bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermally‐induced cross‐linking of poly[2.2‐propane‐bis‐(4‐phenyl carbonate)]
Authors: Davis A. , Golden J. H. 
Published: April 2003

AbstractThe cross‐linking of poly [2.2‐propane‐bis‐(4‐phenyl carbonate)] by heating in a continuously evacuated system has been examined at various temperatures (295‐382°C). The effect of time and temperature on the viscosity of the polymer and the gel content is discussed.
Polyethylmethacrylate in dilute solution
Authors: Karunakaran K. , Santappa M. 
Published: April 2003

AbstractPolyethylmethacrylate (PEM) was prepared by bulk polymerization and fractionated using acetone/acetone‐water (2:1 V/V) mixture. The solution properties of fractionated as well as unfractionated polymers were investigated in various solvents (ethylacetabte, toluene, ethylacetate‐ethanol) by light scattering and viscosity at 35°C. Osmotic pressure measurements were also carried out on selected polymer samples for the evaluation of width of distribution. [η]–Mw and (r2)1/2–Mw relationships for these systems were established. Ethylacetate was found to be a bad solvent compared to toluene and methylethyketone. In the case of unfractionated PEM, the parameters like [η]2/3M1/3, Mw/[η], and Φ were corrected for molecular weight heterogeneity assuming SCHULZ‐ZIMM distribution. For the evaluation of FLORY's constant K, and the unperturbed dimension (r)1/2 of the polymer, FLORY‐FOX, KURATA‐STOCKMAYER, and STOCKMAYER‐FIXMAN methods were employed. The K and (r)1/2 values evaluated from the FLORY‐FOX method were almost similar to those measured in a Θ solvent, while the other two methods yielded higher values. A comparison of the measured (r2) and that calculated from KIRKWOOD‐RISEMAN and DEBYE‐BUECHE theories indicated the polymer coil as conforming to a statistical chain. The molecular weight dependence of A2, the second virial coefficient, for PEM/ethylacetate was established and the value of A2 compared well with that calculated from OROFINO‐FLORY equation.
Polyradikale mit verdazyl‐gruppen
Authors: Kinoshita Von Masayoshi , Schulz Rolf C. 
Published: April 2003

AbstractUm Polyradikale mit Verdazylgruppen zu gewinnen, wurden verschiedene Wege erprobt. Die Methylierung von Polyacrolein‐formazan führte nicht zum Ziel. Herstellung und Eigenschaften von 1.5‐Diphenyl‐3‐(p‐vinylphenyl)‐verdazyl werden beschrieben; eine radikalische Polymerisation dieser Verbindung war nicht möglich. Ausgehend von Poly‐p‐vinylbenzaldehyd gelang es aber, durch polymeranaloge Umsetzungen Polymere mit Verdazylgruppen darzustellen. Diese Polyradikale enthalten in jedem zweiten Grundbaustein ein ungepaartes Elektron.
Isolierung und charakterisierung von cyclischen oligomeren des formaldehyds
Authors: Burg Von K. H. , Hermann H. D. , Rehling H. 
Published: April 2003

AbstractBei der Aufarbeitung von Rückständen aus der Polymerisation von Trioxan konnten neben Trioxan und Tetroxan auch höhere cyclische Oligomere des Formaldehyds isoliert werden. Das Pentamere wurde dabei mit Hilfe der präparativen Gaschromatographie gewonnen, während zur Isolierung eines Ringes mit 15 Formaldehydeinheiten die Methode des Zonenschmelzens geeignet war. Die durch saure Agentien katalysierte Pyrolyse von Polytrioxan führt ebenfalls zu höheren cyclischen Oligomeren des Formaldehyds. Durch pyrolse‐gaschromatographische Untersuchungen wurde die Bildung von Pentoxan sichergestellt und das Entstehen von Hexoxan wahrscheinlich gemacht. Zur Charakterisierung der isolierten ringfömigen Acetale wurden ihre Polymerisierbarkeit, ihre Schmelzpunkte und ihre IR‐, Kernresonanz‐ und Massenspektren herangezogen.
Polymerization of styrene oxide and butadiene monoxide by organozinc compounds
Authors: Tsuruta Teiji , Inoue Shohei , Tsubaki Kazumi 
Published: April 2003

