigkeit der Polymerisationsgeschwindigkeit von der Substitution des Initiators in R′ bestätigt und gezeigt, daß sie der HAMMETT‐Beziehung gehorcht.
Interaction of polylysine with phosvitin and nucleic acids
Authors: Roychoudhury K. , Biswas B. B. , Pal M. K. 
Published: April 2003

AbstractDNA dependent RNA asynthesis in inhibited by basic proteins like histones or polylysine This inhibitory effect is found to be suppressed by phosvitin, which is a phosphoprotein. Turbidometric studies indicate that polylysine interacts with DNA and RNA stoichiometrically. This interaction with DNA has been thought to be the cause of this inhibitory effect. Phovitin also interacts with polylysine more effectively than DNA. Phosvitin in quantities much less than the stoichionietric amount can compete with DNA for the polylysine and can thus make DNA free and available as template for the RNA synthesis. Phosphoserine, unlike pbosvitin, is ineffective in suppressing the inhibitory effect of polylysine.
Studies on organometallic compounds as polymerization catalysts. IV. Polymerization of propylene oxide catalyzed by zinc chloride‐alkali metal alkoxide system
Authors: Ishimori Michihro , Hsiue Ginho , Tsuruta Teiji 
Published: April 2003

AbstractBinary system of zinc chloride‐alkali metal alkoxide was studied as catalyst for propylene oxide polymerization. The reaction of zinc chloride with alkali metal alkoxide was found to proceed steppwise according to the equations:

Formation of high molecular weight polymer in the propylene oxide polymerization catalyzed by zinc chloride‐alkali metal alkoxide system is found to be caused by zinc dialkoxide formed in the reaction system. The results support our previous conclusion that the presence of alkyl‐zinc bond in zinc alkyl‐alcohol system is not necessarily an indispensable factor for high molecular weight polymer‐forming reaction.