AbstractThe reaction of styrene oxide with organozinc compounds was studied to clarify the polymerization mechanism of styrene oxide. In the reaction with diethylzine ring scission of styrene oxide was observed to occur almost exclusively at the CH(C6H5)O‐bond to form ethylzinc monoalkoxide. In the second step zinc dialkoxide was formed by the reaction of the ethylzinc monoalkoxide with styrene oxide and the dialkoxide was found to be active species for the polymerization of styrene oxide. In the reaction of styrene oxide with zinc dialkoxide both α‐scission and β‐scission occurred. Studies were also made for butadiene monoxide.
The thermal degradation of polyoxymethylene
Authors: Grassie N. , Roche R. S. 
Published: April 2003

AbstractThe thermal degradation of polyoxymethylene has been studied in the dynamic molecular still. The energy of activation for the degradation of hydroxyl group terminated polymer increases from 5–7 kcal/mole in the early stages to 50–52 kcal/mole from about 40% volatilisation onwards. There is an inverse relationship between molecular weight and initial rate and this, together with the changes in molecular weight which occur during the course of the reaction and the fact that acetylation of the chain terminal hydroxyl groups inhibits the reaction, indicates a very close similarity between the overall reaction mechanism and that for the thermal degradation of poly(methyl methacrylate).From the shape of the rate curve obtained during the course of the reaction and the fact that the density of the residual polymer increases during the reaction it has been concluded that reaction occurs preferentially in the amorphous regions of the polymer.Molecular, free radical and ionic mechanisms have been considered in detail. An examination of minor reaction products and the effect of catalysts and inhibitors positively eliminates the possibility that a radical process is involved. In the presence of basic catalysts the reaction is undoubtedly anionic but the anionic and molecular mechanisms are virtually indistinguishable in the uncatalysed reaction although the molecular mechanism is preferred on energetic grounds.
Quantitative IR‐spektroskopische untersuchungen der mikrostruktur von polyvinylchlorid
Authors: Pohl Von H. U. , Hummel D. O. 
Published: April 2003

AbstractDie durch graphische Auftrennung des ν(CCI)‐Bandenkomplexes gewonnenen relativen integralen Extinktionen von ν(CCI)‐Schwingungen wurden in Abhängigkeit von der Polymerisationstemperatur des PVC untersucht. Der Grad der Syndiotaxie der Proben wurde ohne Erhitzung aus der relativen Intensität der ν(CCI)‐Schwingungen bestimint. Aus der Intensität der A1‐ und Bi‐Schwingungen bei 639 und 603 cm−l wurde die intramolekulare Ordnung der Ketten (Regalarität) und die für die Aufspaltung notwendige Mindestlänge der syndiotaktischen Zickzack‐Kette bestimint. Sic beträgt für Harnstoffeinschluß‐PVC 8 und für alle übrigen Proben 5 Monomer‐Einheiten.
Structural studies of polyesters. I. Crystal structure of polyglycolide
Authors: Chatani Yôzô , Suehiro Kazuaki , Ôkita Yasuo , Tadokoro Hiroyuki , Chujo Kiyoshi 
Published: April 2003

AbstractIn the course of structural study of aliphatic polyesters, the crystal structure of polyglycolide, the simplest polyester of the type [(CH2)zCOO]n was determined by interpretation of the X‐ray diffraction patterns of the fibers. The crystallographic data are: a = 5.22 Å, b = 6.19 Å, c (fiber axis) = 7.02 Å, the orthorhombic spacegroup, Pcmn‐D. Two molecular chains pass through the unit cell. The crystal structure was determined by the help of two dimensional and three dimensional FOURIER syntheses. The planar zig‐zag chain molecules form a sheet structure parallel to the ac plane and have not the polyethylene type arrangement. High density of the crystallite, 1.69 g/cm3, namely the tight molecular packing and the close approach of the ester groups might stabilize the crystal lattice and contribute to the high melting point of this polymer.
Thermal degradation of polymethylmethacrylate. Energies of activation
Authors: Jellinek H. H. G. , Luh Ming Dean 
Published: April 2003

AbstractRate constants of the thermal degradation of polymethylmethacrylate fractions have been measured over a range of temperatures, and the ARRHENIUS equations have been derived. There are two degradation reactions for this polymer; one “fast” reaction, which is chain‐end initiated, due to double‐bonded chain‐end polymer molecules and one “slow” reaction, which is initiated at random. The energy of activation for the fast reaction is much smaller than that of the slow reaction. Both show two levels of energies of activation proceeding from long to short chains. These energies of activation increase with decreasing chain length of the polymer as expected from theory. Whereas the differences in energies for the fast reaction are in agreement with a mechanism consisting of chain‐end initiation, depropagation, and second‐order termination, a reasonable value for the overall energy for the slow reaction is only obtained for a first‐order termination process. Such a reaction is not unlikely, as the polymer film contains appreciable amounts of monomer at this stage of degradation. The energies of activation for the slow reaction increase with percentage conversion as long as some double‐bonded chain ends are still in the system. It has to be concluded that the degradation of isotactic and syndiotactic polymethylmethacrylate, which degrade by random initiation, also have a first‐order termination reaction. On the basis of the results reported here, the confusion in the literature concerning energies of activation for the thermal degradation of polymethylmethacrylate can be understood. These energies do not only depend on chain length but also on the mechanism of the degradation process, range of conversion, and percentage of double‐bonded chain ends in the system.
Synthesis and properties of some poly(methyl)methacrylate stereoisomers
Authors: Berghmans H. , Smets G. 
Published: April 2003

AbstractThe synthesis of some new stereoisomer poly(methyl methacrylates) is described, and their structure discussed.In the polymerization of methyl methacrylate, initiated by phenyl magnesium bromide and anhydrous cobaltous chloride, polymers with a stereoblock structure are formed. On the basis of NMR spectra, a model can be proposed in which the polymer chains are composed of an isotactic sequency followed by a statistical one. An initiation and propagation mechanism are presented in order to interprete these data.The results of the study of the viscoelastic behaviour of the stereoisomers reported elsewhere are briefly summarized.
Phosphororganische Verbindungen. 60. Mitt. Aufbau und Eigenschaften eines optisch aktiven Anionenaustauschers mit identischem Chiralitäts‐ und Ladungszentrum
Authors: Horner Von Leopold , Balzer Wolf‐Dieter 
Published: April 2003

AbstractChlormethyliertes Polystyrol (vernetzt mit 0,5% Divinylbenzol) wird mit (+)‐Methyl‐ n‐propyl‐phenyl‐phosphin quartärisiert. Der entstehende Austauscher besitzt eine Kapazität von 2,68 mVal/g. Mandelsäure, Atrolactinsäure und Traubensäure konnten an diesem Material nicht in die Antipoden gespalten werden.
The Compressibility of Crosslinked Polymers
Authors: Warfield R. W. 
Published: April 2003

AbstractBulk compressibilities of seven crosslinked polymers have been measured at pressures as high as 20,000 atmospheres and over the temperature range 25 to 250°C. Volume changes of up to 20% were observed. In most cases the pressure vs. change in volume isotherms were nonlinear and the coefficients of compressibility at one atmosphere increased with increasing temperature. For many of the polymers, pressure‐induced glass transitions are observed. From data on the pressure and temperature dependence of the glass transition, glass‐rubber phase diagrams have been prepared. The nature of the compressibility process is qualitatively discussed in terms of the BUECHE theory. It is shown that the EHRENFEST relationship dTg/dP ≃ TVΔα/ΔCp holds for crosslinked polymers.
NMR studies of polymer solutions. VI. Molecular weight determination of poly(ethylene glycol) by NMR analysis of near‐end groups
Authors: Liu Kang‐Jen 
Published: April 2003

AbstractWe have used the chemically identical “near‐end” groups of poly(ethylene glycols) (PEG) for molecular weight determinations. High resolution NMR technique was used for all measurements. The number average molecular weight of the polymer can be calculated by measuring the ratio of NMR absorptions of chain segments in a polymeric structure to those of non‐polymeric segments (“near‐end” groups). Two and four internal ethylene groups of PEG can be used as the “near‐end” groups respectively in pyridine on the one hand, and benzene or α‐chloronaphthalene solutions on the other. It is clearly shown that the NMR absorption of the “near‐end” groups of PEG is a much better choice than that of the “end” group for molecular weight determination. We have also discussed the significance of realizing the effect of the “near‐end” groups on polymer NMR spectroscopy.
Condensation polymers and copolymers of N.N′‐bis(2.3‐epoxypropyl)piperazine
Authors: Canonica L. , Cappuccio V. , Caldo C. , Bonvicini A. , Cantatore G. , Maltese P. , Cicchetti O. 
Published: April 2003

AbstractCondensation polymers and copolymers are obtained by reaction of N.N′‐bis(2.3‐epoxypropyl)piperazine with primary aliphatic and aromatic amines, and with aliphatic, aromatic, cycloaliphatic, heterocyclic disecondary diamines.The reaction rates of the polycondensations of N.N′‐bis(2.3‐epoxypropyl)piperazine with primary amines rise with decreasing the chain length.In hydrocarbon solvents polycondensation reactions proceed slowly whereas in alcohols they are accelerated.Activation energies are 11.6 kcal/mole in the polycondensation with trans 2.5‐dimethylpiperazine, 12.6 kcal/mole with n‐dodecylamine, 16.5 kcal/mole with piperazine.
Viscosity‐molecular weight relationships for poly p‐chlorostyrene
Authors: Mohite R. B. , Gundiah S. , Kapur S. L. 
Published: April 2003

AbstractViscosity, osmotic pressure and light scattering measurements have been carried out on fractions of poly p‐chlorostyrene. The viscosity‐molecular weight relationships have been established. The KUHN‐HOUWINK constants obtained by different workers show wide divergence. However, the constant KΘ obtained by different workers from different extrapolation methods, is in good agreement with the value of 5.2·10−4. The same value is obtained using [η]R, the ordinate at the common point of intersection of the In ηr/c vs. c Plots for the same polymer in different solvents.
Participation of the depropagation reaction in the cationic copolymerization of 3.3‐bischloromethyl oxacyclobutane and tetrahydrofuran
Authors: Yamashita Yuya , Kasahara Hideo , Suyama Katsuhiko , Okada Masahiko 
Published: April 2003

AbstractA copolymer composition equation including the depropagation reaction was derived and applied to the cationic copolymerization of 3.3‐bischloromethyl oxacyclobutane and tetrahydrofuran. The observed decrease of the number of tetrahydrofuran units incoroporated in the copolymer with increase of the polymerization temperature or with decease of the monomer concentration was well explained by the equation. Differences between the catalyst systems, BF3·Et2O, Et3OBF4,PhN2PF6, and AlEt3H2O were also observed.
Ein automatisches viskosimeter zur flüssigkeitschromatographie
Authors: Meyerhoff Von G. 
Published: April 2003

AbstractEine Viskosimeterapparatur wird beschrieben, die ein automatisches sukzessives Einfüllen und Meessen von Flüssigkeiten erlaubt. Bei chromatographischen Prozessen ermöglicht es das Gerät, außer der bisher üblichen Verfolgung der Konzentration auch das Molekulargewicht des gelösten Stoffes im Eluat zu bestimmen. Für eine Elutionsgeschwindigkeit von 1 ml/min ist es möglich, das mittlere viskosimetrische Molekulargewicht in Intervallen von jeweils 2 ml oder auch 1 ml für den gesamten Elutionsvorgang anzugeben.
Kinetics and mechanism of the alkali‐catalysed addition of formaldehyde to phenol and substituted phenols
Authors: Eapen K. C. , Yeddanapalli L. M. 
Published: April 2003

AbstractIn view of the differences in the positional reactivities, reported by different authors, in phenol and methylol phenols, an exhaustive kinetic study using quantitative paper chromatography has been carried out not only on phenol and methylol phenols but also on phenols with methyl group and chlorine atom substituents.The o‐position is less reactive than the p‐position in phenol and substituted phenols for the addition of formaldehyde in the presence of alkali catalyst, with a correspondingly higher activation energy. The effect of the methylol group appears to be intermediate between the activating effect of the electron repelling methyl group and the deactivating effect of the electron attracting chlorine atom. But the marked activating effect of the methyl and methylol group in the o‐position is tried to be accounted for by intra‐molecular hydrogen bonding. The activating effect of chlorine atom in the o‐position is explained in terms of the electron repulsion between chlorine atom and the phenoxide anion.The few characteristic differences in the positional reactivities observed in the results of earlier workers are not found in the results obtained in the present investigation.
Kinetics and mechanism of the alkali‐catalysed addition of formaldehyde to dihydroxydiphenyl methanes
Authors: Francis D. Joseph , Yeddanapalli L. M. 
Published: April 2003

AbstractThe kinetics of the alkali‐catalysed addition of formaldehyde to dihydroxydiphenyl methanes (DPMs) has been studied by quantitative paper chromatography. The order of reactivity of the three DPMs is found to be o.p′‐ > p.p′‐ > o.o′‐DPM. The low reactivity of o.o′‐DPM is explained on the basis of formation of a chelate ring in its singly ionised form, resulting in the fixation of the negative charge on the O.Equimolecular quantities of p.p′‐DPM and formaldehyde (concentrations 0.04 M) react in presence of NaOH (0.006 M) to give 3‐methylol‐4.4′‐DPM. Under similar conditions o.p′‐DPM gave 3‐methylol‐2.4′‐DPM, 5‐methylol‐2.4′‐DPM and 3‐methylol‐2′.4‐DPM and o.o′‐DPM gave 3‐methylol‐2.2′‐DPM and 5‐methylol‐2.2′‐DPM. The individual rate of formation of each of the products is determined. These rates are compared with those of other reactions in the phenol‐formaldehyde reaction, and their relative importance in the overall reaction is discussed.
Graft polymerization in solution of methyl acrylate on atactic polypropylene
Authors: Natta G. , Severini F. , Pegoraro M. , Tavazzani C. 
Published: April 2003

AbstractThe polymerization of methyl acrylate in an atactic polypropylene solution in the presence of radical initiators (benzoylperoxide, tert‐butylperpivalte, α.α′‐azoisobutyronitrile, Iauroylperoxide) yields a mixture of grafted polymethylacrylate/polypropylene copolymer and a methyl acrylate homopolymer.The crude polymers are fractionated and the influence of the concentration of both monomer and initiator, and of the type ofsolvent used on the percentage of grafting was studied.The concentration of active macroradicals in the grafting reaction is measured with the of a slinplified kinetic scheme.
The decomposition of potassium peroxydisulphate in polymerization systems
Authors: Morris Carolyn E. M. , Parts Adolf Gustav 
Published: April 2003

AbstractThe influence of various soaps and monomers on the rate of thermal decomposition of potassium peroxydisulphate has been investigated. It was found that all investigated compounds, except a fully fluorinated soap caused marked increases in the rate or peroxydisulphate disappearance. This finding should be considered in studies on the kinetics of polymerization in which peroxydisulphate is the initiator.
Die chemische heterogenität von copolymerisaten. 4. Experimentelle untersuchungen zur verträglichkeit
Authors: Kollinsky Von Fritz , Markert Gerhard 
Published: April 2003

AbstractZwei chemisch einheitliche Methylmethacrylat/Butylacrylat‐Copolymerisate bilden in Substanz nur dann optisch homogene, d. h. klare Gemische, wenn der Unterschied im Methylmethacrylat‐Anteil 10–20 Mol‐% nicht übersteigt.Wie Torsionsschwingungsversuche zeigen, liegt die Grenze der mechanischen Homogenität bei der gleichen Differenz im Methylmethacrylat‐Anteil. Bei inhomogenen Systemen aus zwei einheitlichen Copolymerisaten werden zwei diesen entsprechende Dämpfungsmaxima gefunden.Elektronenmikroskopische Aufnahmen lassen zum Teil auch in optisch order mechanisch homogenen Systemen Strukturen noch in der Größenordnung von 30 Å erkennen. In der Nähe der Trübungsgrenze steigt die Phasengröße sprunghaft an. Bei Mischungen aus drei Komponenten übt das hinsichtlich seiner Zusammensetzung in der Mitte liegende Copolymerisat keine Verträglichkeitsvermittlung aus.In Copolymerisaten mit breiter, lückenloser chemischer Verteilung bilden sich Mikrophasen aus jeweils miteinander verträglichen Makromolekülen. Optische und mechanische Homogenität oder Inhomogenität ist dann eine Frage der Größe der einzelnen Mikrophasen. Unterdrückung bzw. Begünstigung der Übertragungsreaktion am Polymeren hat eine Vergröberung bzw. Verfeinerung der Mikrophasen zur Folge. In Übereinstimmung damit wirken Pfropfcopolymerisate homogenisierend.Orientierende Versuche an Copolymerisaten aus anderen Monomeren lassen darauf schließen, daß diese Feststellungen allgemeine Gültigkeit besitzen.
Darstellung und eigenschaften von poly‐4‐vinyltriarylmethylradikalen
Authors: Braun Von Dietrich , Faust Raimund Josef 
Published: April 2003

AbstractAls Ausgangsverbindungen für die Darstellung von Poly‐4‐vinyltriarylmethylradikalen werden die aus Poly‐4‐vinyltriarylcarbinolen zugänglichen Poly‐4‐vinyltriarylmethylchloride verwendt. Die Umsetzung der Poly‐4‐vinyltriarylmethylchloride mit Zinkpulver führt nur bei vollständigem Wasserausschluß zu den entsprechenden Poly‐Kohlenstoffradikalen; bei Anwesenheit von Spuren Wasser Entstehen Dagegen Poly‐4‐vinyltriarylmethylkationen.Die dargestellten Poly‐4‐vinyltriarylmethylradikale enthalten nach ESR‐spektroskopischen Untersuchungen bis zu 100 Radikalstellen pro Markomolekül. Sie reagieren mit Sauerstoff zu vernetzten Poly‐Peroxiden, wobei als Zwischenstufe ESR‐spektroskopisch instabile Peroxyradikale nachgewiesen werden können. Mit Alkalimetallen bilden die Poly‐4‐vinyltriarylmethylradikale Polyanionen und im Falle von Polymeren mit Biphenylgruppen außerdem Polyradikalanionen.
Triazin‐polymere. I. Poly(vinylenphenylentriazine)
Authors: Elias Von Hans‐Georg , Greth Erich 
Published: April 2003

AbstractBei der Kondensation von Methyl‐s‐triazinen mit aromatischen Aldehyden in konz. Schwefelsäure zwischen 25 und 60°C wurden Styryltriazine mit Ausbeuten bis zu 99% erhalten, darunter folgende neue Verbindungen: 2‐Methyl‐4.6‐distyryl‐s‐triazin, 2.4‐Dimetyl‐6‐styryl‐s‐triazin, 2.4‐Diphenyl‐6‐styryl‐s‐triazin, 2‐Methyl‐4‐phenyl‐6‐styryl‐s‐triazin, β.β'‐Bis(diphenyl‐s‐triazinyl)‐p‐divinylbenzol, 2‐(4‐Formylstyryl)‐4.6‐diphenyl‐s‐triazin, 2.4‐Diphenyl‐6‐(4‐nitrostyryl)‐s‐triazin 2.4‐Diphenyl‐6‐(4‐dimethylarminostyryl)‐s‐triazin, 2.4‐Diphenyl‐6‐(4‐chlorstyryl)‐s‐triazin und 2.4‐Diphenyl‐6‐(4‐methoxystyryl)‐s‐triazin. Kondensationstemperaturen von 100°C führten ‐ vermutlich durch Sulfurierungzu laugenlöslichen Produkten. Durch Polykondensation von Terephthalaldehyd mit 2.4‐Dimethyl‐6‐phenyl‐s‐triazin wurden in konz. Schwefelsäure lösliche, mit 2.4.6‐Trimethyl‐s‐triazin unlösliche Polymere erhalten. Die Polymeren sind nach ultraviolettspektroskopischen Messungen nicht durchgehend konjugiert. Die Geschwindigkeitskonstanten der Kondensation verschiedener s‐Triazine mit aromatischen Aldehyden wurden bestimmt. Die höchsten inhärenten Viskositäten betrugen ca. 130 ml/g (25°C, konz. Schwefelsäure), was Zahlenmitteln des Polymerisationsgrades von ca. 11 entspricht. Höhere Polymerisationsgrade konnten wegen Nebenreaktionen der Methylendgruppen nicht erreicht werden.